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Fixed vs Variable in Low Light

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 11:53
gpshumway View Drop Down
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Warning: long winded intro. Those with A.D.D. should skip to the Cliff's notes section below.

As I was texting my cousin in his deer stand this season, my wife out of the blue tells me she might like to go deer hunting next year. (She loves venison) She can count on one hand the times she's shot a gun, and I haven't been hunting in 20 years, so I'm undoubtedly rusty, very rusty. I'm considering buying the gear for this endeavor as a Christmas gift, but the cost is adding up quickly. I'm thinking we'd need three rifles and scopes to do this right, two hunting rigs and a target rig to help her learn to shoot and for me to shake the rust off. The target rig I've got a decent handle on, at least the optic part. While the purchase of the hunting rigs is some time off, I'd like to have a good idea in my mind of what to buy in case a great sale comes along or something pops up on the sample list.

My wife can be a bit excitable, and hasn't the greatest situational awareness in the world, so gear that's simple to use helps maximize her chance of success. I too have a preference for simple gear.  I'd much rather be a proficient user of simple gear than a fumbling user of complex gear. Murphy's law ensures that if I have a variable power scope, I'll use it to scan the tree line at high magnification, then forget to turn it down. Just then a trophy buck will walk out of the woods 30 yards from me and I won't be able to target it in time because I've forgotten to turn my magnification down. So, all other things being equal, I'd actually prefer a good fixed 6x scope to the more common 3-9 or 3-12 configurations. That puts me in a bit of a conundrum.

I've been reading ILya Koshkin's opticsthoughts.com site with great interest, and I'm a big fan of his "meat and potatoes" philosophy. In his review of the 10x42 Sightron and SWFA scopes he says "You often get better quality for the money since the whole system is less complex and easier to optimize (although with fixed power scopes being less popular than in the past, the economies of scale are working against you.)" So, theoretically the simpler optical design of a fixed scope should give you higher optical quality at the same price, but the fact that manufacturers sell so many more variable scopes will allow them to amortize the design and tooling costs over greater production numbers, lowering the cost of variable power scopes. So my question is, how much value do you get in a fixed power scope? Do you get any benefit choosing a fixed power in mid priced ($300-$600) hunting scope?

Here in Minnesota deer are often taken at the limits of legal light, so a scope's low light performance is paramount. I've seen said many times that objective size is important for low light performance and that makes sense, but factors like glass and coatings obviously play a role. I'm sure there are some 40mm scopes which outperform most 50mm scopes in low light. But this adds to the fixed versus variable confusion. Fixed 6x scopes with objectives larger than 42mm seem very rare, while variables of similar magnification with 50mm or even 56mm objectives are readily available in the same price range.

As an example, Meopta offers three scopes in their MeoPro range which I might consider. The 6x42 and the 3-9x50 seem to be priced identically at $600 (street). Presumably the 6x42 performs better in categories like sharpness, contrast and color fringing, but what about low light? Doesn't the 50mm objective give the 3-9x50 an advantage? I'm willing to deal with moderate increases in artifacts, especially at the perimeter of the sight picture, if it means better low light performance. I'm also willing to deal with a magnification knob which I might mis-adjust for the circumstances.

My second question is about the point of diminishing returns. There's a 3-9x40 scope in the aforementioned MeoPro line which costs $150 less than the 6x42 and 3-9x50 offerings. That scope I believe is re-branded as a major retailer's store brand, and frequently on sale for less than half the price of the 6x42 and 3-9x50. I took a look through said major retailer's scope this weekend and initial impressions were very positive, though in the brightly lit store it's obviously impossible to evaluate low-light performance. How much practical improvement in performance can I expect for the substantial increase in cost of the 3-9x50 or 6x42 options? How many extra minutes of visibility through the scope at dawn and dusk will I really get? This is not a prestige purchase for me, it's a purely utilitarian device.

I'm not wedded to Meopta either. The SWFA SS has an enviable reputation for quality and value, and the 6x42 version is right in my price range. I'd deal with the target turrets and the heavy weight if its the best value for my needs. The IOR Valdada 6x42 seems to have a good reputation, but like the higher-end Meoptas, it's at the upper end of my price range. There's also the Leupold FX3 6x40, which I suspect is overpriced given the Leupold name, and its field of view is fairly poor, but if you guys say it's a standout performer in low light I'll consider it. I'm also not opposed to trolling for some used gear, say the old Nikon Monarch 6x42 or Sightron 6x42 scopes which have gone out of production. I suspect they could be a great buy.

When it comes to reticles, I have a preference for evenly divided reticles like mil-dot for ranging and holdover. I don't prefer ballistic type reticles as variables like caliber and bullet weight make them less useful. Any complex reticle is supurfuluous at Minnesota deer ranges, but a mil-dot type might be useful if we choose to hunt the western plains.  Really a good narrow centered heavy duplex reticle is probably the best.

Basically my priorities come down to this:

- Low light performance

- Value for money

- Simplicity

- Field of view (if fixed power)

- Light weight

Help me out with a short list of candidates, and thanks so much for your help!


Cliff's notes:

Looking for good, high-value scope for deer hunting in the Minnesota woods. Emphasis on low-light performance, simplicity and light weight. Prefer fixed 5-7 power for simplicity. Budget ~$450.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 17:13
koshkin View Drop Down
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Hunting pigs at night screams thick or illuminated reticles and large objective lenses.  Meopta is a good palce to start, but it is hard to find much in the sub-$450 range with Meopta.  That having been said, I think you could do really well with MeoPro 6x42 or MeoStar 7x56RD, if you can stretch your budget sufficiently.

In terms of overall image quality in low light, there is little to differentiate similarly priced fixed and variable scopes, so I would not occupy myself with that too much. 

Another option, which also involves stretching your budget a bit (but less than with Meopta) is Leupold VX-R 3-9x40.  While optically, it is not as good as the Meopta, it is very respectable and the illuminated reticle will prove extremely valuable.  In low ight in overcast areas, reticle visibility is often a bigger problem than target visibility.

Leupold FX-3 is a very good design as well that is actually in your price range.  While personally, I would rather lean toward the options above, a 6x42 FX-3 with a heavy duplex reticle is a very respectable way to go.

If I were you, I would spend some time gong through the samplelist.

