Comparing 10x32 NL with 8x42 NL, some (not ground breaking) thoughts... (1 Viewer)

[William Lewis]

Hi Grackle

I'll have another go, maybe my last one - we'll see!

If you look at whatever is in front of you and then move your eye closer to it- does it get brighter? According to your theory it should.

 

[grackle314]

Hi Grackle.

As a little thought experiment consider that by your maths a higher magnification will almost always lead to a brighter image as long as your not going below the eyes pupil size?

What you may like to consider is the magnification as a "crop" factor, i.e your cropping a section of the gathered light and magnifying it when you go from say a 7x42 to a 12x42. It will still be as bright as long as the eye pupil is above 3.5mm in this case with all other things being equal. You may well see more detail but it will not be because it's brighter.

Will

Hello William Lewis, yes, a higher magnification will almost always lead to a brighter image as long as the exit pupil is larger than the eye pupil.

And, yes, you may consider the magnification includes a "crop" factor along with the luminance factor as you say. The 12x42 will be brighter than the 7x42 within a 3.5 mm eye pupil by 144/49 ~ 3. And one will see smaller details in the 12x due to the magnification increase as well.

 

[grackle314]

Hi Grackle

I'll have another go, maybe my last one - we'll see!

If you look at whatever is in front of you and then move your eye closer to it- does it get brighter? According to your theory it should.

Hi William Lewis, in the case of bringing one's eye close to an object, as long as the luminance remains constant the object will not get brighter. The object takes up larger solid angle in viewing as one gets closer but that does not necessarily increase the luminance into the eye.

 

[William Lewis]

Hi William Lewis, in the case of bringing one's eye close to an object, as long as the luminance remains constant the object will not get brighter. The object takes up larger solid angle in viewing as one gets closer but that does not necessarily increase the luminance into the eye.

It does indeed, the same holds true with a binocular.