Advantages of good Eye Relief

[APSmith]

Most commentary on eye relief seems to center around the eyeglasses question. I do not wear eyeglasses, but still find a couple of real advantages to good eye relief:

Lesser tendency for condensation on eyepiece - Bins I've used with longer eye relief allow noticeably better ventilation between the lens and eye/face, and therefore less condensation problems. This is especially true when I leave the eyecups down and space the bins off of my face with my brow or thumbs.

Easier to look "up" - When viewing high in the trees for longer periods, I commonly put the eyecups all the way down, and rest the tops of them higher than usual against my brow, in order to lessen the degree to which I must tilt my head back. (I can then look up with my eyes instead of just my head/neck.) The extent to which this can be done without loss of FOV depends on the amount of ER.

In the field, these advantages have made a big difference for me in certain situations. Have others noticed this?

It's just another consideration (even if you don't wear eyeglasses) for making a binocular selection.

APS

[Tero]

Besides optics, eye relief and eye cup comfort are major factors for me. I am selling a pair of porros as I no loger like to hold them much.

[Lewie]

I wear glasses, and for me good eye relief is the most important point with binoculars, more important that quality of optics or weight or anything else. Personally, the best optics are worthless if after finding a bird I have to take off my glasses to use binoculars. Using bins with poor eye relieve takes absolutely all the fun out of birdwatching, at least for me.

Lew

[statestat]

I wear glasses, and for me good eye relief is the most important point with binoculars, more important that quality of optics or weight or anything else. Personally, the best optics are worthless if after finding a bird I have to take off my glasses to use binoculars. Using bins with poor eye relieve takes absolutely all the fun out of birdwatching, at least for me.

Lew

I totally agree that eye relief is the top detemning factor, since if you can not see through the bino well all the best coatings and glass are useless. I would propose another important reason for good eye relief not usually mentioned and that is when sharing binos(somehting I do not like too much but it happens). If my mom is with me she need the plenty of eye relief to see anything.

[etc]

Interesting points made.

[Swedpat]

APS,

As you mention a good eye relief is an advantage even without eyeglasses. It's comfortable to not need to press the eyes hard to the eyecups to see the entire FOV. Then we have one forgotten reason for a long ER: if you don't usually wear eyeglasses you can use the binocular with sunglasses on!

Regards, Patric

[ScoutMan]

What constitues "good " eye relief? My Yosemites 6x30 have 20mm of eye relief which I consider outstanding. How low can you go? Maybe 15 mm.

[Phil Bishop]

What constitues "good " eye relief? My Yosemites 6x30 have 20mm of eye relief which I consider outstanding. How low can you go? Maybe 15 mm.

Much depends on the design of the eyepiece.
Many of the very old two or three element designs have very poor eye relief, as low as 20%, but more typically 40% of the focal length of the eyepiece. The few binocular eyepieces I have measured have focal lengths of between 18 and 25mm (this was with some cheap models from the 70's. but I guess the modern ones are similar), and being rather simple designs, have eye reliefs of around 8 to a just about tolerable 14mm.
With many of the modern eyepiece designs, eye relief is designed to be constant, often around the 20mm mark, even with very short focal lengths which has been a god send to spectacle wearers like myself.

[lvwally]

I can think of one more good reason to shop for a bin with good eye relief -- and that is, I can remember a time when my eyes were perfect... then I turned 40. Suddenly the newspaper crept further and further away in the morning, and soon after came the reading glasses. Next came the distance glasses.

Quality binoculars can last a lot longer than perfect vision. All of you for whom eye relief is not an issue -- it is not an issue NOW. I hope you can still use those favorite bins when you are past your prime.

Wally

[Swedpat]

My experience is following:
About the eye relief you have take the numbers "with a pinch of salt" and try before you by.

Also the important thing isn't how long the theoretical eye relief is, but the usable. In many binoculars, the eyepiece lens is recessed several millimeters more from the eye cup edge than necessary, resulting in that you can't make use of the actual eye relief. The stated eye relief of the Yosemite 6x30 is 20mm which works well with eyeglasses. Swarovski SLC 7x42 has stated 19mm eye relief, but works even better with eyeglasses. One reason is that the recessment of the eyepiece lens is minimal with the eyecups in the lowest setting.

Regards, Patric

[Fernando np]

In riflescopes, ER are specially important. When I was working as hunting guide, several times it was necessary to go to see the doctor for sewing eyebrows of hunters. The backwards movements of the scope in the shooting can make a lot of blood when the gun isn't properly fixed. If the hunter becames feared of his gun the danger for fauna at long range will be almost nil. One solution is to do bigger the distance among eye and scope. So is easy to find very long ER, specially in big calibers. You change ER for FOV. I don't know if also light transmission. US Optics offers among the accesories the option of a 4" ER. Its webpage, usoptics, doesn't run in this moment for linking.

[iporali]

Excellent comments, but obviously long ER has its side effects too. ;)

I wear glasses and I do need relatively good eye-relief. I also digiscope and report time after time about the importance of ER when combining the camera and the eyepiece. But... I am also one of those who are repeatedly reminded (and annoyed) of too "good" ER.

1. As Fernando mentioned, the ER and apparent FOV are mutually exclusive properties if the diameter of the eyelens stays constant. Sometimes I would like to trade that ER beyond 16mm to slightly more AFOV.

2. Long ER and wide FOV increase the tendency for blackouts. If the eye pupil is small (as in bright light) and too close (due to long ER), a bean-shaped black shadow floats around in the FOV.

3. Long ER requires very good adjustable eyecups for those who don't need all that eye-relief. The longer the ER, the floppier the eyecups often are fully extended. The blackout tendency of the Nikon SEs is IMO not because of the ER or "spherical aberration of the exit pupil" (SAEP), but because of too thin, short and unadjustable rubber eyecups, which don't give enough support.

4. More stray light... well, with most eyecup designs.

So there are trade-offs in long ER for some users, but generally, yes, long ER offers many advantages and is often the feature that separates great binoculars from good binoculars.

Best regards,

Ilkka

[NWBirder]

Be careful to watch out for some binoculars that have eyecups that do not match with the eye relief spec. For example, the eye relief is labeled as 20mm. The eyecups only go up for 12mm. It means you cannot push your eyes against the eyecups to block any stray light from coming in.

[Swedpat]

Long eye relief is seldom a problem according to my experience. Suitable eyecups makes it possible to adjust the distance to the correct level. Short eye relief is worse, because it cannot be measured.

Regards, Patric

[etc]

Be careful to watch out for some binoculars that have eyecups that do not match with the eye relief spec. For example, the eye relief is labeled as 20mm. The eyecups only go up for 12mm. It means you cannot push your eyes against the eyecups to block any stray light from coming in.

That's exactly the problem with Swaro EL 8.5x42. The eye relief is great, but the eyecups don't accomodate it. I had to install eyecups from Swaro SLC 8x50.