ILya




Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 17:57
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I personally think it would be a waste of money to build 3 rifles. If you just want 3 build 3. But if your goal of one is to teach your wife to shoot, then I say decide the two rifles you want for hunting and spent the extra from the third rifle on better scopes for the two. Then practice with said rifle so as to be more comfortable with it. You could buy a lower power scope with the same retical to practice with but I would only buy two rifles and use the extra money making them to my exact desire.

It is better to be more comfortable with your primary than to have a Secondary you wish you had brought to the woods...
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 20:21
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Thanks for the reply, ILya.

I'm not sure where you got nocturnal pig hunting, some other post maybe?  I'm talking about white tail deer hunting.  The legal limits are half an hour before sunrise and half an hour after sunset.  Here in the north woods twilight lasts a while.

From your comments it seems the point of diminishing returns I'm seeking is actually at or above my preferred $600 maximum, is that correct? When one steps up in price what benefits in low light does one get?  I'm assuming the $1250 S&B 6x42 is an excellent scope, but that I'd need to see it side by side with the Meopta 6x42 to see the difference, am I correct?  Basically I'm looking for a scope one step above the "I can tell without comparing side by side" level.  Make sense?

The MeoStar 7x56RD looks like an excellent scope, it has a FOV only slightly narrower than a good 6x, and wider than the Leupold FX-3.  Problem is I can't seem to find it anywhere, does SWFA carry it but not list it on the website?  I realize this is SWFA's forum and I don't want to step on their toes.  When you say "stretch the budget", how far exactly?

dwbarnette-
You may be right about the target gun, but there were a lot of factors behind considering it.  It would be a heavy barrel .223 to allow for lots of target practice without barrel heat causing POI shift.  This means it would be heavier than I'd really like to lug into the woods or shoot off hand, but would also be in a cartridge which is a little light for taking northern white tails.  I of course chose .223 because quality ammo is about half the cost of any other center fire caliber (Hornady steel match) 

Deer season won't start until next November and I'd likely sell the .223 target gun to finance the hunting guns if I felt it had served its purpose.  I'm not planning on buying the hunting guns until next fall and we're sure it's something we want to commit to. The target gun would be the Christmas present.  But, if the optic transfers from the target gun to one of the hunting guns, so much the better.  Make sense?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 20:34
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First please check on your state hunting laws to determine what calibers are legal to use for deer there.  I will suggest you purchase a Tikka T3 rifle in 7mm08 this is a 308 case necked down to 7mm.
If you are unable to find that step up to a 30-06 because there are many choices of factory ammo suitable for different purposes.  I would set the Tikka rifle up with one of these two scopes, and I would zero it for 200 yds then practice at 50,  100,  200, 300 to know where it hits at those distances.
Trijicon 1-6x24 AccuPoint 30mm Rifle Scope Trijicon 1-6x24 AccuPoint 30mm Rifle Scope
Stock # - TR25C200090
  • Matte
  • Red Triangle Post
  • 30mm
  • Trijicon Logo Sticker
  • Lenspen
  • Set of Lenscaps
  • AccuPoint Manual
  • Warranty Card
$1,190.00

Trijicon 2.5-12.5x42 AccuPoint 30mm Rifle Scope Trijicon 2.5-12.5x42 AccuPoint 30mm Rifle Scope
Stock # - TR26C200107
  • Matte
  • Green Triangle Post
  • 30mm
  • Side Focus
  • Trijicon Logo Sticker
  • Lenspen
  • Set of Lenscaps
  • AccuPoint Manual
  • Warranty Card
$1,105.00

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 20:42
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My wife shoots the deer with the scope on whatever mag level it was when handed to her. Just get a variable and leave it turned down. She killed her first at around 150+ yards with the scope set to 1.5x. Drilled it perfectly and had no idea there was another way.

I will say this and I'm not trying to be impolite. Women are more likely to have bucks approach them at very close range. A fixed 6x or even 4x will leave her with a scope full of brown and no way of knowing where to hold. Most long time hunters I know have at least one story of trying to sight down the side of the barrel because 3x was too much. My wife has more than one story like that and she doesn't hunt much. Her next scope will start at 2x.

If you're trying to contain spending, I would suggest a .22lr sporter matched to the deer rifle. Put a picatinny rail on both and swap the scope back and forth. Good scope, good rings, good rest and there's nothing to it the once a year you do it.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 20:45
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Another option is the Howa 1500(I own one myself) with heavy barrel. I have less than 500 with rifle bipods and scope mount. It comes in many different calibers. I plan to put the 10x42 SFWA SS Classic for a good med-long range with good mad light.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 20:45
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Med light
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 20:50
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For the second rifle -one for her -  I would pick a Savage and note the AXIS  XP comes in pink "Muddy Girl" in a 7mm08  I would use Talley ringmounts http://swfa.com/1-C1432.aspx
Redfield 2-7x33 Revolution Rifle Scope Redfield 2-7x33 Revolution Rifle Scope
Stock # - RED67080
  • Matte
  • 4-Plex
  • 1"
$179.95

If you want something to practice with that would be a 22 rifle but be sure you can find ammo first and I would probably pick a Ruger 10-22 possibly the take down model but that depends on what kind of money you want to invest  If 22 ammo is too difficult to find look for a used  SKS  that shoots  7.62x39 Russian cause the ammo is really cheap and it has very light recoil being semi auto,  these can be quite suitable for deer with open sights with a little practice. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 20:54
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I use this scope a lot for anything in low light - coyotes etc.
Trijicon 1-4x24 AccuPoint 30mm Rifle Scope Red Triangle Trijicon 1-4x24 AccuPoint 30mm Rifle Scope
Stock # - TR24R
  • Matte
  • Red Triangle
  • 30mm
$935.00
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 23:29
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I'd rather not turn this into a discussion of rifles and cartridges.  My wife would kill me if I suggested a pink gun because she's a girl, especially a cheap pink gun.  Bad juju. 

Minnesota allows any center fire rifle with caliber greater than .22 for deer hunting (.224 counts), so while I technically can use a .223 Remington to hunt deer, it's not my preferred cartridge. 

But that's all for later.  I want to talk scopes here, in particular those for low-light shooting in the $300-$600 range.  The field in that range is huge, how do I narrow it?  

From ILya's comments he likes Meopta for low light, and there's not much benefit to fixed power. so let's stick with Meopta for a moment.  How much performance is lost stepping down from the MeoPro 6x42 to the MeoPro 3-9x40? With the current sale the 3-9x40 is less than half the price.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/29/2016 at 23:42
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They are both meopros, so i dont think there is going to be much difference.

