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8x or 10x for low light? (1 Viewer)

M

mwnold

Well-known member
Guys, I am hunter and looking for a bino that will give me best performance in low light situations. I enjoy preseason scouting the edges fields and trying to catch a glimpse of the big buck that will only sneak out when it is nearly dark.

I want a x42 due to size. I will carry them to my tree stand and use them for archery hunting.

What would best for my purposes - a 8x or 10x? The EP of the 8x is larger, but the 10x has a higher twilight factor. All things being equal which one delivers better twilight performance?

Thanks

Mike
 
I'm not resally sure of the relevance other than a marketing ploy maybe = the square root of the [ magnification x objective ] is just a math equation. I'd opt for a larger exit pupil every time but that just my ignorance probably.
 
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I have it narrowed down to three - Zeiss FL T, Nikon EDG, Swaro SLC HD.

The Zeiss will most likely win the day. It has the better brightness and can be found at a reasonable price these days.

I read a quote somewhere, and I apologize if I have stolen it from someone here, but in regards to making a bino selection you should "get the largest objective lens you are willing to carry, and get the largest magnification that you can hold steady". In doing that you will have the best low light optical performance for your given situation. For some reason that just seems to make sense.
 
I hadn't had enough coffee to get going when I first posted. Are you confusing twilight factor with the brightness factor? The brightness factor is the exit pupil squared. 8x = 5.25x5.25 = 27.56. For 10x it's 4.2x4.2 = 17.6. That's the set of numbers you want to work with.

A lot of big game outfitters out west will use an 8x56 bin. A bit hefty but with a brightness factor of 49 - those muleys along the slopes are a little easier to see - ymmv.
 
The brightness factor is just another way to express the exit pupil. It is the EP squared. What I am questioning is the twilight factor. Which is another mathematical equation that estimates the performance of resolution in low light conditions. According to the TW principle a 10x will out resolve a 8x in low light. With everything else being the same of course.

I am just curious if anyone has any real world experience with this. Does a 10x perform better than 8x in very low light conditions?
 
I am just curious if anyone has any real world experience with this. Does a 10x perform better than 8x in very low light conditions?[/QUOTE]

I would suggest yes only if the exit pupil size is the same i.e. 10x50 better than 8x40.

If you are comparing bins with similar objective size i.e. 8x42 vs 10x42 I would suggest the 8x.
 
Robert Wallace said:
I am just curious if anyone has any real world experience with this. Does a 10x perform better than 8x in very low light conditions?
Click to expand...

I would suggest yes only if the exit pupil size is the same i.e. 10x50 better than 8x40.

If you are comparing bins with similar objective size i.e. 8x42 vs 10x42 I would suggest the 8x.[/QUOTE]
Agreed! Bryce...
 
mwnold said:
I have it narrowed down to three - Zeiss FL T, Nikon EDG, Swaro SLC HD.

The Zeiss will most likely win the day. It has the better brightness and can be found at a reasonable price these days.
Click to expand...



I have the Zeiss Victory FL T* - and in low light they are the best I've ever owned (including a couple of Swarovski bins). I have a Swarovski 3-9x36mm scope on my ML but I can see more with the Zeiss than I can realisticly shoot in the dark.
 
You can do a little experiment and see what works best for you. Try watching deer on an open field on a clear evening as the light fades to dark. Through a variable 3-12x50 scope, at last light you can see a bright background and a good profile of a deer against it with the scope on 7x (7.1mm EP), but relatively little detail of the deer itself. However, zoom up to 12x (4.2mm EP) and while the field of view is smaller, the deer itself appears brighter and you can start to pick out much more detail. So while the twilight factor may be a meaningless number, the idea of higher magnification at low light (with sufficient light coming through an adequate exit pupil) has merit.

Having said all that, I personally find a 4.2mm exit pupil hard work on the eyes in a 10x42 when you approach last light. If you are unwilling to go larger than 42mm (e.g. to a 10x50 or 10x56), I would probably choose the 8x42 for that reason.
 
As an anecdote, I know many professional deer managers who work for landowners or the Forestry Commission (in the UK, our doe and buck seasons run such that you can hunt at least one of the 6 deer species 365 days a year) who previously swore by their 7x42 BGATs and SLCs, yet ultimately traded 'up' to 8x42 FLs and 8.5x42 ELs. I know very few who use 10x42s except on the open hill in Scotland, so I take from that that the higher magnification helps a bit in low light, but that the 5mm exit pupil benchmark is a sound one...
 
