Buckfever:
This is an excellent question. Let's assume that you have spent more than about $300 for your binocular. Your optics should probably be as good as any. My experience is that investing large numbers of dollars for best-quality binocular insures durability -- barrels' alignment, water resistance, warranty, scratch resistant lenses, roof prisms -- rather than lens quality.
You have two contrary factors (NOT contradictory) to consider: twilight factor; and exit pupil diameter. Without investing pages of text, twilight factor weights magnification -- the higher the magnification, the better you can view something regardless of how much available light there is. Exit pupil diameter weights the ratio of ocular lens to objective lens -- the higher the [ratio] number the more available light reaches your eye.
You have butted against one of the kickers. If the exit pupil diameter is too small, you cannot see your target well in low light. And it won't matter how good your optics are.
The other kicker is that the human eye's pupil has a maximum dilation of about 5 mm. As you age, this number drops to about 3.75 mm after you're 40-some-odd.
And when you use a binocular having large (40+ mm) objective lens with 7 or 8 powers of magnification, the binocular tends to be BIG and usually HEAVY. Investing more money to buy roof prism binocular tends to reduce the bulk and weight. It also reduces the stereoptic effect of the binocular barrels. Your depth of view is less.
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Having wasted thousands upon thousands of dollars buying best-quality binoculars that fuctioned perfectly but were unsatisfactory on hunting trips, I have the perfect solution to YOUR PROBLEM from my point of view.
I use Zeiss 8x30 B/GA IF Olive binocular with F2 range finder in right barrel; objective and ocular lens covers; and Zeiss snow filters. Total weight is less than 25 ounces. Notice the exit pupil is 3.75 mm.
This is not the smallest or lightest or the easiest to use binocular. They were first manufactured in 1964 for NATO service, then became commercially available. They have individually focusing eye pieces -- more durable than center focusing but slower. This is not a problem if you think about what distances you intend using your binocular.
Other binoculars I have used that were nearly as effective include: Leitz Trinovid 6x24s, in the Midwest; Leitz Trinovid 7x35s.
The reason I always buy a best-quality binocular is that when you're out in the field, having a back-up binocular in camp is useless. You invest nearly all your time (Rocky Mountain and Cascades Mountains west) looking through your binocular. All this time your binocular is the most important tool you have. If it fails, you're through.
My experience is that binoculars using Schott optical glass are more scratch resistant than others. Schott is a German company. Zeiss, Leica, and some other European manufacturers use Schott glass.
Japanese manufacturers do not use Schott glass. The quality of the glass and grind appears to be excellent in best-quality binoculars -- comparable to best-quality European binoculars.
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I would never consider anything made in Red China. Not only will it be made for a budget, I refuse to buy from a place that uses slave labor, where no technician in this country would want to work. I'll back my prejudice with the few extra dollars difference.
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Differences I think I detect become noticeable after several years of use. And please note that I cannot confirm this difference via rigorous testing. This is anecdotal -- my experience plus perhaps three dozen others over the past 15 years.
Were I on a budget, I would look at porro prism binoculars before roof prisms. I would also look at recent military surplus binoculars. 8x30s made, say, after 1985 might be an excellent solution.
One final thing, Zeiss discontinued distribution my binocular in 2001, I believe. They are available only in Europe now.
Hope this helps.