I have a meopta artemis 3/9xthat was their mid line before they changed it to meopro. Its a good scope, optics a quite good and it has held up well on a 7mag semi auto. For me it has alwys done well in legal shooting time light.

Leupold vx3 and vxr are great scopes too. If you get thr firedot illumintaion it is excellent in low light.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/30/2016 at 10:05
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Urimaginaryfrnd

Trijicon 1-6x24 AccuPoint 30mm Rifle ScopeTrijicon 1-6x24 AccuPoint 30mm Rifle Scope
Stock # - TR25C200090
  • Matte
  • Red Triangle Post
  • 30mm
  • Trijicon Logo Sticker
  • Lenspen
  • Set of Lenscaps
  • AccuPoint Manual
  • Warranty Card
$1,190.00


Trijicon 2.5-12.5x42 AccuPoint 30mm Rifle ScopeTrijicon 2.5-12.5x42 AccuPoint 30mm Rifle Scope
Stock # - TR26C200107
  • Matte
  • Green Triangle Post
  • 30mm
  • Side Focus
  • Trijicon Logo Sticker
  • Lenspen
  • Set of Lenscaps
  • AccuPoint Manual
  • Warranty Card
$1,105.00

These scopes are very interesting to me. I haven't looked at Trijicon in a while because the only scopes I ever looked at had such short eye relief that I was concerned about mounting them on larger calibers than a 223. Both these scopes in the Mill dot reticle seem to represent something that would be very useful to my style of hunting.

Do you or anyone else have any experience with these scopes at last legal hunting light? Looking at the specs of the 1-6 VS the 2.5-12 it looks like the 1-6 has a larger exit pupil at 1X than the 2.5 at low power. Not knowing how that changes through the spectrum I'm just wondering about your impressions of how easy both scopes are to get behind and how they compare in last light hunting.

Also do you know the size of the illuminated dot at 100 yards at full power and the size of the mill dots on the mill reticle. 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/30/2016 at 10:27
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Originally posted by gpshumway gpshumway wrote:

<span style="color: rgb49, 48, 43; font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 16.8px;">I'd rather not turn this into a discussion of rifles and cartridges.  </span><span style="color: rgb49, 48, 43; font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 16.8px;">My wife would kill me if I suggested a pink gun because she's a girl, especially a cheap pink gun.  Bad juju. </span>
<div style="color: rgb49, 48, 43; font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 16.8px;">
<div style="color: rgb49, 48, 43; font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 16.8px;">Minnesota allows any center fire rifle with caliber greater than .22 for deer hunting (.224 counts), so while I technically can use a .223 Remington to hunt deer, it's not my preferred cartridge. <div style="color: rgb49, 48, 43; font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 16.8px;">
<div style="color: rgb49, 48, 43; font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 16.8px;">But that's all for later.  I want to talk scopes here, in particular those for low-light shooting in the $300-$600 range.  The field in that range is huge, how do I narrow it?  <div style="color: rgb49, 48, 43; font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 16.8px;">
<div style="color: rgb49, 48, 43; font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 16.8px;">From ILya's comments he likes Meopta for low light, and there's not much benefit to fixed power. so let's stick with Meopta for a moment.  <span style="line-height: 16.8px;">How much performance is lost stepping down from the MeoPro 6x42 to the MeoPro 3-9x40? With the current sale the 3-9x40 is less than half the price.  </span>


For the money, I would grab the 3-9x40 MeoPro and be done with it.

Ilya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/30/2016 at 12:37
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Thanks, ILya.  I'll pick up the 3-9x40.  

I'm still interested in understanding the current point of diminishing returns in scope performance, and what makes for a good low light scope other than obvious things like an illuminated reticle.  

Just for fun last night I pulled out my old Simmons 4x crossbow scope (from my paintball gun) and looked through it.   I can't have paid more than $75 for this thing.  In the dark it was pretty useless, but I would expect most scopes to be useless at 7:00 pm in Minnesota this time of year.   Looking through it this morning it's not nearly as bad as I expected.  It's fairly awful to get behind and the optics are obviously poor in the outer quarter of the FOV, but the center seems serviceable.  If the other factors were well optimized, I could absolutely live with this level of optical artifacts.  By that I mean if the scope had good low light performance, were easy to get behind, had good FOV for its magnification and had a good reticle (possibly illuminated), the optical performance in the outer quarter of the FOV wouldn't really bother me.  Though I'd certainly be willing to pay more for better performance, that increase in performance wouldn't really help make the hunt more successful.   I'm going to look through the Simmons again tonight half an hour after sunset and see how awful it is.  

Help me understand the physics of low light performance.  
When it comes to light transmission, it seems like all decent scopes are about the same, with coatings that transmist 99.5%+ per lens surface.  So whether it's a $200 Burris Fullfield II or Meopta's new 8x56RD marketed as "Brightness Above all. From Twilight to Dead of Night.", the difference doesn't seem to be light transmission, but other parameters like contrast, MTF and distortion.  

ILya's ancient post here illudes to what actually makes a good low light scope, but doesn't get specific in how to choose one.  
http://www.opticstalk.com/light-transmission-question_topic847.html

How does objective size play into this?  Say you've got two scopes from the same manufacturer, but in different product lines.  Say the scopes are the same price, the lower product range scope is a 3-9x50 and the higher end scope is a 3-9x40, which is likely to give better low-light performance?  I don't want to get too bogged down in brands here, but I think you could pick a couple of Nikons from the higher end Prostaffs and lower end Monarchs which fit the above description.  Weaver makes Grand Slam scopes which present this choice as well.  Which is better for low light, the Grand Slam 3-12x50 or the Grand Slam 3-12x42?  They're within $5 of each other.  

Thanks again for all the input guys.  Regardless of the discussion I suspect I will be very happy with the MeoPro 3-9x40.  

Side note: It looks like Meopta has discontinued the 7x56RD.  It disappeared from their site between yesterday and today, replaced by the 8x56RD marked "New".  
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99.5% per lens surface.  Any scope company that claims that is lying.  I highly doubt that is even possible. 

There is a reason why we pay $1500 for a excellent low light optic.  Just because a company claims their $200 optics has 99% transmission doesn't mean it is comparable to a alpha optic. The lenses are not the same, the coatings are not the same, the optical design is not the same.  There are many levels of lenses and coatings.  It all depends upon how much the manufacturer wants to pay for said lenses and coating. 