Thanks for the good info. I used to have a pair of 8x56 Steiners that were like having night vision. But I ultimately sold them. They were too big to carry on a hunt and I seemed to always question the magnification for the longer range viewing.

You said that 10x42's can be hard work on the eyes. I usually do not spend a lot of time behind the glass. I can usually locate deer with my eyes at the ranges that I am dealing with. I will then put the glass on them for identification and detailed viewing. My point is that in my area of the world I don't spend a lot of time "glassing".

I am trying to weigh all the variables for my application - exit pupil size, magnification for a steady hold, brightness and low light capabilities, size/weight, etc... The hunt is always more fun than the kill!

Thanks again to everyone for helping.
 
JabaliHunter said:
You can do a little experiment and see what works best for you. Try watching deer on an open field on a clear evening as the light fades to dark. Through a variable 3-12x50 scope, at last light you can see a bright background and a good profile of a deer against it with the scope on 7x (7.1mm EP), but relatively little detail of the deer itself. However, zoom up to 12x (4.2mm EP) and while the field of view is smaller, the deer itself appears brighter and you can start to pick out much more detail. So while the twilight factor may be a meaningless number, the idea of higher magnification at low light (with sufficient light coming through an adequate exit pupil) has merit.
Click to expand...

Well it seems I learn something every day but I'm going to have to try that experiment myself. It seems like you would magnify any distortion rather than improve it - I could be wrong. I have a 6-24x44mm Sightron II Big Sky on my .204 Ruger, then I ought to be able to see any cavities on a woodchuck's front teeth in low light then . . .
 
tpcollins said:
Well it seems I learn something every day but I'm going to have to try that experiment myself. It seems like you would magnify any distortion rather than improve it - I could be wrong. I have a 6-24x44mm Sightron II Big Sky on my .204 Ruger, then I ought to be able to see any cavities on a woodchuck's front teeth in low light then . . .
Click to expand...

Well I don't know about distortion; I suppose that will depend on the glass. Your scope is also more powerful and so I don't know what would happen as magnification increases and exit pupil decreases below 4.2mm because I haven't tried that.

I may not have described it well, but it is the same effect as for example looking out across a field in the dark and not seeing anything but the dark with the naked eye, yet moments later lifting binoculars to your eyes to reveal animals grazing in the field.

In some ways it seems counter-intuitive as you would expect to turn down the magnification to increase the exit pupil and let more light through as the ambient light level falls. But in the deer example at last light you start with a bright field of view at the lower magnification, but the deer is mainly observed as a silhouette. You can see the deer, but can you tell whether it is a doe or a small buck that has cast its antlers? As you increase the magnification, the field of view may not be as bright but the level of detail observed on the deer increases. Now you can pick out identifiable features, even if colours can't be distinguished because the light level is too low.
 
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I think you have described well the principle of the twilight factor. So in theory, the 10x will perform better than the 8x in low light conditions because it has the higher twilight factor.

Think about the extreme of spotting scopes. They have very small exit pupils. But they have large magnifications and thus high twilight factors. They perform very well in low light conditions.

A 20 x 60 scope has a twilight factor of 35 and an EP of 3. An 8x56 bin has a TW of 21 an EP of 7. The scope will easily outperform the bino in low light. Even though it has half the exit pupil size.
 
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Tp:

This thought is right on. That is how I see it. I have found a quality 10x50 binocular
will give me the best view I can get in low light, and tops another in 8x42 or 8.5x42
when used then. Aperture is important, and so is power, but it has to be in a quality
optic or it does not mean much.

I would not include rifle scopes in this discussion.

Jerry
 
Roy is saying that the TW theory is rubbish without providing any proof. The TW theory says if a 7x50 and 10x42 are indentical in their construction then the 10x42 will provide better image resolution in low light.
 
mwnold said:
Roy is saying that the TW theory is rubbish without providing any proof. The TW theory says if a 7x50 and 10x42 are indentical in their construction then the 10x42 will provide better image resolution in low light.
Click to expand...

Have no idea what Roy said but I glass my clover fields on a regular basis from the beginning of twilight to total darkness.....and aperture rules. I always opt for one of my binos with an exit pupil of 5-7mm. If glassing from my truck I often use one of my 10x50 porros but if I want a carry bino with excellent light gathering I opt for my 7x42 EDG.

I'll try to send you a pm later with a trail cam pic of what I've been watching walk into my clover plots at the edge of dark.....very nice;).

Steve
 
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