Editing Binoculars (section)

=== Eye relief ===
[[Eye relief]] is the distance from the rear eyepiece lens to the exit pupil or eye point.<ref>"Introduction to Optics 2nd ed"., pp.141–142, Pedrotti & Pedrotti, Prentice-Hall 1993</ref> It is the distance the observer must position his or her eye behind the eyepiece in order to see an unvignetted image. The longer the focal length of the eyepiece, the greater the potential eye relief. Binoculars may have eye relief ranging from a few millimeters to 25 mm or more. Eye relief can be particularly important for eyeglasses wearers. The eye of an eyeglasses wearer is typically farther from the eye piece which necessitates a longer eye relief in order to avoid vignetting and, in the extreme cases, to conserve the entire field of view. Binoculars with short eye relief can also be hard to use in instances where it is difficult to hold them steady.

Eyeglasses wearers who intend to wear their glasses when using binoculars should look for binoculars with an eye relief that is long enough so that their eyes are not behind the point of focus (also called the eyepoint). Else, their glasses will occupy the space where their eyes should be. Generally, an eye relief over 16 mm should be adequate for any eyeglass wearer. However, if glasses frames are thicker and so significantly protrude from the face, an eye relief over 17 mm should be considered. Eyeglasses wearers should also look for binoculars with twist-up eye cups that ideally have multiple settings, so they can be partially or fully retracted to adjust eye relief to individual ergonomic preferences.<ref>{{Cite web |date=2022-04-19 |title=Birdwatching Binoculars For Eyeglass Wearers - Best for 2022 |url=https://birdsatfirstsight.com/ |url-status=live |access-date=2022-09-28 |website=Birds At First Sight |language=en-US |archive-date=2022-09-28 |archive-url=https://web.archive.org/web/20220928004247/https://birdsatfirstsight.com/ }}</ref>