I am currently considering buying a pair of high quality binoculars and am struggling with the choice between full size (8x42) and compact (8x32) glasses. The full size glasses have an exit pupil of 5 and the compacts have an exit pupil of 4. The full size glasses should pass more light and theoretically have an advantage under low light or twilight conditions.

Unfortunately, the human eye experiences a reduction in exit pupil as it ages, and by 60 or so has an exit pupil of around 4. Thus it seems to me that the benefits of an exit pupil of greater than 4 in a binocular would be lost on someone 60 years or older. The thing that would not be lost on the full size binoculars is the half pound weight penalty over the compacts.

Is the foregoing rationale a valid argument for an older person to select compacts over full size binoculars. Or is my logic flawed? Are there some other characteristics held by full size binoculars that make them preferable to compacts for the older user?

You are right about the exit pupil in oler guys eyes not allowing as much light in as when we were younger, but I think binos should be bought by what we need and want. I have a set of Brunton Eterna 10X50 that have great clarity and brightness but I wish I had a 7X or 8X with maybe 32MM or 36MM lenses as the large binos are heavy and cumbersome to carry.

I fit into that age group and personally I cannot tell the difference between very small changes in light being transmitted through an optical device.

I use a pair of 8x30 binoculars and they are just as bright (to me) as 8x40’s I have looked through.

Consider that the “average†human pupil has a maximum opening of 7mm, and that’s in total darkness. In normal daylight it shrinks down to about 2.5mm, and in bright sunlight it gets even smaller.

That tells me that the “average†human pupil cannot tell the difference between a 4mm and a 5mm exit pupil when it comes to the “extra†light.

For the last few years my primary binoculars have been 8-42 Leu. Pinnacles. They are pretty sharp and not too heavy. I have read that at my age of 67 that I can't use a large exit pupil.

For fun and something to do I put my old Helsoldt 8-56 Nacht Dialyts in the pack and used them and then the 8-42's back and forth all afternoon on a stand. I have had the Dialyts for over 40 years and they are a little big but only 30 oz.

I have read all that stuff E. writes about modern lens coatings etc. As a reference my eye sight is better than average and I don't wear glasses when hunting.

The old Hensoldts have far better resolution than the 8-42 Pinnacles in any light. I could just make out stuff better. I did compare them at very low light and there was not a dramatic difference in so called brightness but there is in resolution. Resolution is what matters.

Actual resolving power will always trump other factors that are at best theoretical. A sharp image with distinct contrast will always appear to be brighter and easier to see, especially in low light when colors start to blend into various shades of grey.

Can resolving power be objectively measured and recorded as a characteristic of a particular glass, or is it a subjective observation that might vary from person to person? Would one expect a larger objective lens to have greater resolving power for any given magnification than a smaller (compact) objective lens.

FWIW, Your actual pupil size might be more than you think, especially if you don't smoke. I'm 45yrs old and had mine measured in low light not darkness when getting ready for Lasix. Mine measured 7.3mm without dialation. YMMV
As far as resolution goes they make several charts with different sizes of parallel lines that can help show the different resolution in various models. Look into dark corners and look for small things in the shadows will also tell you a lot. Imagine you are trying to find a bedded down buck in among the trees and you'll have the basic idea.................DJ

In order to get an “average†you have to have figures on either side of it. Some peoples eyes will be above that average and others will be below it.

I own several 1954 Air Force resolution targets that I use for rifle scopes, spotting scopes and camera lenses. You can set them up at different distances and quickly see what your optics and your particular eyes can distinguish. Again, using the term “averageâ€, the average unaided human eye can resolve about one MOA, or 60 seconds of arc. A scope providing resolving power of 6 seconds of arc (pretty easy to accomplish) at 10x will supply all of the resolving power that the “average†human eye can take advantage of (10 times 6= 60).

Larger objective lenses do contribute to better resolving power, but only when they are accompanied by quality glass and coatings that correct all aberrations. If you had two indentical scopes (except for objective lens size) the one with the larger objective would have better resolving power.

Everyones eyes are different so none of us can say with authority what anothers eyes will or will not perceive. That’s why optometrists have those fancy machines to test each persons eyes!

I’m in my 60’s and wear reading glasses. I can see ants crawling on walls 100 feet away but have trouble with small print up close.

I just completed my own version of Savage99's experiment.

