Albertabirder
Active member
Just wanted to clarify how eye relief is measured, is it the distance that the eyecup moves out from the body? Thanks
Michael
Michael
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Clarify how eye relief is measured???? (1 Viewer)
- Thread starter Albertabirder
- Start date
Michael,
If you point the binocular or scope at a diffuse light source (sky?) you should be able to focus a sharp image of the exit pupil on a ground glass screen. The eye relief is the distance from the eye lens of the ocular to the ground glass, and the effective eye relief is from the retracted eyecup to the ground glass.
John
If you point the binocular or scope at a diffuse light source (sky?) you should be able to focus a sharp image of the exit pupil on a ground glass screen. The eye relief is the distance from the eye lens of the ocular to the ground glass, and the effective eye relief is from the retracted eyecup to the ground glass.
John
Albertabirder
Active member
No, the eye relief is an optical property, not a mechanical one. The exit pupil is outside the eye lens and the adjustable eyecups are there to facilitate eye placement. If you get too close you are going to experience black-outs or kidney-beaning, too far and you are going to lose some field of view.
John
Alexis Powell
Natural history enthusiast
Eye relief is from ocular lens to the distance your eye has to be to see the full field comfortably. As Tringa45 noted, the eyecup is simply there to assist in that positioning, it has no effect on eye relief. If you wear glasses, the glasses lens can interact and change the eye-relief (e.g. myopia prescriptions allow the eye to be slightly farther from the ocular lens). Manufacturers usually list eye-relief based on measurements according to the definition above, but a few measure from the top of the retracted eyecup instead of from the ocular lens.
--AP
--AP
Albertabirder
Active member
Thanks for clearing this up for me, it seems for my eye structure I suffer from blk-outs on all optics I have owned over the years, for me the further away from the eyepiece ocular the better, the pic shown is the STX and it has as you can see not a lot of movement in the eyecup adjustment, I suppose I will just have to live with it, just recently purchased NL's 10x42 w/FHR and finding out that the rest and the good range of eye-cup adjustment really helps me find the sweet spot and maintaining it. Thanks, learning all the time on this site....Michael
