New Posts New Posts RSS Feed - is chromatic aberration a function of cost?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Check GunBroker.com for SWFA's No Reserve and No Minimum bid firearm auctions.

is chromatic aberration a function of cost?

 Post Reply Post Reply   Topic Search Topic Search  Topic Options Topic Options
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/22/2010 at 17:06
onfinal View Drop Down
Optics Apprentice
Optics Apprentice


Joined: April/28/2009
Status: Offline
Points: 135
I just bought a Vortex Skyline 20-60x80 non-ED spotter.  Went to the 200 yard range today, sun was in and out so not overly bright, and the chromatic aberration on my Champion VisiShot target was pretty severe. Is c/a a function of the cost ($450 in this case)?  Would it be less or non-existent in a more expensive spotter?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/22/2010 at 17:12
RifleDude View Drop Down
MODERATOR
MODERATOR
Avatar

Joined: October/13/2006
Location: Texas
Status: Offline
Points: 14310
Yes.

CA is reduced or eliminated with the use of "HD/ED/FL/APO" glass in the objective lenses, which consists of either extra dense, extra low dispersion glass or fluorite lens elements.  This option doesn't come cheap.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/22/2010 at 20:23
onfinal View Drop Down
Optics Apprentice
Optics Apprentice


Joined: April/28/2009
Status: Offline
Points: 135
RD, thanks.  Not exactly what I wanted to hear but helpful, and leads to a couple more questions:

1.  On average, how expensive do I have to go for an 80mm objective that has little or no CA?

2.  I'm thinking seriously of returning this Vortex Skyline if the seller will take it.  But before I do I want to make sure I have done everything I can to make it work as well as possible.  Is there anything I can do to lessen the CA -- sunshade(s), aiming direction re: sun, time of day, etc. -- or is it always going to be there no matter what in this level scope?

I really appreciate your help with this.  I thought I had researched it pretty well, but obviously not.

onfinal
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/22/2010 at 20:54
tpcollins View Drop Down
Optics Journeyman
Optics Journeyman


Joined: January/12/2009
Status: Offline
Points: 325
Both my Stokes Sandpiper and Bushnell Excursion each had some abberation around the outer edges but it was not as much an issue of degrading the overall view as it was a nusiance and just knowing it was there. 
 
However, my Leupold Gold Ring FLP has no abberation whatsoever - so I assume it does cost money to eliminate abberation.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/23/2010 at 21:21
Huck BB62 View Drop Down
Optics GrassHopper
Optics GrassHopper
Avatar

Joined: February/20/2010
Location: Alaska
Status: Offline
Points: 18
Well, at least it's not brand limited! I bought a non HD Swarovski last week and took it back because of this. The HD version is, well, awesome. 

The Bushnell Excursion FLP 80 that I tried did have some, but not much. I'd consider it a BARGAIN at what they charge for it. If I could've digiscoped with it, I'd have bought it because it's a third the price of my Swarovski!  Is my Swarovski three times as good as the Bushnell? Not even close, but that's the exponential cost rule of optics. One thing that bugged me about the Bushnell is made by the chicoms. That too has a large part to play with how I spend my money.

No sunshade or adjustments will cure the CA. I wish it would. 

Let us know how it turns out.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/23/2010 at 22:46
onfinal View Drop Down
Optics Apprentice
Optics Apprentice


Joined: April/28/2009
Status: Offline
Points: 135
I bought the Bushnell Excursion FLP 80 and returned it because a) it was Chicom, and b) its weight was misrepresented; it was almost 4.5 lbs. out of the box and way too heavy to be carrying very far.

I bought the Vortex Skyline 20-60x80, at ~ $5o more than the Bushnell, because of the high praise for Vortex products I have seen here and elsewhere.  But turns out it too is Chicom, and although considerably lighter than the Bushnell, really comes on strong with the CA.  I didn't have the Bushnell long enough to give it a field test, so I can't compare CA between the two scopes.

I am fast reaching a point of no return here.  Don't really want to go 700-1000$ or more for a spotter I use infrequently, but OTOH have no use for my $400+ doorstop either.  I may just give up and walk down to check my targets at the 220 yard range.  I need the exercise anyway.

