What factors determine the eye relief on a scope?

[cash_tx]

I was reading another thread on here a few days ago about the current challenge of finding new DGR rifle scopes with user-friendly eye relief; and that got me wondering, "What are the determining factor(s) of a scope's eye relief?".

I have also read on this forum how the ideal magnification setting for maximum light transmission is determined by dividing the front objective's width (in MM) by seven for a close approximation. Is there a similar set of factors that determine a scope's eye relief, and what are the easiest ones for a scope manufacturer to change in order to get a better eye relief?

PS - I hope I phrased this question in a manner that makes sense.

 

[Finprof]

I was reading another thread on here a few days ago about the current challenge of finding new DGR rifle scopes with user-friendly eye relief; and that got me wondering, "What are the determining factor(s) of a scope's eye relief?".

I have also read on this forum how the ideal magnification setting for maximum light transmission is determined by dividing the front objective's width (in MM) by seven for a close approximation. Is there a similar set of factors that determine a scope's eye relief, and what are the easiest ones for a scope manufacturer to change in order to get a better eye relief?

PS - I hope I phrased this question in a manner that makes sense.

There is a trade off between eye relief and field of view. A scout scope will have a foot of eye relief and narrow field of view. A pistol
Scope has even longer eye relief and narrower field of view.