My $200 Sightron binos don't even compare to my Meopta HDs in low light or even in day light.  And my Meopta HDs are not as good as my Zeiss victories either.   The difference between the sightrons and the Zeiss is huge, especially in low light. 
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Originally posted by supertool73 supertool73 wrote:

99.5% per lens surface.  Any scope company that claims that is lying.  I highly doubt that is even possible. 

I suggest you read this thread from 2004 which I quoted above:
http://www.opticstalk.com/light-transmission-question_topic847.html

Every lens has two surfaces and many scopes have five lenses, 99.5% to the tenth power gives the ~95% light transmission quoted by several makers.  It is possible, at least within a narrow range of wavelengths.  Again, read that old thread, it's a good read.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/01/2016 at 08:37
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3 rifles seems a bit much.

Get a sporter .22lr and a deer rifle.

(22lr: great for learning and developing the principles of marksmanship, cheap to shoot and you don't get physically tired).

Deer rifle, a few practise shots every session and then take it hunting.

Scope wise:

All things being equal, a fixed scope has better light transmission due to less lenses (a little less light gets through a each successive lense).

Reticle: a number 4 or duplex type (thick cross with a thinner middle section) and a single illuminated dot.

For hunting boar in Europe (done at night over bait when light transmission is paramount) the usual choice is a fixed 7x50 or 8x56 scope from Meopta or Swarovski / Schmidt & Bender / Zeiss
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/01/2016 at 09:07
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The MeoStar R1 7x56 RD is still produced and available from Meopta, but may not be in stock with Meopta USA or one of their dealers.  The MeoStar R2 8x56 RD has just been released (and now available) and thus the switchover on the Meopta USA website to the "latest and greatest".
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/01/2016 at 09:55
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Originally posted by gpshumway gpshumway wrote:

Originally posted by supertool73 supertool73 wrote:

99.5% per lens surface.  Any scope company that claims that is lying.  I highly doubt that is even possible. 

I suggest you read this thread from 2004 which I quoted above:
http://www.opticstalk.com/light-transmission-question_topic847.html

Every lens has two surfaces and many scopes have five lenses, 99.5% to the tenth power gives the ~95% light transmission quoted by several makers.  It is possible, at least within a narrow range of wavelengths.  Again, read that old thread, it's a good read.


Its easy for any company to publish a number.  There are lots of things that they may do different.  Do they measure for a single wavelength or an average across the entire spectrum?  There are also certain wavelengths that have little affect on what we see.  So they may be bragging up a wavelength that does zero good for us.  Because they don't have the knowledge, or technology to improve the ones that really affect what we see. 

Just because a brand may claim they have 95% total pass though does not mean it is going to look like a Zeiss HT that claims 95% passthrough. 

Often scopes have a lot more than 5 lenses as well.  A least variable scopes.  I bet complicated designs like Swaro Z6 and similar have a lot of lenses.  Then you have mutlicoated vs fully multicoated.  Most lower end scopes do not coat every single lens the same.  So while a couple of their lenses they may claim 99% I bet the others are not. 

I just have a hard time believing many of these statistics.  If Zeiss only claims 95% total light transmission on their best optics, then how is it even possible for a $200 scope to claim the same.

And maybe I am completely wrong, but I think most of the statistics we read are marketing gimmicks.  I own a pair of Zeiss Victory binos and I have looked through virutally all the other alpha brands side by side and many cheaper brands.  I have yet to see anything else have a brighter image to my eye.   
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I have a section in the Riflescope Fundamentals article I wrote many moons ago on light transmission.  The whole thing is here http://opticsthoughts.com/?page_id=122

Here is the whole section on optical quality:

Optical quality: good glass, bad glass, it’s all the same, isn’t it?

 

No, it is not the same. Not Quite. All you have to do to confirm that is get a couple of scopes with widely differing price tags but similar configurations and look through them side by side for a few minutes, preferably under some sort of challenging light conditions (not inside a gun store). However, comparing a $100 scope to a $3000 one sure looks like a rigged election, and it is. For products that are closer in price the differences are often quite small. Some companies offer more for the money than others, but overall, you get what you pay for. I’ll cover that in more detail further on, but, for the time being, it is worthwhile to talk a little bit about optical quality and image quality. A lot goes into making a riflescope with good optical quality: system design has to be properly worked out, all of the optical components have to be shaped and polished to very high standards, coatings have to applied both correctly and consistently, etc. However, from an end user perspective, none of those details by themselves should be of any interest. Still, I see internet discussion all over the place on how a particular scope features glass X which must be totally superior to glass Y. These discussions are largely a testament to how successful marketing departments of large equipment makers in diverting their customers’ attention from what is actually important and toward the useless, but cool-sounding details. I am not saying that the materials used are unimportant. They are important. However, they are not directly important. Moreover, the choice of materials is driven by the overall system design and no matter how high the quality of a particular piece is, it has to be used correctly. On top of that, some other part of the optical system may be the limiting factor. For example, there are three separate optical systems inside a typical riflescopes, eyepiece, relay and objective. All three are equally important, but if the eyepiece is badly designed, for example, it makes no difference how phenomenally good the objective lens system may be and vice versa. On top of that, as end users of the product we really do not know enough of the technical details of what goes into a particular scope to be able to make any sense of whether they matter or not. Once in a while, during a candid conversation with a scope maker they mention something that is actually worthwhile, but then they usually ask to keep this information private (and I understand why). Bottom line is that, first and foremost, we should be looking at the overall image quality of the product. Otherwise, we run the risk of “focusing on the trees so much, that we lose sight of the forest”. When it comes right down to it, the only truly relevant question about the optical quality of a riflescope is the following: “will you be able to see your target well enough to comfortably make a shot at all possible lighting and environmental conditions you might encounter?” If the answer is “yes”, do you care about how the scope maker achieved this? Unless you have a lot of money to spend on a scope, the answer is likely to be “no”. Then you just have to look and see which scope within your budget gets you the closest to “yes”. How the scope maker achieves that is still not especially relevant.

On the other hand, looking at this from the standpoint of those trying to sell their products in a very competitive market place, I can see why the advertisement campaigns we see are designed the way they are. After all, if you make a mid-range riflescope that is not very different from a half-dozen of your competitors, how do you make it stand out? You have to zero in on some sort of a differentiating features that touch on both optical and mechanical qualities of the product. Mechanical features are fairly simple: different knob and other control designs are easy to photograph, describe and put into an ad. How do you sell good image quality? Every magazine ad for every scope company for a riflescope talks about how well you can see. You pretty much have to tout something: patented coating recipe, extra low-dispersion glass, “high definition” glass, etc. None of these things by themselves are of any importance and (by my estimate) nearly 100% of what you see in a typical advertisement is, at best, misleading and at worst, pure BS. However, all these tricks are necessary for attracting enough attention to a particular product to at least get you to consider it.