Thanks for the comments.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/23/2010 at 22:56
RifleDude View Drop Down
MODERATOR
MODERATOR
Avatar

Joined: October/13/2006
Location: Texas
Status: Offline
Points: 14310
Originally posted by onfinal onfinal wrote:

RD, thanks.  Not exactly what I wanted to hear but helpful, and leads to a couple more questions:

1.  On average, how expensive do I have to go for an 80mm objective that has little or no CA?

2.  I'm thinking seriously of returning this Vortex Skyline if the seller will take it.  But before I do I want to make sure I have done everything I can to make it work as well as possible.  Is there anything I can do to lessen the CA -- sunshade(s), aiming direction re: sun, time of day, etc. -- or is it always going to be there no matter what in this level scope?

I really appreciate your help with this.  I thought I had researched it pretty well, but obviously not.

onfinal


1.  I don't know on average, but I'm not aware of any really good 80mm scopes with little to no CA for less than $1150 - this being the Pentax 80 ED.
2.  There is nothing you can do; it will always be there.  It is amplified when looking at objects against highly contrasting backgrounds, i.e. objects against a bright sky, etc.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 00:08
Huck BB62 View Drop Down
Optics GrassHopper
Optics GrassHopper
Avatar

Joined: February/20/2010
Location: Alaska
Status: Offline
Points: 18
Well, it hurts the wallet to buy truly great optics. But, it's very satisfying. Of my core toys, my great optics are my most treasured. Also, they're like cash, really. You won't get 100% return, but it's wayyyyy up there on value retention compared to any other consumer good. You'll appreciate good optics every single time you use them, as long as you own them. 

I'd buy a cheaper rifle before I bought cheap optics. 

I haven't used that Pentax but on the tests, birder forums, and as evidenced here, I'd say it's a bargain comparatively. It also has the fantastic benefit of using traditional 1.25" eyepieces. This is a real boon because there are great eyepieces for a really reasonable price for that use. 

I guess optics is truly one of those things where you're truly going to get what you pay for.  

I'm surprised that the Vortex is chicom given their marketing. I'm sorry to hear that. Some Japanese branded optics are chicom also. It's always worth the look.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 09:05
RifleDude View Drop Down
MODERATOR
MODERATOR
Avatar

Joined: October/13/2006
Location: Texas
Status: Offline
Points: 14310
Originally posted by Huck BB62 Huck BB62 wrote:



I'm surprised that the Vortex is chicom given their marketing. I'm sorry to hear that. Some Japanese branded optics are chicom also. It's always worth the look.


If you are referring to the Vortex Razor HD spotter, it is NOT Chicom; it is made in Japan.  The only Chinese made optics from Vortex are their low end products.  ALL of their top of the line optics are made in Japan, and their second tier stuff is made in the Philippines.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 09:47
Rancid Coolaid View Drop Down
Optics Jedi Master
Optics Jedi Master
Avatar

Joined: January/19/2005
Location: United States
Status: Online
Points: 7692
I have the Pentax and like it very, very much, money very well spent. I've compared it to much, much more expensive scopes - some are a little better, none are dramatically better.

You will be spending more than $1000 to get rid of the CA, that's how it is. 


Edited by Rancid Coolaid - February/24/2010 at 09:47
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 10:35
onfinal View Drop Down
Optics Apprentice
Optics Apprentice


Joined: April/28/2009
Status: Offline
Points: 135
Thanks for all the comments....lesson learned.  There's no such thing as too much research for truly good optics.

Just to keep the record straight, I'm talking about a Vortex Skyline 80 here, not a Razor HD.  The Chicom part is my own fault for not checking it more carefully.  I thought Vortex name plus three times what the "cheapies" cost, it's got to be good, right?  My mistake.  It will be going back, and the search continues.


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 10:57
Rancid Coolaid View Drop Down
Optics Jedi Master
Optics Jedi Master
Avatar

Joined: January/19/2005
Location: United States
Status: Online
Points: 7692
No mistake, just understand, you get what you pay for.

