Too much eye relief? (1 Viewer)

Just a quick question - when I look through my Leica 8x20 compacts I see a perfect Sharp edged black circle surrounding whatever I'm looking at.

I bought a pair of Optolyth 7x42 for low light work and to get the same effect as the Leicas I have to get the inter pupillitary distance spot on and hold the bins away from my face (slight exaggeration) is this "shadowing" at the edges normal or am I missing a trick?

JonMartin said:

Just a quick question - when I look through my Leica 8x20 compacts I see a perfect Sharp edged black circle surrounding whatever I'm looking at.

I bought a pair of Optolyth 7x42 for low light work and to get the same effect as the Leicas I have to get the inter pupillitary distance spot on and hold the bins away from my face (slight exaggeration) is this "shadowing" at the edges normal or am I missing a trick?

Click to expand...

The difference lies in the different exit pupils of the two binos.

The 8x20 has an EP diameter of 2.5 mm (20 mm/8 = 2.5 mm) which most likely is smaller than you own pupils in most light conditions. Therefore, the field of view becomes limited by the binoculars exit pupil.

The 7x42 has an EP diameter of 6 mm (42 mm/7 = 6 mm) which is larger than most eyepupils in daylight. Therefore the field of view often becomes limited by the eyes own pupil which has a soft edge. This condition also makes it more critical to fit the bino's EP with the eues pupils as you noted. (The problem is less severe in low light.)

Cheers, Jens.

Jens you're a genius - that explains the symptoms perfectly.

Many thanks, Jon.

If the eye cups are screw out types, I have screwed them out half way to get the clear edge visible.