Eye Glasses & Eye Relief (1 Viewer)

Negative eye glasses extend the effective eye relief. Does anyone know just how large this effect is? Is there some kind of formula or a rule of thumb? Thanks.

I think it will depend on the strength of the lens and the position along the axis.
Possibly even the thickness also.

Hi Lightbender,

The best (and only) technical analysis of this topic that I'm aware of is in Smith & Atchison's book "The Eye and Visual Optical Instruments" (1997). I've attached pgs 323-4, where the discussion starts at sect. 14.1.5. But for a fulsome understanding, it's unfortunately necessary to reference several equations scattered throughout the book.

Elsewhere this discussion also couples up with Atchison's research on pupil diameter and adapting field size, which is used to explain instrument brightness constancy based on a tradeoff with changes in the retinal projection (AFOV) area.

Ed

Thanks for this reference, Ed. Very interesting.

Regarding Table 14.1, shouldn't the corresponding mm values for F -7 and F -10
read something like 13.6 and 13.1 instead of 14.6 and 14.1? Is this a typo?

Tom