If someone made a $500 spotter that competed well with the $3000 German spotters, that'd be too easy.  Life ain't ever that easy!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 11:36
Scott_at_Vortex View Drop Down
Optics Apprentice
Optics Apprentice


Joined: February/18/2010
Location: Middleton,WI
Status: Offline
Points: 103
Originally posted by onfinal onfinal wrote:

Thanks for all the comments....lesson learned.  There's no such thing as too much research for truly good optics.

Just to keep the record straight, I'm talking about a Vortex Skyline 80 here, not a Razor HD.  The Chicom part is my own fault for not checking it more carefully.  I thought Vortex name plus three times what the "cheapies" cost, it's got to be good, right?  My mistake.  It will be going back, and the search continues.


I am sorry to hear that you are not happy with it. Contact us as soon as you can and we will do whatever we need to do to make you happy.
 
Scott
1-800-426-0048  ext 323
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 11:36
JGRaider View Drop Down
Optics Master
Optics Master


Joined: February/06/2008
Status: Offline
Points: 1431
Originally posted by Rancid Coolaid Rancid Coolaid wrote:

No mistake, just understand, you get what you pay for.

If someone made a $500 spotter that competed well with the $3000 German spotters, that'd be too easy.  Life ain't ever that easy!


You're right about that Rancid, although I feel the euro alpha stuff is grossly overpriced.  That includes spotters, binos, and premium scopes. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 11:37
SVT_Tactical View Drop Down
Optics Retard
Optics Retard
Avatar
Chief Sackscratch

Joined: December/17/2009
Location: NorthCackalacky
Status: Offline
Points: 28753
Gotta love venders who support the OT.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 11:43
Rancid Coolaid View Drop Down
Optics Jedi Master
Optics Jedi Master
Avatar

Joined: January/19/2005
Location: United States
Status: Online
Points: 7692
Everything is a trade-off: spend less, give up some resolution and clarity.

"Grossly over priced" is a subjective term, I run a Pentax 80 ED spotter next to a Hensoldt 3-12x56 scope, the spotter does what it needs to do so the rifle scope can do what it needs to do. 

Everything is a trade-off.


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 11:51
lucznik View Drop Down
Optics Master
Optics Master


Joined: November/27/2004
Location: United States
Status: Offline
Points: 1436
Originally posted by tpcollins tpcollins wrote:

my Leupold Gold Ring FLP has no abberation whatsoever - so I assume it does cost money to eliminate abberation.  


Your assumption is correct, though not necessarily for the reason you have stated.  One of the primary reasons why the FLP-type scopes will show little-to-no CA is due to the use of mirrors rather than prisms in their design. This is also true of CAT scopes.

 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 12:03
JGRaider View Drop Down
Optics Master
Optics Master


Joined: February/06/2008
Status: Offline
Points: 1431
Originally posted by Rancid Coolaid Rancid Coolaid wrote:

Everything is a trade-off: spend less, give up some resolution and clarity.

"Grossly over priced" is a subjective term, I run a Pentax 80 ED spotter next to a Hensoldt 3-12x56 scope, the spotter does what it needs to do so the rifle scope can do what it needs to do. 

Everything is a trade-off.




For the most part the trade off you describe is true.  However when I compared my Nikon 82ED to my neighbor's Zeiss 85 Fl T there was no difference optically.  Several aoudad and mule deer hunts with him have only reinforced our findings.  In fact, the Nikon is usable under the right conditions at 75x, and the Zeiss obviously cannot do that.   The Fieldscope for $1100, or the Zeiss for $2000? 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 12:30
Rancid Coolaid View Drop Down
Optics Jedi Master
Optics Jedi Master
Avatar

Joined: January/19/2005
Location: United States
Status: Online
Points: 7692
Everyone's eye differ.  And experiences.

I don't buy big-names for the name, I buy what I buy for the product and the task at hand.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2010 at 21:20
Huck BB62 View Drop Down
Optics GrassHopper
Optics GrassHopper
Avatar

Joined: February/20/2010
Location: Alaska
Status: Offline
Points: 18
I unfortunately did not get to try the Vortex. I'd like to have, but got a good deal on my Swarovski. I wanted top notch, period. Counting brow tines and other crucial activities with a scope are what it's all about. After I've dedicated who knows how much money and time on an expensive hunt, great optics just don't seem so expensive. 

