Looking for a bright bino

[JoachimB]

Hi!

This is my first thread here, hope you can clear some things out for me, and give me some helpful information about binoculars.
Today I use an old Bundeswehr Hensoldt 8x30, which is just about the most price valuable one can buy, regarding size and sharpness. It's an excellent binocular, but I've realized that I need one for evening, early mornings, basically - I need a bright bino.

From what I understand, the main priority is large exit pupil, as close to 7mm as possible. A good 7x50 would be great, or 8x56. I wouldn't mind stepping down from 8x which I use now, to a 7x50 (with a large field of view would be even better), to easily scan off large areas fast.

Now, exit pupil isn't everthing right? Coating, number of glasses is also of great importance from what I understand. Of course a Zeiss 7x42 FL (exit pupil 6mm) is even brighter than a low standard 8x56 (exit pupil 7mm).

Weight and ergonomics is of less importance.

I've looked at Swarovski 7x50 that would make an excellent bino for less brighter evening, however some people think it's an old construction and has a narrow field of view. Although very good price.

Can you give me some good alternatives on good binoculars, within the price range of £550 to maximum of £1000. Brands would be Zeiss, Swarovski and Leica I guess.

[Fernando np]

Comparing with your 8X30 and your budget, there might be easy to find some brighter. In the present situation, why to limitate to three brands? 7x50 is among the most relaxing view. Narrow field? Compared with a 30mm objetive, of course no. Yesterday evening, I was comparing a pair of Nikon 8X32SE versus an old Docter 7X50 Binoctem, both mine. The width of field is in the same range and the smaller SE is exceptional in this point, as in others. When the light goes down, brightness isn't the only parameter. Sharpness, contrast and even power can decide the level of detail. For years I did a profesional use from a Zeiss Classic 10x40. Although less sharp, with takes toll after hours, the Docter's were able to give me ten to five useful minutes more every sunrise or sundown. Now, neither my 8X32SE nor even less my 8.5X42EL can be superpased by the Docter.
Last piece of advice. What looks brighter is usual light level isn't necessary wich had the highest performance in low light.

[Kevin Conville]

I wouldn't (necessarily) put too much emphasis on that 7mm exit pupil figure.

Here's a quick primer on that topic:
http://www.skyandtelescope.com/howto/basics/3304201.html

Twilight Factor is another important consideration:
http://www.zeiss.com/us/co/sports/home2.nsf/6f2a76c25f0237fbc12566fe003b25ff/6e6a0e7349ffc9fb85256d020078a8c8?OpenDocument

Different people will put a different value on Twilight Factor. I think it has merit.
Using the formula from the Zeiss link above, here's a few interesting specs:
8x50= 20, 7x50= 18.7, 10x42= 20.5, 8x56= 21.1

If you can hold them, a 10x42 will perform pretty well in low light. Of course, the younger you are the more you can take advantage of a larger exit pupil.

At 52, my eyes don't dilate to 7mm. I've measured them. I also don't hold 10x binos very well. So, for me 8x50s would be a good choice for a low light bino.

[Swedpat]

Hi Joachim,

It would be easier to write on swedish, but then the other would not understand...

The Swarovski SLC 7x50 is an excellent binocular. I recently purchased the 7x42 model. If I had been younger I would possibly chosed the 7x50 model. But I am 40 years old now and I am quite sure that I cannot make use of the 7mm exit pupil anymore.
Usually the maximal dilated eye pupil goes below 7mm after 30 years old, but this is also personally. I think I have about 6mm, maybe a bit more.

The Swarovski 7x50 has the largest sweet spot of all binoculars I have tried (I experienced full sharpness and undistortioned image until likely 99% of the field when I tried it some years ago), even better than the 7x42, which is best in it's class.

But the apparant field of view is narrower than the 7x42. I don't know your age, but if you can make use of 7mm exit pupil I think the 7x50 is a good choice. If you can make use of 6mm or less, the (or a) 7x42 is a better alternative. You will have the same perceived brightness but larger field of view.

Regards, Patric

[Swedpat]

Twilight Factor is another important consideration:
http://www.zeiss.com/us/co/sports/ho...8?OpenDocument

Different people will put a different value on Twilight Factor. I think it has merit.
Using the formula from the Zeiss link above, here's a few interesting specs:
8x50= 20, 7x50= 18.7, 10x42= 20.5, 8x56= 21.1




The information from the Zeiss site actually is very misleading. Higher twilight performance isn't the same as brighter image, which the pictures will make the impression of. The pictures of the fox show a difference of relative brightness and not a difference of twilight performance.

