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Low Light Performance

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/27/2005 at 08:26
Rusty View Drop Down
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WHat are the optical qualities that enhance low light performance?  It seems that too much brightness could work against low light performance, as it may wash out some objects with their apparent brightness.  The other qualities: resolution, contrast, and color bias (from the multi coating layers), may have more importance in the low light performance of optics in low light.  Does anyone have any input on this pressing issue (at least for me it is an important quality)?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/13/2005 at 17:22
lucznik View Drop Down
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I suppose the thing that you need to understand first and foremost is that no binocular actually gathers light at all.  In other words a binocular (with the exception of night vision optics which are a totally seperate topic altogether) cannot make any image brighter than it appears under ambient conditions (i.e. to the naked eye.)  Any claim to the contrary is a manufacturer's marketing gimmick.  No binocular can, by virtue of its "brightness," can cause an image that was otherwise clear to appear washed out.
 
What you are then looking for is a binocular that allows for the highest percentage of light to make it to your eye. Each time light hits one of the glass, prism, mirror, etc. surfaces a portion of that light is "lost."  This means that it is reflected off in a direction that is unusable to your eyes. The various coatings that manufacturers put on their optics are designed to limit how much of this light is reflected away.  To this same end is the eternal quest for better quality, defect free glass.
 
For optimum performance in a binocular you want to ensure that it uses BAK 4 prisms, that are fully multicoated.  You also (in a roof prism) want your lenses to be Phase Correction coated.  Additionally you should understand that not every optics company's "full multicoating" is of the same quality as everyone elses'. No Tasco binocular is ever going to come anywhere close to comparing with a Swarovski, Zeiss, Leica, etc for "brightness." This is also true with phase correction coatings. The higher you go in price the better glass you get.  You also get better, more, and more precise coatings and higher levels of quality control.  All of these things can and will affect low light performance.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/14/2005 at 08:45
Rusty View Drop Down
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Here is a link to a discussion on this topic in a birdforum:  http://www.birdforum.net/showthread.php?t=37439

 

 

Basically, forget about all the reviews and just test drive some premium binos and pick one that works well for your needs. 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/02/2005 at 09:45
gremlin View Drop Down
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To keep it in simple terms--size of objective lens matters most, quality and quantity of coatings matters second, quality of construction matters third, and eye alignment matters fourth in my personal experience with low light applications.

 

No 8x20 compact made (Swarovski notwithstanding) will be as bright as a $75 7x50 Olympus Pathfinder nor will it align with your eye nearly as quickly nor stay aligned for as long a period of time.

 

The question is will you want to carry the Pathfinders around with you given their bulk and weight?

 

Between comparable size binoculars, quality and quantity of coatings makes a bigger difference to my eye than prism difference--Bk7 vs Bak4 seems to matter less in low light than Full Muli-coating from a big manufacturer.  If you read some of the star gazer sites, some of them actually prefer Bk7 for their applications for a number of reasons.  My 6x32 Leupold Katmai with Bk7 prisms far outperform my 10x42 Bausch & Lomb Bak4 prism Hemispheres due to better quality coatings.

 

If the objective sizes and coatings are similar, then the quality of construction really begins to come into play and here's where the Swarovskis, Leicas, Zeiss, high end Nikon, etc. pound their competition.  Their construction standards force their manufacturing plants to supply a binocular that will hold it's alignment better under harsher conditions over longer periods of time.  The internal blackening and baffling will prevent stray light from diminishing the quality of the image.  You can't beat the expensive binoculars when it comes to providing a beautiful, satisfying image for decades of use and this is especially apparent when it comes to low light situations.  They minimize stray light and maximize the light from your objective image that is going to get to your eye so that your brain becomes the deciding factor, not the particular optical instrument you're holding.

 

The fourth major consideration is eye alignment--better eye relief yields a faster low light picture.  Period.  How long does the average bird, doe, squirrel, etc. ever remain in one place?  The faster you can align your eye to the picture before you, the quicker your pupil can adjust it's own internal aperture to the amount of light it's given.  If it takes too long to line your eye up correctly with the center of the optical instrument you're using, the subject's probably already moved.  It doesn't matter how good your coatings are if the time it takes to align your eye is measured in full seconds rather than tenths of a second.  You're not gonna spot your prey.

 

Just my two cents, but I hope that helps...

 

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

Take the long way home

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/19/2016 at 09:33
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Rusty:
You have it right - " The other qualities: resolution, contrast, and color bias (from the multi coating layers), may have more importance in the low light performance of optics in low light." don't know why everyone focuses on transmission.

The idea is to get maximum visual information. Magnification is also an important factor and so is reducing, as much as possible, the ambient light impacting your eye (eyes) from around the eyepiece.
This can be done using the various soft rubber eye cups available. This alone can make a huge difference!

To help think of the subject more clearly, just take each optical quality to absurdity. For instance, if colors are skewed (biased) far enough it becomes obvious that ultimately no colors can be separated.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/19/2016 at 10:04
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This thread is 11 years old.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/19/2016 at 12:13
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Yet it remains among the most asked questions regarding hunting scopes.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/19/2016 at 12:26
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That is true.

Still, Rusty has not visited the forrum since 2007.

ILya
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