Going forward, I’ll discuss a few things I look at when I evaluate a riflescope’s optical quality. I am not going to spend much time on scientific definitions of those terms. I think it is more pertinent to look at how they effect a scope’s performance.

 

Resolution and Contrast

First of all, I think it is worthwhile to define these two terms, if briefly, since they sometimes are confused with each other. Both refer to the image quality and are influenced by a number of optical design parameters. However, in order to evaluate resolution and brightness, you do not need to know anything about the scope’s construction. All you have to do is look through it and pay attention.
 

Resolution is simply the ability of the scope to distinguish small details within the image.

Contrast is the ability of the scope to faithfully transmit the difference between light and dark (and by extension color fidelity and saturation).

I have heard people say that resolution and contrast go hand in hand. That is not, strictly speaking, correct. They are in a perpetual match of “tug of war”. It is impossible to optimize both of them to be as high as possible. If resolution is fully optimized, contrast suffers, and vice versa. In an image with high resolution, but low contrast, there may be a lot of fine detail, but you might have a hard time distinguishing between them, since they do not stand out much.  Conversely, if an image has high contrast, but low resolution, all the large details will be very distinct (a common term is to say that they “pop” out at you), but small details will simply not be present. While ideally you would want to have an image with both high contrast and high resolution, that is not easy to achieve. For every optical system, the designer has to compromise between resolution and contrast in order to achieve a well-balanced image. Moreover, a riflescope’s contrast and resolution are typically not the same in the center of the image as they are near the edges. The term “sweetspot” usually refers to how large of a spot in the center of the image delivers consistent resolution and contrast (and a few other things). Historically, different companies chose to compromise between resolution and contrast in different ways. For example, between the “alpha” makers, historically, Zeiss used to always put a little more emphasis on resolution, Leica on contrast and Swarovski on sweetspot size. In practical terms, they naturally tried to get everything as well optimized as possible, but they simply had slightly different ides of what the “optimal” compromise is. In recent years, as the optical quality keeps on getting better and cheaper, there is some convergence between the compromises made by top end companies anyway. That is one of the reasons why some people prefer image quality of scopes from particular companies: since we all have different eyes, we are sensitive to different things. Some, for example, are so sensitive to contrast, that a very well resolved image might not look all that good to them due to somewhat muted contrast. Personally, I adjust to contrast differences pretty well, but my eyes favor (somewhat) high resolution and wide sweetspot (hence my affection for Zeiss riflescopes and Swarovski binoculars).

Moreover, the relative importance of contrast and resolution sometimes changes as the light gets low. In bright daylight, when the objects you are looking at are naturally very contrasty, even if the scope diminishes that contrast very well, you are still likely to see details pretty well. However, as the light gets low, if contrast is insufficient, fine details start blurring pretty quickly, and even large details become hard to see. They just do not stand out as much. In order for low light performance to be good, both resolution and contrast have to be up to par (and that is one of the reasons you get what you pay for).

Lastly, I’ll briefly mention MTF. MTF stands for “Modulation Transfer Function”. I see this term misused in all sorts of discussions related to sporting optics. MTF is, in essense, a composite measure that describes how well a particular optical instrument maintains contrast at ever increasing resolution and with respect to spatial variation within the image. Just about every optical design goes through some sort of MTF optimization, and a lot of the potential performance of an optic can be gleaned from its MTF curves. In principle. In practice, since the peculiarities of our eyes are not accounted for, there is no replacement for looking through the riflescope in question. Three years of digging through specs and curves will not replace 20 minutes of messing with the actual product.

If you are interested in more technical details on MTF, resolution and contrast, there are all sorts of wonderful online resources available: Wikipedia, Norman Koren’s website, etc. Just do not expect a whole lot of practical and applicable insight from them, since they are primarily focused on the photography applications, where image acquisition is accomplished via a well-characterized imaging sensor, not your eye. Bottom line is that all optical designers pay attention to MTF and optimize it the best their budgets allow.

 

Coatings and Light Transmission

There is really not all that much directly relevant information that I can say about coatings, but it is useful to know why they are important.

There are all sorts of coatings used in modern optical devices and for a number of different things. However, in the context of riflescopes, when someone says “coatings”, they usually mean anti-reflective coatings, often shortened into ARC or “AR Coatings”. These coatings minimize the reflections at every air-to-glass interface. If you happen to be looking at a riflescope that has both lenses and prisms (like Trijicon’s ACOG, for example), then the lenses have AR coatings on them, while the prisms, depending on which surface you are looking at, will have either Anti-Reflective coatings, or High-Reflection coatings (one of the surfaces of the roof prism). However, for the sake of this discussion, I will stick to AR Coatings.

First of all, there is the natural question of why we need these coatings at all.

The reason is quite simple: every time light passes through an interface between two different materials (like air and glass, for example), some of it gets reflected back. The exact amount of light that passes through vs the light that gets reflected back depends on the specifics of the materials in question, but for air-to-glass and glass-to-air interfaces it works out to be ~4% per surface (if there are no AR coatings involved). A riflescope has quite a few lenses in it and, assuming they are air-spaced, each lens has tow surfaces that reflect a little light. Let’s assume that we are dealing with a scope of fairly simple construction, like some fixed power designs, and it has 5 lenses, i.e. 10 reflective interfaces. If you want to calculate the total amount of light that gets through the scope, you simply trace through each interface sequentially: first surface lets through 96% of incoming light, next surface transmits 96% of that and so on. The effect is multiplicative, not additive. It is more convenient to write that for a scope with 10 surfaces:

[Total light out of the scope]=[Total light entering the scope]*[0.96^10]

Incidentally light transmission is defined as a ratio of light coming out of the scope to the light entering the scope. In this case, from the simple formula above:

Light Transmission=[0.96^10]=0.665 or 66.5%

If you have some sort of a decent quality Anti-Reflective coating on every surface in the scope, reflection at each interface can go down to 0.5% (or conversely light transmission at each interface becomes 99.5%). In that case, for the whole scope:
Light Transmission=[0.995^10]=0.951 or 95.1%

In reality the calculation is not as simple as that since there is some wavelength (color) dependence involved in addition to other considerations, but even if this is a “back of the napkin” approximation, there is still a lot more light getting through when decent coatings are involved, ~30% difference in this case.

