Read this over on Archerytalk a few years ago. Pretty interesting. For bowhunting I like an 8x42 but I do like more power for glassing from the truck. Regardless of being able to hold it steady there's times where more magnification is nice. I've got a pair of Vortex 15×56 for the truck. I can definitely bring them in close but I have to rest them on my window to keep it steady.
"Ok....I purposely didn't mention anything in my original post about the size of the objective lens or exit pupil. I'm glad to see most of you understand the relationship between the two. Multiply the power into the size of the objective and you get the size of the exit pupil. 8 divided by 42 is 5.2....a 5.2 mm dot of light coming out of the eyepiece will more than cover your pupil even under poor light conditions, on an 8X42 bino . 10 divided by 42 is 4.2mm on a 10X42 bino. Give me the choice between an 8X25 with a 3.1 mm exit pupil and a 10X42 with a 4.2mm exit pupil and I'd be a fool to choose the 8X25.....of course I'd choose the 10X42....but are either of those choices ideal? When you couple a smaller exit pupil with magnified movement do you think you're going to get ideal resolution????? Now give me the choice between an 8X42 with a 5.2 mm exit pupil and a 10X42 with a 4.2 mm exit pupil I'll take that big dot of light every time. That bigger dot of light not only covers all of your pupil under almost any hunting condition but also allows for movement and misadjustment of interpupilary distance. You all ALWAYS have your binos set at the perfect interpupillary distance don't you????????
The US military has studied the human body as it relates to optics. The average maximum that the human pupil will open up to is 7mm. So designing an optic with an exit pupil of 7mm would meet ANY viewing condition thus the military standard 7 X 50. They also found that 97% of the test group could HANDHOLD a 7 X bino well enough to CORRECTLY count the lines on a 7X resolution chart.............but only 8% could CORRECTLY count the lines with a handheld 10X bino on a 10X resolution chart. All of the binos had at least a 5mm exit pupil. The test group were required to use both hands, could sit, stand, or kneel, steady themselves in any way against any part of their own body but were not allowed to lay prone or use any foreign object to help steady themselves or the bino. The test group were between the age of 18-27.
Bino's by design are handheld, so it only makes sense to use a binocular that gives you the best possible options while using them handheld. If most of your glassing is from a bluff overlooking a huge expands of land and you glass while sitting then by all means get a tripod and buy a 15X or use a spotting scope. But for that peice of glass that hangs around your neck that you use in MOST hunting conditions..... what's the best option? BTW I love those answers along the lines of "well I hunt out west were you can see for miles"?????? Well I live on earth and I can see for millions of miles with my naked eye completely through our atmosphere and see Mars. How many of you know that you can clearly see the rings of Saturn with only 20X. ..... (the larger the exit pupil the better the resolution.) By the way I live in New Mexico and can clearly see with as much detail as you can.... the same thing you're looking at with 10X...... because I use an optic that gives me excellent resolution and I CAN HOLD IT STILL ENOUGH to take advantage of that resolution.
Lets talk about hunting conditions. How many of you all are going to tell me you never use your bino with ONE hand. How many of you are going to tell me you can't "see" your heart beat or your breathing cycle when looking through your binos. How many of you are going to tell me you are as steady as a rock with a pack on your back and a bow or gun in one hand as you top a ridge and see movement on the next ridge over. How many of you are going to tell me you are as calm as a lamb when you see a tangled web of antlers on top of that buck or bull. Movement is your enemy when looking through any optic and the more power you try to handhold the more that movement is magnified. You see the question is NOT will the 10X or 12X bino produce good resolution. With most decent optics made today the answer is almost certainly YES they will produce good resolution. The question IS can you hold them steady enough to take advantage of that resolution?
Just some food for thought for those of you looking to buy a new pair of binos. And see.... we haven't even touched on FOV, matched optics, coatings, or any brand names."
