Daytime brightness of binoculars (1 Viewer)

[tenex]

Why may someone think one binocular is "brighter" than another in daytime? This issue comes up repeatedly, and often doesn't resolve to everyone's satisfaction. (Twice in the last few days: MHG 8x42 vs NL 8x32, and NL 10x52 vs 8x42.) Sometimes it degenerates into an "I know what I see" argument without even getting into possibly relevant details. (This happens with depth of field too.) So can we at least establish a complete reference list of what these factors might be? The first two are obvious:

1. Transmission (manufacturers' methods may vary slightly, but specs probably remain comparable)
2. Effective exit pupil (smaller of eye and binocular exit pupil)

But there are still cases that seem to defy simple explanation, where someone thinks the bigger bin is brighter even in daylight, or the one with the smaller EP is brighter. So what other factors can be involved?

3. Color cast -- cooler can look "brighter"
4. Conditions -- is the observer standing or looking into shadows (not really "daylight", pupil is more dilated)
5. Poor comparison -- not looking at exactly the same view when switching back and forth (a difference in FOV could affect this too)
6. Poor observation -- believing is seeing?

Anything else? Because I take it for granted that when someone says one bin is brighter, they do have that impression. The question is, why would they?

 

[Maljunulo]

We used to call such arguments “hand waving”.

They typically involve no objective data whatsoever.

 

[wllmspd]

I bought a secondhand pair of nikon 8x30 E2 to replace a secondhand pair of 8x30E and compared them before I sold the E. the view through the E2 was definitely brighter (and a bit wider too). The difference was probably due to improvements in the coatings over the time beteeen manufacture.

Peter

 

[Swedpat]

Why may someone think one binocular is "brighter" than another in daytime? This issue comes up repeatedly, and often doesn't resolve to everyone's satisfaction. (Twice in the last few days: MHG 8x42 vs NL 8x32, and NL 10x52 vs 8x42.) Sometimes it degenerates into an "I know what I see" argument without even getting into possibly relevant details. (This happens with depth of field too.) So can we at least establish a complete reference list of what these factors might be? The first two are obvious:

1. Transmission (manufacturers' methods may vary slightly, but specs probably remain comparable)
2. Effective exit pupil (smaller of eye and binocular exit pupil)

But there are still cases that seem to defy simple explanation, where someone thinks the bigger bin is brighter even in daylight, or the one with the smaller EP is brighter. So what other factors can be involved?

3. Color cast -- cooler can look "brighter"
4. Conditions -- is the observer standing or looking into shadows (not really "daylight", pupil is more dilated)
5. Poor comparison -- not looking at exactly the same view when switching back and forth (a difference in FOV could affect this too)
6. Poor observation -- believing is seeing?

Anything else? Because I take it for granted that when someone says one bin is brighter, they do have that impression. The question is, why would they?

Yes, there are some factors who have impact on the perceived brightness. You mention some important things.
Theoretically all optical devices with same exit pupil and light transmission have the same brightness.
The perceived brightness can still differ. For example: if you watch a certain object in a 10x25 and 20x50 they both have same exit pupil.
If they have the same apparant field of view 10x25 has twice the true field of view which means 4 times more area of the reality is visible.
If you for example observe an even painted and illuminated wall, or blue sky without clouds there is no difference, it looks the same.
But if you observe a landscape or buildings the image is not evenly illuminated. Depending on the relation between dark and bright objects visible in the FOV, the eye pupil can vary in size.
If the FOV with 10x25 shows both a forest area and a sun mirrored sea and with 20x50 only the forest, you may find the forest looks brighter in the 20x50. But if you aim the 20x50 so only the sea is visible, the sea may look brighter in the 10x25. And as you mention: different apparant field of views can give a difference in perceived brightness even with same configuration.

Another example is if you observe a dark area at night. With a narrow FOV only the dark area is visible. But with a wide FOV you cannot avoid street lights or other light sources to be in the FOV. Which strongly destroys the view of the dark area.
Here a 20x50 can be perceived brighter than a 10x25. And the same with two different 20x25s: the model with narrower FOV can be brighter because it can avoid the light sources.
Actually I have a theory that the fact many 7x50s have very narrow AFOV is intentional.
These are the night glasses and with a narrow FOV the chance to isolate dim areas increases.
Yes, the topic in this thread is daytime view but I mentioned this as well, because it's the same optical principle.

 

[Gijs van Ginkel]

Since this topic is discussed over and over I have made a review paper about it that is published on the WEB-site of House of Outdoor. Brightness is a psychological phenomenon. For example dark red is considered by our eyes/brain less bright than green (if the photon fluxes of both colors are identical) but you can read that in the review paper.
Gijs van Ginkelk

 

[YuShan]

I have winged eyecups on my EL 8.5x42 that blocks out light coming from the sides. I find that a great improvement, getting rid of distractions. But I just realised that perhaps it also gives the impression of more brightness because no stray light prevents extra dilution of the pupils.

Btw: I also agree that more realistic color (i.e. white = white) vs warm colour (i.e. drop off in the blue) also appears brighter.