I can see a range of hills about 7 to 10 miles distant from my living room window. Today, being New Years Day, saw a hot air balloon rally along this range of hills. The weather conditions are a bright, sunny, snow covered, winter day on the Canadian prairies. I got out a pair of Bushnell 7x24 compacts and a pair of Karl Wetzlar 7x35 full size binoculars.

The image through the Karl Wetzlar 7x35s was brighter and clearer than through the Bushnell 7x24s. The difference was subtle but noticeable. Even more interestingly, my wife, whose distance vision is poor, found the difference between the Wetzlars and the Bushnell's dramatic. She was unable to discern colours in the Bushnells, but could through the Wetzlars.

I realize there are two factors to consider here; increased objective lens size and lens quality. However, I am leaning towards three conclusions:

1. A larger objective lens improves performance (resolution?)

2. Higher quality glass improves performance (assuming Wetzlar lenses are higher quality than Bushnell lenses)

3. Incremental performance improvements are increasingly important as normal eyesight deteriorates (age related or otherwise)

Thanks for your comments so far and please continue to contribute.

An informed consumer usually makes better choices!

One thing I can guarantee you is that images viewed through higher quality optics with smaller objective lenses will appear “brighter†than those viewed through lower quality optics with larger objectives. Bushnell optics are not in the same ball park with the better brands when it comes to quality of glass and coatings used to remove aberrations. I would bet that your 7x35 Wetzlar binoculars would also appear much brighter than a 7x40 pair of Bushnells.

WoolyESS--You are correct that pupils get smaller as we age. Go into a dark theater with a youngster and they will be spotting their friends when we are still trying to see the floor. I am 63 now and before I was 30,I bought a pair of American made(Rochester,NY) Bausch&Lomb 7x35's(still have them and after all the use as good as new). Recently I bought a few more pairs to include 6x-30 and 7x50. The 6x-30 and 7x-35 both have 5mm exit. Side by side with the 7x-50's which have a 7.143mm exit---I cant tell a drop of difference. Luckyducker-you mention the heavy bulky binos. Have you tried the shoulder straps? I have found getting the weight off my neck and the shoulder type holds them close to your body makes them "must have" equipment for me. Even with smaller binocs I wont be without the shoulder strap.

When hunting I carry Nikon Travelite IV 8x25 binocs in my pocket.

These are not the binocs you want looking for game from the car, where weight doesn't count.

Wooly,

Your initial assumption that it is meaningless to have an exit pupil greater than the diameter of your eye pupil is correct. The first issue is to find out what your personal eye is capable of. As a life-long non-smoker who has less difficulty in the dark than most, I have to assume that my pupil dialation potential is still pretty good at age 56. On the other hand, the difference I see in a 4mm and 5mm exit pupil is negilgible, and certainly less than the difference created by higher and lower quality lenses, prisms, and coatings.

Apples-to-oranges comparisons of different makes of binoculars tells you nothing about what a smaller or larger objective lens is doing for you. The size of the objective has no impact on resolving abililty of the binocular once maximum usable exit pupil has been achieved.

Back to your original question -- should you get the 32mm's which are handier, or the 42mm's which give you a larger exit pupil for dim-light performance? Well, that's like asking what's the best gun to use when you see a trophy 12-point buck. Answer: The one you're holding in your hands. That's my way of saying that the smaller, lighter, more compact instrument is more likely to be where you want it when you want it. Does an extra two or three minutes of better resolution after dusk (and well after legal shooting hours) justify hauling around the extra weight and bulk of the larger instrument? In my view, it's the other 99.8% of the day that is more important.

quote:

Originally posted by Stonecreek:
Wooly,

Your initial assumption that it is meaningless to have an exit pupil greater than the diameter of your eye pupil is correct.

I would respectfully disagree. There is a reason that Marine Binoculars are typically 7x50 or a combination that leaves a particularly large exit pupil and it's not for night use. Having the oversize exit pupil makes for a pair of binoculars that is more forgiving of motion and shakes. They can move in your hands more without your pupil leaving the light cone coming from the binoculars.
It's correct that it may not make them brighter but there are other factors...............DJ

Larger exit pupils on rifle scopes can be somewhat advantageous since it allows you more latitude in head/eye placement behind the scope, but with binoculars that really isn’t an issue.