Pretty much all modern scopes employ AR coatings of some sort, so when you compare them the difference in total light transmission is likely to be not huge. Perhaps more importantly, your eye is very good for adjusting to these small differences in total amount of light that the scope delivers to it. In modern scopes, total light transmission is not directly important. As a matter of fact, it is a lot more important to know how much light gets reflected than how much gets transmitted.

While your eye does not care too much about light transmission, it cares about image fidelity a great deal. If there are strong reflections somewhere within the scope, you can run into a situation where there all sorts so of reflections bouncing back and forth inside the scope. Some of that secondary reflected light eventually makes it to your eye and your brain finds it more difficult to make sense of the primary image. On the surface, it seems like the strength of that secondary reflected light is a fraction of a percent of the original imaging getting through the scope, but under some conditions, it can have quite an effect on the image. For example, imagine you are trying to take a shot at a shaded target some time around sunset looking toward it. As you look through your scope, you have both the shaded target and the very bright setting sunlight in your field of view. Because the bright sky during sunset is so much brighter than what you are actually aiming at, even a weak reflection can be sufficient to seriously degrade how well your eye resolves the target itself (this is a type of optical flair, which I will touch on in the next section).

Riflescope advertising often proudly touts a high light transmission ratio of a particular scope. Higher light transmission (i.e. fewer reflections) is usually a good thing, but it should be looked at in proper context. Image quality is highly dependent on how sophisticated the optical design of a scope is, and top notch designs often require more optical elements than simpler ones. With so many lenses inside the scope, the overall light transmission might drop a little (remember each extra surface reflects some extra light), but the image quality of that scope is likely to be higher than that of a similar scope with less sophisticated (i.e. fewer lenses) design, if they use the same AR coatings. The best example of that is offered by two, no longer available in US, Kahles scopes that I had a chance to compare side by side: Kahles CL 3-9×42 and Kahles KX 3-9×42. Both are excellent scopes, but the more expensive CL has an extra lens in it. Otherwise, these are very similar designs that use identical coatings (Kahles’ AMV). KX had slightly higher light transmission, while CL has higher overall image quality.

Lastly, there is the matter of objective lens diameter to address. I often hear people say that because scope X has larger objective lens than scope Y, it has higher light transmission. That is not necessarily correct.

A scope with a larger objective lens lets more light into the scope. However, light transmission is a ratio that is normalized with respect to the amount of light entering the scope. Hence, while a scope with a larger objective lens may very well deliver more light to your eye, light transmission ratio is no tin any way effected by it.

 

Stray Light, Scattering and Flare

Stray light is exactly what it sounds like. It is, quite simply, light that strays into the image from all sorts of different sources and that is not intended to be there. It is the unwanted light.
It can enter the image in a number of different ways:

  • reflected light (this is the light that is technically supposed to be entering the scope, but it follows an unintended path, as mentioned in the previous section),
  • off-axis light from outside the field of view that enters the objective lens at an angle and causes reflections from glass surfaces (veiling flare, for example)
  • scattered light from particles and glass impurities in the optical path
  • scattered and reflected light from mechanical structures inside the scope

 

Optimizing stray light performance of the scope is, often, one of the more important final touches in the design. If you look into the objective lens of a high quality riflescopes, you will note that all the metal surfaces inside look like they were sandblasted and blackened in some sort of a non-flaking way. If you pay attention you might also see some slight baffles that are strategically positioned to block off some off-axis light. Bottom line is that figuring out how to deal with stray light is mostly a problem for an optical designer; however, there are a few thing a shooter can do as well, to alleviate some of the problems. No matter how much effort goes into suppressing stray light, all scopes are susceptible to it, although to varying degrees.

First and foremost, if your scope came with a sunshade (metallic tube that can get screwed into the objective bell of a scope as an extension of sorts), use it. It might get in the way on a hunting rifle, when out in the field, but on other occasions, I suggest giving it a shot. Other than the scope being slightly longer, there is really no downside: it will either have no effect on the image, or it will make it better. While the name “sunshade” is generally appropriate, often times it is equally useful, when there isn’t much sun visible at all. Anytime there are bright ligth sources outside the field of view, a sunshade is likely to help.

Keep in mind that stray light can enter the scope through both the objective lens and the eyepiece, and putting a sunshade onto the eyepiece of a weaponsight is not feasible for a number of obvious reasons. However, putting rubber eyeshield on the eyepiece can work for rifles with low recoil or simply when a riflescope is used as an observation device (it also helps in filtering out unwanted light entering your eye). Even something as simple as wearing a baseball hat can help block some unwanted illumination.

As far as scattering goes, there isn’t too much you can do about scattering except take care of the lenses: any dirt or scratches will create some light scatter, so if you want optimal performance, maintain your optics properly. Some scattering occurs simply due to imperfections in the glass, such as tiny air bubbles. However, it is not a major problem in scopes by reputable manufacturers.
Lastly, flare deserves a few words. Flare is a type of stray light that is obviously visible. A lot of stray light simply degrades the image quality without creating any distinctly visible artefacts. Flare is usually easy to detect. The most common type is the veiling flare which, true to the name, looks like a bright curtain across all or part of the image. Veiling flare is usually caused by reflections within the objective lens system (and scopes with large objective lenses are especially prone to it). Other types of flair often show up as bright floating objects within the image and, depending on the type of illumination present, can have a color aspect to them. For example, some halogen light sources produce rather characteristic purple flare in many optics that has very little to do with real life performance, since that kind of lighting scheme is never encountered outdoors.

 

Distortion and Aberration Control
Generally speaking, most issues related to distortion and aberrations in riflescopes are quite overblown, especially in the case of hunting scopes that are not used for extended observation all that much (or at least are not supposed to be used for extended observation). For a riflescope, it is important that whatever is in the center of the field of view is as sharp and clear as possible. The performance at the edges is comparatively less important. Since geometric distortion (itself a type of an aberration) and most other aberration types (with some notable exceptions) are present mostly off-center, they are a secondary concern from a shooter’s perspective.

