Effect of Magnification on Light Output from a Binocular (1 Viewer)

[Swedpat]

The answer is that twice the light will reach your eye. It will still have the same intensity, the image will just be bigger.

By saying equivalent AFOV between 8x and 10x is the same as saying that the 10x true FOV is 64% the size of the 8x FOV

So: because the objective lens has a total light gathering power, making use of the total light amount requires that the AFOV is the maximum size so the field stop puts the limit, right?

But the relative brightness always is directly related to the area of the exit pupil, that is also what RBI index shows. So it is not necessary an advantage to make use of the full light gathering of the objective.

For seeing details in dim conditions it can then be an advantage not to make use of the full light gathering of the objective, by using a narrow AFOV eyepiece.
This because the less light reaching the eye, the better the eye can actually see the details who are in the FOV. Also for astronomy a narrow AFOV is an advantage if the purpose is to see very dim objects. But for the enjoyment of viewing a very wide AFOV is better.

 

[tenex]

It's just too difficult to guess exactly what another person may be confused about, or whether they're really trying to say something a bit different. I wanted to suggest that everyone just stop going around in circles and read a good book about how binoculars work, but the term brightness doesn't even occur in the index of Holger's Handbook[*]. (Brightness only becomes relevant indirectly regarding resolution in low light.) Transmission having long since reached a satisfactory level, minor differences in perceived brightness are unimportant. Why then are people going around opining in the first place that one bin "looks brighter" than another in daylight, and why does this irrelevant line of argument keep being proposed to explain it?

[* - Edit: but luminous flux is discussed on pp.143-145, in similar terms to post 27 above]

 

[Maljunulo]

It's just too difficult to guess exactly what another person may be confused about, or whether they're really trying to say something a bit different. I wanted to suggest that everyone just stop going around in circles and read a good book about how binoculars work, but the term brightness doesn't even occur in the index of Holger's Handbook. (Brightness only becomes relevant indirectly regarding resolution in low light.) Transmission having long since reached a satisfactory level, minor differences in perceived brightness are unimportant. Why then are people going around opining in the first place that one bin "looks brighter" than another in daylight, and why does this irrelevant line of argument keep being proposed to explain it?

If everyone stopped going around in circles, this place wouldn’t last 48 hours.

“That which is perceived is by definition subjective.”
-Me-

 

[Swedpat]

I was talking about an extended object that fits within the FOV. The image you see of it through the 10x bino is obviously bigger than the 8x bino's (unless it is a point source like a star).

If you want the same brightness across the magnified image of the object, you need more total light for the 10x mag bino vs for the 8x.
Yes, that is correct. And it requires as larger aperture as the magnified object is larger.

In daylight, the eye's pupil is smaller than either bino's exit pupil. But because the 10x bino's exit pupil is smaller than the 8x, a higher percentage of the light gathered by the 42mm objective actually reaches the eye's retina.
Yes, that is correct. More light will reach the eye when observing a light source like the moon or a lamp. But the higher portion of the objective which is used with 10x remains proportional to the magnification. Therefore the relative brightness remains the same. So if observing an even illuminated surface which covers the entire FOV and both 8x and 10x have same AFOV the light amount reaching the eye is the same.

 

[agus_m]

Yes, I agree on that. But in my view, the whole confusion was if grackle314's results made sense or were a bunch of misconceptions. To me they made sense and I was trying to explain myself.

I get it, talking about these topics is a bit confusing due to several concepts that are similar, but not the same. Like "brightness", "luminance", "power density", etc. Because of this I have a hard time trying to understand what each user is trying to say, I have to re-read the text sometimes. This is not a physics forum, so it is expected that some wouldn't know the difference in the terms. Some times we could be saying the same thing and we don't know. There is no problem with that if we communicate respectfully.