If you can get a Nikon Fieldscope for $1100 or a Zeiss for $2000, that's a heck of a deal, neither one of those fine scopes should be a disappointment!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/25/2010 at 11:40
onfinal View Drop Down
Optics Apprentice
Optics Apprentice


Joined: April/28/2009
Status: Offline
Points: 135
Originally posted by Scott_at_Vortex Scott_at_Vortex wrote:

Originally posted by onfinal onfinal wrote:

Thanks for all the comments....lesson learned.  There's no such thing as too much research for truly good optics.

Just to keep the record straight, I'm talking about a Vortex Skyline 80 here, not a Razor HD.  The Chicom part is my own fault for not checking it more carefully.  I thought Vortex name plus three times what the "cheapies" cost, it's got to be good, right?  My mistake.  It will be going back, and the search continues.


I am sorry to hear that you are not happy with it. Contact us as soon as you can and we will do whatever we need to do to make you happy.
 
Scott
1-800-426-0048  ext 323


UPDATE!

I called Vortex this morning and received an immediate call back from Corey in c/s.  Had a long and informative conversation about chromatic aberration in non-ED scopes, the gist of which was very much like the responses I got here on OT: I need better glass to lessen the CA.

Vortex is sending me a used/return/demo ED Skyline 80 for trial to see if the ED glass lessens the CA problems of my non-ED model.  I can't ask for any more than that.  When I get it and try it out, I'll report back.  I'm hoping for significant improvement in the CA department . 

In the meantime, kudos to Scott and Corey and Vortex for going all out to help.  Seems their system doesn't like Comcast and, wouldn't you know, Comcast is my ISP.  This probably explains my original email to them dropping out.  If you are a Comcast customer and need to contact Vortex, pick up the phone and call their 800 number.  They want to help.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/25/2010 at 15:17
Bird Watcher View Drop Down
Optics Master
Optics Master
Avatar

Joined: August/30/2006
Status: Offline
Points: 1490
Originally posted by onfinal onfinal wrote:

 There's no such thing as too much research for truly good optics.
 
Chromatic Aberration, Triplets, Semi-Apo, Apo [Re: EdZ]
      #662278 - Sat Oct 29 2005 11:41 AM
Edit post Edit   Reply to this post Reply   Reply to this post Quote Quick Reply: Quick Reply  
CHROMATIC ABERRATION (CA)

The most important thing the user should understand is that it is impossible to completely eliminate CA from a lens system. It can be reduced to an almost imperceptible level, but cannot be eliminated altogether.

This is an explanation of what chromatic aberration is and how it affects the overall image
Chromatic Aberration

This explains some of the math of CA
Chromatic Aberration on planetary disks

Chromatic Abberation is one of the least worrisome aberrations. In an astro binocular, it is only present in about 1% of the objects viewed. So it should be one of the least critical aberrations on which to base a decision. Judge your choice of binocular on all the features and known aberrations that make a difference in the view 99% of the time. Honestly, the planets are not binocular targets, so the moon is the only astro target that would be a consideration for judging whether one needs to consider CA in the choices of astro binocular.

For terrestrial viewing CA becomes an important factor. CA becomes a problem in extremely bright conditions, not in low light conditions. However, there are not too many people using 15x or 16x binoculars for terra viewing.

A Table Plotting Chromatic Aberration vs Objective Size and Focal Length
see this interesting post in the refractors forum that discusses CA.. From the post...
" It illustrates the relationship of aperture and f/ratio to displayed chromatic aberration in achromatic refractors. Roughly, telescopes with similar CA ratios can be expected to display similar levels of visual CA; as CA in achromatic systems is a function of objective diameter and focal ratio.