First of all, what is distortion? Technically, there are quite a few types of distortion in optical instruments, but radial distortion is of most relevance to rifle scopes. Essentially, it describes an instrument’s ability to show you straight lines: if lines that are supposed to be straight, look curved near the edges of the image (and the further from the center, the more curved they appear) you have distortion. There are two types of it: pincushion (lines curve inward) and barrel (lines curve outward). Most types of sporting optics actually build slight amount of pincushion distortion into the image in order to counteract the rolling ball effect when panning. Generally, a lot of variable magnification riflescopes have visible edge distortion at lower magnifications and, by and large, it is not very interesting. We aim with the center portion of the image, so whatever is at the edge is not all that important for as long as it is not strong enough to distract your attention from the point of aim.

As far as optical aberrations go, they can be sub-divided into two types: monochromatic aberrations and color aberrations.

I will not spend a whole lot of time on monochromatic aberrations. They include things like spherical aberration, coma, astigmatism, etc. For the most part these aberrations are a by-product of paraxial approximation in optical design and/or of the fact that most lenses have spherical surfaces. Paraxial approximation simply implies that when the original optical design was done, the designer assumed that the light rays are not going to deviate too much from the optical axis of the scope, and in most cases that holds true. However, some riflescope configurations really push the limits of this approximation, for example compact scopes with large objective lenses.

Spherical lens surfaces have both strengths and weaknesses. Truthfully, they only have one advantage, but it is an important one: they are easy to manufacture very precisely. The main weakness is that the light that goes through the part of the lens that is away from the optical axis is focused at a slightly different spot than the light that is close to the optical axis. Hence, the larger the lens the more apparent this, appropriately named, spherical aberration becomes. Most modern scopes do a very good job of correcting for spherical aberrations, but if you stumble onto a scope with the image near the edges looking a bit out of focus, you are likely looking at some residual uncorrected spherical aberration. A lot of other optical aberrations are also a result of off-axis performance.

By making lens systems a bit more complicated (i.e. by adding appropriately shaped lenses), a lot of the aberrations (including ones I did not mention here) can be corrected, but every extra optical element adds size, weight and cost. It also adds additional surfaces that can cause reflections. Just like everywhere else, there is no free lunch here.

Color aberrations usually stem from the fact that most materials have different indices of refraction at different wavelengths. Refraction is the material property that makes lenses work: when light goes from air into glass, it changes direction a little bit (“bends”, for lack of a better word). How much light changes direction as it enters the glass is determined by the glass’ index of refraction. If we take into consideration primary colors only (blue, green and red), it turns out that for most typical glass, the refractive index for blue light is higher than for green light, which is higher that that for red light. That makes the focal length of the lens slightly shorter for blue light than for green (and red). For similar reasons, the image details of different color can end up reconstructed at different distance from the optical axis. Both of these effects are referred to as Chromatic Aberration (often shortened as CA). The effects of different focal length for different colors are called longitudinal CA, and the color-dependent variations in detail reconstruction around the optical axis are referred to as lateral CA.

In riflescopes, CA is usually an artefact of objective lens system and can be largely corrected with sufficiently sophisticated design. It is also more prominent in higher magnification scopes where the tolerances are generally tighter and various aberrations are more visible. This is where Extra Low Dispersion (ED) glass comes in. When properly used, an addition of an ED glass element can help eliminate any noticeable CA from an optical system. The use of ED glass in riflescopes is not very prominent at the moment, but it is becoming more common. If you happen to need a riflescope with the highest possible magnification, it is worth your while to look at offerings with ED glass in the design.

Both types of chromatic aberration (if visible in your scope) show up as colored fringed at the interface between bright and dark objects within the field of view. The actual color varies depending on the scope design. Red or violet fringes are most common, but I have seen CA of almost every color of the rainbow over the years. Lateral CA, as the name suggests, becomes most pronounced the further you get from the center of the image, while longitudinal CA is visible along the optical axis as well.

My take on Chromatic Aberration in riflescopes, by and large, is the same as that on all aberrations and distortions: I want the center of the image (i.e. the aiming point) to be clear, sharp and as devoid of undesirable artefacts as possible. I am, however, far more forgiving toward edge effects as long as they are not strong enough to be distracting.

 

Tunnel Vision

Tunnel vision is yet another one of those contentious topics where people tend to disagree. Empirically, it seems that some people are bothered by it vastly more than others. My sensitivity to tunnel effect is directly proportional to riflescope price: I am willing to forgive some of it on lower priced scopes, but if I am shelling out some serious money, I get much pickier.

What is tunnel vision? The effect is easier to witness than to describe. An extreme case of tunnel vision is like looking through a straw: the image appears far away from you and it looks narrow. The actual field of view might not be particularly narrow once you look at it carefully, but it looks narrow. This effect is frequently characterized by a thick black ring around the image, although that description is not necessarily accurate. I have seen some scopes with visible black ring around the image that had minimal tunnel effect. In those designs, the eyepiece was overbuilt and had housing so thick that you simply saw the rim of the eyepiece around the image.

Tunnel effect occurs when one of the optical systems inside the scope has field of view wider than the limiting aperture in front of it. The most common occurrence of tunnel effect is due to the relay system seeing the inside of the metal tube that houses the erector lenses. On variable scopes, it is manifested by tunnel vision appearing at lower magnifications. It is not uncommon for a scope to be completely free of tunnel vision for the upper 70% of its magnification range, only to have the effect become progressively worse in the lower 30%. If you notice the black ring around the image become progressively thicker as you dial magnification down, then the relay system is at fault.

The strength of the tunnel effect is determined by the optical design of the riflescope and by how you perceive it. That is one of the reasons you have to get your hands on the scope and look through it. There is nothing in the specifications or anywhere in the accompanying documentation that will tell whether this model has tunnel vision and, if yes, its severity.

