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Isnt exit pupil objective diameter divided by magnification?

So I will answer my own question, yes it is. Magnification is a factor in determining exit pupil. For instance look through a variable power riflescope and turn the magnification up as you are holding it at arms length, you will see the aperture of light (exit pupil) decrease as you increase the magnification - hence being directly related. My point was the same point you were making, More power will allow you to resolve greater detail in low light given all other factors being equal. For example I have a pair of Swarovski 7x42 SLC and 10x42 SLC with the same lens coatings. The 7x42 is noticeably brighter in low light but the 10x42's allow me to see detail better in the same light.

So I think I do understand exit pupil.

Just walked back inside with my 10x42mm Leica Geovids, glassed clearly for deer in the North pasture up to the tree line at 600 yards, would need a small flashlight to spin the turrets in light that low.

Nope. Magnification is what makes the image larger, not exit pupil. Your eye is capable of only so much dilation and the older you get, the less eyes will dilate. Magnification and objective lense size define the exit pupil or ability for light transmission, not light gathering. 7X42 will allow more light than a 10X42, and the 10X may show more detail, but it will be limited on how much of that detail is even visible as light wanes in the latter part of the day.

However, if your eyes are only capable of 5mm of dilation, more light won't change that as there are limits on what light is available and how much the eye and detect. So, all things being equal in optic quality, a 10X50 should be comparable to an 8X40 under the same lighting conditions, but magnification won't transmit more light.

You are contradicting yourself-

In one post you say-
Magnification is not directly related to exit pupil...

then in your last post you say-
Magnification and objective lense size define the exit pupil


So I reiterate magnification is a determining factor in exit pupil. We can agree that I was right on that-

I never said exit pupil makes the image larger, I dont know where you got that. There is a difference in between a 10x50 and an 8x40 under the same lighting conditions, its called twilight factor

"Twilight factor- theoretical estimation of how much detail can be seen in low light and is estimated by first multiplying the magnification by the objective lens size, and then taking the square root of that product. So twilight factor can increase with an increase of either magnification and objective lens size or both. The twilight factor can also remain the same if the magnification is doubled but the objective size is cut in half (and vice versa).

For example, the 8 X 50 binoculars would be 8 times 50 =400, then the square root of 500 = 20.0 value for twilight factor. The twilight factor for the 10 X 50 is simply 10 times 50 = 500 and the the square root of 500 = 22.4, so the 10 X 50s have a 12% detail advantage over the 8 X 50s in low light."

As in my example, reading in a room with a 20 watt bulb- closer means seeing greater detaill. The 8x50 binoculars will have a greater exit pupil (brighter) but the 10x50 will enable you to see greater detail in the same light

If you can afford the swaro, get it. All things being equal, bigger objectives are better for absolute last light. I lot depends on how you like big glass on your neck, and how long you have to walk to get to stand.

I think the swaros are a couple grand. I probably won't drop that much cash for a binocular used just for deer. I'd like to keep it under a grand. I was thinking the Zeiss Conquest would probably work well for me, but I see that lots of folks are recommending Tract.

I can see deer at very near dark with my current Nikons and can place an accurate shot on them with my VX6 with red dot, but what I am looking for is better light/detail so I can determine size of the horns before I shoot.

Thanks,

Dan

This. My geovids are dang near night vision. I can often see deer with them that I can't see with the naked eye because it is too dark. They are expensive but you get what you pay for.

You've got to be a pretty "old" adult to be worrying about your eyes not dilating to at least 5mm.

Get the biggest objective with the most magnification with at least 5mm exit pupil that you can afford. It will allow you to see the most in low light.

Find some way to hold it steady (like a tripod) and you will see more also.

With that stipulation it gets a little tough. I'd look for a used set of alphas or maybe a Cabela's branded meopta on clearance. The Leica rf bino Doug had for $999 would have worked well - and you would get a finder to boot.

You'll get better low light performance out of a pair of first tier 10x42's than you will a second rate pair of 10x50's. When money is the limiting factor always choose quality first and objective size second. Only go for the big objective if you've maxed out the glass quality, only then will you be able to see a difference.

If you watch the classifieds and ebay you can occasionally grab some used 42mm swarovski slc's or equivalent leica's for $1K. You'll get better low light performance out of them than the conquests.

https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/12329475/Searchpage/4/Main/844659/Words/%2BLeica+%2B10/Search/true/swarovsks-slc-10x42-and-ats-hd-65mm-spotting-scope#Post12329475

A little above your desired range, but this is the route I would go ...

Not sure why it didn't hyperlink; also agree with everything crow hunter said above.

One will see more detail in low light with a 10x42 verses a 8x42 considering they are of the same quality.. The image may be brighter with the 8x42 because of larger exit pupiI(if your eyes can use it) but the resolution will be better with the 10x42.

The 10x42 has a higher twilight factor.

A high quality 10x56 would be a top performer in low light for detail recognition An ideal combination of large exit pupil and magnification.

I see very little difference in brightness in low light these days between identical 8x42 and 10x42 binoculars. I do see the superior resolution of the 10x in low light. I have 20/20 vision but am approaching fifty years old.

For under a Grand: Some good glass, not top of the line break the bank good, but very usable binoc's.


https://swfa.com/pentax-8x43-dcf-sp-binocular.html

https://swfa.com/nikon-8x42-monarch-hg-binocular.html

https://swfa.com/leica-8x42-trinovid-hd-binocular.html

https://swfa.com/vortex-8x42-razor-hd-binocular.html

I imagine the 10x56 Conquest will serve you very well, Dan.

Bingo to what Timberbuck said.

More magnification will show you greater detail, provided you have enough objective size to give you an adequate aperture or exit pupil. That is exactly what the 10x56 will do for you. It may not be as bright as the 8x56 to most hunters, however it will show you more detail.

I paid $300 a month for 6 months for a pair of Swarvoski SLC 10x50s in 2007. Never regretted it, still don't. I expect to use them many more years for low light hunting. Most people can't hold anything above 10 power steady enough to get any good out of it. Tripods are another subject. Look for a high quality used pair in the 10x50. Swarvoski, Zeiss, Leica. etc.

Thanks all. Maybe i'll just suck it up and bite the bullet on some Swaros or Leica. Hell, it will be the last set I ever own since I am 56!

I appreciate all the feedback.

I have 7x42 Leica Ultravid HD, 10x56 Zeiss Conquest HD, and 10x54 Zeiss HT.
I love the Leica, but when I really want to see detail in very low light either of the Zeiss are the choice.
For my purposes, I see very little difference in the view comparing the 10x56 Conquest HD and the 10x54 HT.
The HT is slightly smaller and slightly lighter, and about a thousand dollars more.
IF size and weight is not a factor the Conquest HD is a good choice for me.

Buy once cry once....I have a pair of Swarovski 7x42 SLC purchased new in the mid 90's, for me they are about the best all around pair of binos I've ever owned. I have a Pair of 10x50 SLC's as well which help with defining objects at greater distances but for all around quality, ease of use and low light conditions the 7x42 work best for me. Having said all of that a see a pair of 8x42 EL Range in my future !!