Using this chart, one can get an idea of how another refractor will perform based on the performance of whatever model one already has. "


See this thread for
A discussion of CA in premium and well corrected optics


A discussion related to chromatic aberration in several model binoculars took place embedded in this thread.
Obie vs Fujinon CA



-------------------------------------------------------------------------------

There are two different forms of CA

Logitudinal CA is caused by the fact that, even with precisely on-axis light, in the focused image from an achromat all the wavelengths do not have the same focal length. Typically light in the image of an achromat varies from blue to red focal length by 1/1800th to 1/2000th of the focal length of the objective lens. So, for a f/4 100mm binocular, the focal length of red to blue might vary by as little as 0.2mm. That may seem inconsequential to you, but that might represent a 15°-20° turn of a center focus dial on a binocular.

Light that is not focused precisely does not make the minimum sized point of light in the image. If the minimum diameter circles of light for each wavelength is at a slightly different focal length, that means when focused precisely at any one color (usually yellow) that the Airy disks of all other wavelengths (colors) have slightly larger sizes and they overlap the yellow image, forming CA in the on-axis image. This is not generally seen by the observer unless you slightly defocus the image. But rest assured it is there and it has an affect on contrast of fine detail. This may possibly be seen in the inability to bring the focus to a precisely small point of light. An achromat that is not corrected to even 1/1800th f may have a difficult time forming a precisely small image of even a moderately bright point source.


Lateral CA is caused by the fact that the light rays forming the image across the lens all have slightly different lengths to a focal plane but the focus mechanism wants to focus across a flat plane. For all the points of light in an image to be in focus at exactly the same time, our focus mechanism would be required to focus across a slightly curved image plane. That doesn't happen. Since the system is incapable of providing that precision, we see the light spread across that plane at varying amounts of out-of-focus.

If you were to draw several half inch wide concentric circles over the field of view, you would see that in the outer fov ring you see all one color, green, in the next ring in all another color, purple. The color you see is dependant on how far off-axis the image is in the plane. The further off axis, the longer the physical length of the light ray beam to the plane. The varying lengths of light rays causes each color to be out of focus more-so than some other color at different distances off axis. This form of CA is entirely due to where the light falls across the plane.

See this thread Question about CA....


----------------------------------
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/26/2010 at 11:03
anweis View Drop Down
Optics Professional
Optics Professional


Joined: January/29/2006
Status: Offline
Points: 971
Originally posted by onfinal onfinal wrote:



1.  On average, how expensive do I have to go for an 80mm objective that has little or no CA?
Not too much more that that Skyline.
Celestron Regal 65 F-ED is probably the best scope dollar for dollar these days.  There are also a Regal 80 F-ED and 100 F-ED if you insist.
 
I have used the Skyline for one day and it ruined my fun. Next to it, my Nikon 50 ED was super extra premium deluxe.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/26/2010 at 15:19
koshkin View Drop Down
MODERATOR
MODERATOR
Avatar
Dark Lord of Optics

Joined: June/15/2004
Location: United States
Status: Offline
Points: 10961
Generally speaking, CA is most difficult to control in spotters that are short, but have large objective lenses.  The longer the spotter for a given objective size, the easier is CA to control.  That is one of the reasons why you often have less prominent CA in FLP designs even when they use comparatively unsophisticated objective lens systems.

Ultimately, if you want an image with very little noticeable chromatic aberration, be prepared to pay for ED glass and a fairly sophisticated design.  Presence of ED glass by itself does not guarantee CA-free image.  Here are some general recommendations on spotters in varying price ranges:

ILya
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Similar Threads: "is chromatic aberration a function of cost?"
Subject Author Forum Replies Last Post
Scope cost vs. Gun cost tjones96761 Rifle Scopes 43
Vortex Razor - excessive chromatic aberration? nodule Binoculars 117
Multi-function tripod ND2000 Spotting Scopes 3 9/19/2007 1:52:25 PM
so who has scopes costing more than your gun outlawskinnyd Rifle Scopes 29
Can (or does) chromatic aberration cause misses? MZ5 Rifle Scopes 3
Reloading equipment & other related cost EAGLE Reloading & Ballistics 19
Please recomend a low cost scope for 17hmr BobC Rifle Scopes 6
Why the huge cost diff in Picatinny Rail offerings REP Rings and bases 18
COST - Fixed vs. Variable TruthNtime Rifle Scopes 10
Cost of hunting 8shots General Hunting 33 8/27/2007 3:47:11 AM


This page was generated in 0.219 seconds.