 

Exit Pupil and Low Light performance

Determining low light performance of a riflescope is not nearly as simple as some make it out to be. On the other hand, it is not rocket science either. However, there is no substitute to field trial. If you want to be certain how good (or not so good) your scope is in low light, you have to try it out with your own eyes.
Most of the problems in predicting how well a a particular scope performs in light starved conditions naturally stem from differences in individual eyesight. We all see things slightly differently in good light and in poor light these differences often become even more pronounced.
The most obvious (and easy to observe) difference is in the size of your eye pupil. In good light, a human eye pupil contracts considerably, since there is plenty of light available. The amount of light that gets into your eye is directly proportional to the area of your eye pupil, so if during the day, your eye pupil has a typical diameter of ~2mm, its area is ~3.14mm2. As the sun starts setting and there is less light available, a few things happen. First of all, your eye adjusts to the decrease in ambient light and your eye pupil dilates in response. If it increases up to 4mm in diameter, its area becomes ~12.56mm2, or four times larger than it was during the day. So far so good, except the speed and magnitude of eye pupil dilation varies from person to person and is also effected by a number of other factors like dietary habits, age, time of day, etc. For a typical healthy human being under the age of 30, maximum eye pupil diameter is ~7mm when it gets really dark, but I have run into people with 4mm and 9mm maximum eye pupil dilation, so it varies greatly. On top of that, simple things, like how much coffee you have had on that day make a difference.
Aside from the eye pupil changes, the way we process visual information also changes depending on how much light is available. There are two types of light sensitive cells in the eye: rods and cones. Generally, depending on the amount of light available, human eye operates on one of three different vision regimes: scotopic (ultra low light where only the rods collect information), mesopic (low light when both rods and cones collect information) and photopic (good light when the visual information is collected primarily by cones). Even in rather low light hunting, human eye seldom gets into the scotopic mode of operation, usually there is enough illumination for mesopic vision. As a general guideline, as the light gets lower, you know when mesopic vision starts when the colors start changing. When color disappears entirely, you are in the scotopic region.
On top of the other complications, rods and cones are not evenly distributed in the retina. There is a region in the retina that is directly behind the iris called fovea. It is approximately 1mm in diameter and is responsible for most information collected by the eye. The problem is that there are a lot of cones in the fovea, but not a lot of rods. Hence, as the light gets lower and cones stop collecting information, you need to rely on light falling outside the fovea, which is greatly helped by larger exit pupil in your riflescope.
The exit pupil is a function of scope magnification and objective lens. To calculate its diameter, divide the objective lens diameter by the magnification. For example, a 6×42 riflescope has a 7mm exit pupil. A variable magnification 3-9×40 riflescope has ~4.4mm exit pupil at 9x and it gets progressively larger as you lower magnification. In practice, with a 3-9×40 riflescope, you end up with the best low light performance at somewhere between 4x and 7x magnification, depending on how large your eye pupil gets and how low the light is. To know for sure, it is worthwhile to experiment.
Aside from the exit pupil diameter, high image quality really helps. Human brain utilizes the images from both eyes to extract detail, but there is no binocular vision in riflescopes. However, keeping the off-eye slightly open helps. Also, images with higher contrast allow you to maintain some elements of color vision longer. That also helps your brain extract detail out of the picture.
There are a few other things to consider as well. For one, in very low light you actually see a little better with the “corner of your eye”, so to speak. It is also easier to see moving details than stationary ones. In that case, it helps to have the exit pupil of the scope a little larger than your eye pupil. That way your eye can move a little without blacking out the image. Another factor is the change in the F/# of your eye as the pupil dilates. That causes the perceived depth of field of your eye to be quite a bit shallower in low light. Hence, eye distance behind the scope’s eyepiece becomes more critical.  Moreover, in daylight, when cones are responsible for light collection, your eye is most sensitive to green-yellow part of the spectrum.  In low light, as the rods in your eye starts to collect the bulk of the information, eye sensitivity shifts into the green-blue.  That implies that some scopes with anti-reflective coatings well optimized for daylight will not perform all that well after sunset.  On the other hand, a scope that looks decent, but not exceptional during the day, might look better than you thought at night.  Once again, there is no substitute for experimentation.
When all is said and done, keep in mind that for truly good low light performance, you need both high image quality and large exit pupil. If in doubt, err on the side of top notch glass. If the scope delivers just a bit extra light and higher image fidelity to your eye, a moderate exit pupil works surprisingly well in failing light.


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Fellow northern Minnesota hunter here, hunt between Virginia and Ely.  Swamp, woods, clearcuts, no farms, longest shot available now aprox 200 yds.  That will change with the next logging op near camp.

FWIW I have a Red Dot on a .357 S&W, a 1.5x6 on a 6.8 AR,and a 2x7 on my go to rifle, a short barreled .308. I have never felt underscoped.  While I can see where more scope might be wanted to see antlers in shadow across a cut, for where I hunt, more scope isn't as helpful as it is harmful.  Earlier this month I was sitting at one of my longer shot spots watching a lane across a small grass/spruce valley when a pushed smaller buck loped across in front of me at 25 Yds, paused for a moment on the other side of a small spruce like they're apt to do, and then sauntered off.  It would have been difficult to find him quickly that close with a scope set much higher than the 3 or so mine was at. I let him go, didn't see another buck so... took him 3 days later from the same blind at 150 yds plus quartering away w/ the .308, at x7. 

In fixed power for deer a 2.5x would meet my northern Minnesota woods needs better than than a 6x or 10x with a 4x being second choice.  I've seen plenty deer at bow ranges.
In variable, a 2x8 or so would be my next choice in deer-bear-coyote w/ deer rifle scope.

For me, brand is irrelevant as long it's well made, reasonable eye relief, large enough exit pupil, good to very good (doesn't have to be the greatest) glass, and a thick enough duplex to see in the dawns early light. 
  


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/01/2016 at 12:18
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On the number of lenses, here is a snapshot from a Hensoldt manual:


There are 18 lens elements.  Not all are airspaced, so the number of air-to-glass interfaces looks to be around 20, although it is hard to be certain with a such a simplified drawing.

Light transmission through a single such interface is going to vary from 98% to 99.5% depending on the wavelength.  

Here is a plot that shows transmission for single interface and for 20 interface.  Single itnerface plot is based on actual measured data.  This is a pretty decent broadband coating not dissimilar from most mid range scopes and binoculars.  The coatings on the Hensoldt are better than this, but this is still reasonably illustrative.



ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/01/2016 at 16:31
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Thanks, Ilya.

I read that article not long after you you wrote it, and have referred to it since. It was a real eye-opener for me.

"In practice, with a 3-9×40 riflescope, you end up with the best low light performance at somewhere between 4x and 7x magnification, depending on how large your eye pupil gets and how low the light is. To know for sure, it is worthwhile to experiment."

For me, it's about 6.5X for a 40mm objective. I tested a few scopes from 32mm to 50mm objectives, and found I can just set the magnification so the the exit pupil is about 6mm, and the bigger the objective, the longer after dark I can see.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: December/01/2016 at 16:46
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In New York it's illegal to hunt after sunset which is usually 30 minutes before dark. That's for Whitetail.

Coyote hunting is the exception.

We have no Hog hunting here.

We've been known to stretch sunset by 20 minutes or so depending where you might be hunting.😂
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