Twilight performance is a very finite expression which cannot be compared like relative brightness index. The twilight performance formula is very static and can be strictly compared only between optics with about the same brightness index (exit pupil). Relative brightness index is the BASIC rule for low light performance.

Regards, Patric

[Kevin Conville]

Yeah, what does Zeiss know about it!?
True, because the image of the fox is of equal size indicating equal magnification, the only way to increase the twilight factor would be an increase in lens size which would increase both relative brightness and twilight factor. In this way Zeiss does do a bit of a disservice in that they don't clearly show where relative brightness leaves off and twilight factor starts, so to speak.

I knew this would be controversial. I said different people will place different value on twilight factor.

I'll give you one example that I experienced recently...

I had a pair of 7x42 Ultravids that I was comparing to a pair of 8x32 Trinovids, at night under street lights. Reading license plates and street signs, I compared what I could actually make out and discern. Not brightness per se, but identifying what I was looking at.
The 8x32s allowed me to read more, and easier! Not by much mind you, but there was a difference in favor of the 8x bino.

Now this doesn't jibe perfectly with twilight factor as the 7x42 has about 1 point greater TF, but it is telling about the importance of even 1 point of magnification and magnification plays a disproportionate role in twilight factor. The exit pupil of the 7x42s is 6mm and the 8x32s 4mm. This gives the relative brightness edge to the 7x42s, but I couldn't see more with them.

There are a lot of variables in play with binoculars and the relative brightness value you refer to, after a point, can only be made use of if one has the eyes for it. BTW, contrary to your statement, I think that the relative brightness index is a more static figure than twilight factor which attempts to explain why one can see more with a theoretically less bright bino.

After one determines what is the greatest usable exit pupil for them, greater magnification will allow you to see more.

[ceasar]

Alot depends on the make and model of the binocular. For instance, my Nikon 8 x 32 SE (a porro prism) is clearly brighter in daylight, overcast conditions than my Leica 7 x 42 Trinovid BN (a roof prism) is. Both, however, are more than adequate for general use. If I wanted to use the binocular exclusively at night, though, I would choose the Leica because of it's larger exit pupil. I much prefer it for casual astronomy.
Bob

[Swedpat]

Kevin,


True, because the image of the fox is of equal size indicating equal magnification, the only way to increase the twilight factor would be an increase in lens size which would increase both relative brightness and twilight factor. In this way Zeiss does do a bit of a disservice in that they don't clearly show where relative brightness leaves off and twilight factor starts, so to speak.


Yes, in the example of Zeiss webpage the image scale is the same and the image much brighter in the other picture. This is as you say because of larger aperture. And at the same time the twilight factor will increase.
The misleading of Zeiss example is that it gives the impression that higher twilight factor is the same as brighter image. A larger aperture will increase as well the brightness and the twilight factor, while a higher magnification will increase the twilight factor but worse the brightness.



I knew this would be controversial. I said different people will place different value on twilight factor.

I'll give you one example that I experienced recently...

[COLOR="DarkSlateGray"][I]I had a pair of 7x42 Ultravids that I was comparing to a pair of 8x32 Trinovids, at night under street lights. Reading license plates and street signs, I compared what I could actually make out and discern. Not brightness per se, but identifying what I was looking at.
The 8x32s allowed me to read more, and easier! Not by much mind you, but there was a difference in favor of the 8x bino

Now this doesn't jibe perfectly with twilight factor as the 7x42 has about 1 point greater TF, but it is telling about the importance of even 1 point of magnification and magnification plays a disproportionate role in twilight factor. The exit pupil of the 7x42s is 6mm and the 8x32s 4mm. This gives the relative brightness edge to the 7x42s, but I couldn't see more with them.


I think you are completely right here. The purpose with the twilight factor is to make a scale for the performance of seeing details during lowlight conditions, but not dark. The comparison you made wasn't according to what you tell under real dark conditions.

But suppose that you compare the 8x32 and 7x42 in real darkness, and instead of comparing reading illuminated plates try to see details in the forest at night. Then you may experience that situation when the 4mm exit pupil of the 8x32 would not provide any detail at all, but just darkness, and the 6mm exit pupil of the 7x42 actually would unveil some details because of the 2,25 times higher brightness.



BTW, contrary to your statement, I think that the relative brightness index is a more static figure than twilight factor which attempts to explain why one can see more with a theoretically less bright bino.

After one determines what is the greatest usable exit pupil for them, greater magnification will allow you to see more.



I am not sure if my word "static" is the best in this issue. But what I mean is that the twilight factor is dependent of the relative brightness to have any value. When the brightness goes below such a limit (the limit is depending of the level of lowlight) you will se nothing else than darkness.

One example:

A spottingscope can be advertised like this:
20-60x60. Twilight factor: 34,6-60.