No sense in paying for something, or packing around more weight, if your eyes can’t take advantage of what the cost and weight are giving you.

quote:

Originally posted by fyj:
Larger exit pupils on rifle scopes can be somewhat advantageous since it allows you more latitude in head/eye placement behind the scope, but with binoculars that really isn’t an issue.

No sense in paying for something, or packing around more weight, if your eyes can’t take advantage of what the cost and weight are giving you.

Before you take that as a given you might try holding a pair of 10x32's for about 30 minutes and then try out a pair of 10x50's for about the same time and see which is easier to hold steady and use.
It's also easier to make larger lenses to a higher resolution than smaller ones, whether it's worth the extra cost and weight for the extra resolution gained is another question......................DJ

quote:

Originally posted by djpaintles:

quote:

Originally posted by Stonecreek:
Wooly,

Your initial assumption that it is meaningless to have an exit pupil greater than the diameter of your eye pupil is correct.

I would respectfully disagree. There is a reason that Marine Binoculars are typically 7x50 or a combination that leaves a particularly large exit pupil and it's not for night use. Having the oversize exit pupil makes for a pair of binoculars that is more forgiving of motion and shakes. They can move in your hands more without your pupil leaving the light cone coming from the binoculars.
It's correct that it may not make them brighter but there are other factors...............DJ

My comment was in regard to "resolving power", not other aspects of utility. It is true that the larger exit pupil allows less precise placement of the binocular in relation to the eye, but I also agree with FJY that this is not much an issue with binoculars as compared to rifle scopes. I still feel that the overall size, weight, and bulk of the binocular is a more practical consideration.

quote:

Originally posted by djpaintles:

quote:

Originally posted by fyj:
Larger exit pupils on rifle scopes can be somewhat advantageous since it allows you more latitude in head/eye placement behind the scope, but with binoculars that really isn’t an issue.

No sense in paying for something, or packing around more weight, if your eyes can’t take advantage of what the cost and weight are giving you.

Before you take that as a given you might try holding a pair of 10x32's for about 30 minutes and then try out a pair of 10x50's for about the same time and see which is easier to hold steady and use.
It's also easier to make larger lenses to a higher resolution than smaller ones, whether it's worth the extra cost and weight for the extra resolution gained is another question......................DJ

I wouldn’t know about the first because I don’t use binoculars over 8x. But I have used 7x50’s for VERY long periods of time and find them less “comfortable†than my tried and true 8x30’s.

As to the other statement, I’m am unaware of any optical law or manufacturing process that would support such a theory.

My only point was that optical devices have many features that may or may not have any practical or noticeable value to certain people‘s eyes, so it’s best to try them out to see what you see.

I'm 62. I also own and use binoculars in the 8X32 and 8X42 sizes.
First of all, people do vary as to how much night vision, if any, they have as they get older. Some become night blind, their pupils won't open much past 2mm. These are the people who can't drive at night. I'm at the other end of the scale, my night vision works fine. I had a full eye test when I was 55.
Actually there is a difference in resolving power between binoculars of the the same make and model but with different exit pupil sizes. The one with the larger exit pupil does better. Even extra magnification doesn't off set this. A 10X42 Zeiss FL is just a tiny bit less sharp than an 8X42 FL. But you have to stack them and work pretty hard to see it.
On a partical level, I find my 8X32 Nikon LX-L's to be quite different when used in the field than my heavier 8X42 Leica BA's. The Nikon is much lighter by 10 ozs. That means I can comfortably carry it on a short strap around my neck all day. The heavier Leica I find I need to hang cross body over my left side to be comfortable all day.
There is an apparent difference when using them as well. The lighter Nikons have noticably more image shake than the heavier 8X42. This becomes readily apparent if you use them while standing. Makes it harder to see really fine details.
When rested, by the way, and stacked, they are both equally sharp.
So, if I going to cover lots of ground, do alot of climbing, etc., I tend to favor the 8X32. If I'm still hunting and looking through cover alot, I go for the 8X42. The 8X42 does have better low light performance. But that depends on what kind of day it is and what kind of cover I'm in. In an open area, on a bright, clear day, especially if the moon is up, the 8X32 works fine during legal shooting hours. But, if the day has full cloud cover, and I'm in dark timber, the 8X42's are needed to last to the end of legal shooting hours. E