This is a case when the statement of the twilight factor isn't really relevant. Even with the lowest magnification the spottingscope provides a brightness comparable to a 7x21 binocular and it's at the limit to be useful during lowlight conditons. With the highest magnification the twilight factor is better. But forget to use a 1mm exit pupil during any lowlight conditions!
Magnified darkness=darkness.

During some circumstances the twilight factor is useful to get an understanding of the performance in lowlight. During other circumstances it can be totally worthless. The twilight factor isn't a reliable way to find out the lowlight performance.

The relative brightness index, however, is always useful for a direct comparison. Every binocular, undependent of aperture or magnification, with the same exit pupil provides the same image brightness providing equal light transmission and that you can make use of the exit pupil size. Therefore I consider the relative brightness index to be the basic method of measuring lowlight performance. When using the twilight factor you have to take in consider the circumstances and be sure that the relative brightness is adequate.

Excuse my faulty english!

Regards, Patric

[Kevin Conville]

Patric,

No conflict of agreement here.

Twilight factor being useful during "twilight", not full night. I think when most people on these forums refer to an optic performing in low light, they usually mean twilight.

Also your point made with the spotting scope is valid. Twilight factor seems to be most useful used for binoculars in powers and sizes common for hand-held use.

And BTW, your English is excellent and vastly superior to my Swedish! ;^)

[Alexis Powell]

I perhaps disagree in part with the point about the scope. Magnification is of great help in seeing and making sense of birds in low light conditions, even at the expense of exit pupil or brightness. When I'm birding at the limits of seeing (very low twilight), I make heavy use of my scope at 30x (I agree that 60x may leave your eye with too few photons to see with!). It is much superior to 8x42 binoculars for making IDs at close distances where I wouldn't normally use a scope.

--AP

[Kevin Conville]

Yeah it's the extreme end of the spectrum where the spotting scope starts to fall down.
A 60mm scope at 60x in near dark won't be great though it will have a twilight factor of 60. It's brightness index is 1 however!

One does need a certain number of photons to make things happen.

I hear you though Alexis, an 80mm scope with a 30x eyepiece on it is a formidable low light optic for sure. Twilight factor- 49, Brightness index-7

[Swedpat]

Alexis,

I understand what you mean. In your example the outer light conditions is adequate for the 2,67mm exit pupil. You can notice details though the image is very dim, because the image brightness is still adequate to see details. In this the higher magnification helps. But a bit less light and you would not see these details, and you may gain by increase the exit pupil though the magnification will be lower.
I think the difficulty with the twilight factor is also that it's quite relative what we mean with "low light".

In a binocular brochure I have (I have a collection of binocular brochures since 20 years ago) the 10x25 model is described as (for beeing a compact) useable during lowlight conditions due to it's relatively higher twilight factor in comparison to the 8x20 model. The 10x25 was described to be more useful during low light conditons than the 8x20.

I don't agree with such a statement. In every circumstance we with a given exit pupil are able to notice ANY detail, we will see better with a higher magnification. This has actually not to do with twilight performance. A 10x25 is better than a 8x20 as long the 2,5mm exit pupil enable to see anything at all.

Regards, Patric

[JoachimB]

Hi Joachim,

It would be easier to write on swedish, but then the other would not understand...

The Swarovski SLC 7x50 is an excellent binocular. I recently purchased the 7x42 model. If I had been younger I would possibly chosed the 7x50 model. But I am 40 years old now and I am quite sure that I cannot make use of the 7mm exit pupil anymore.
Usually the maximal dilated eye pupil goes below 7mm after 30 years old, but this is also personally. I think I have about 6mm, maybe a bit more.

The Swarovski 7x50 has the largest sweet spot of all binoculars I have tried (I experienced full sharpness and undistortioned image until likely 99% of the field when I tried it some years ago), even better than the 7x42, which is best in it's class.

But the apparant field of view is narrower than the 7x42. I don't know your age, but if you can make use of 7mm exit pupil I think the 7x50 is a good choice. If you can make use of 6mm or less, the (or a) 7x42 is a better alternative. You will have the same perceived brightness but larger field of view.

Regards, Patric


Thanks Patric.
I'll look more into the SLC 7x50 and see how it'll work in more dark conditions.
The price is quite ok, if bought from the UK. Thanks everyone for your help.
Btw, Patric, I saw a Common Crane this weekend, feeding out in the fields. A bit early don't you think? I live in Jamtland.

[Swedpat]

Joachim,

I am actually not an expert on birds...common crane, is that a trana?

Regards, Patric

[JoachimB]

Joachim,

I am actually not an expert on birds...common crane, is that a trana?

Regards, Patric

Yes it is.