I don´t know quite how to measure real eye-relief (without sticking a tape-measure in my eyeball
) but I reckon it´s about 15mm, for both the 8x and 10x EII´s. I do wear glasses with my EII´s nowadays, but (and this is going to sound so obvious as to be daft), it depends what glasses. My normal everyday glasses (the ones I wear to work, at home etc.) don´t work with
any binoculars because they sit further out on the bridge of my nose (and I have a big nose). I have special "dedicated" birding-eyeglasses (we had a thread about that some time ago), which are small round wire-framed, and sit back into my eyes. With these, I can get full FOV with my EII´s and my EL´s. It´s been said before, but I think the crucial feature is not the eye-relief of the binoculars, but the eye-relief of the spectacles, that makes the difference. So much so that I´m going to save myself a fortune and
not buy any of these new ED long-er bins (that might never get produced anyway....
).
EDIT: correct the previous gibberish ... (not Sancho's post ... I posted a gibberish response ... copy and paste error!).
Eyeglasses don't have "eye relief". They're like Galilean telescopes in that they don't have an exit pupil. They just add or subtract power the eye lens system (the lens + the cornea).
The important thing is just matching the position of the exit pupil from the back of the eyepiece to the position of the entrance pupil of the eye (after it's been "moved" by any "lenses" placed in front of it like your eyeglass or your cornea).
So eye relief is easy to specify optically ... the distance from the back of the last lens to the position of the exit pupil. Done.
Easy.
Except for the problem of "unusable distance" enforced by the eyecups around the lens. This makes a difference from eyeglass wearers (but not usually for non-eyeglass wearers as their eye doesn't care about that edge). So that removes bit of distance from the "optically correct" ER making some sort of "usable ER".
And then these the problem of the marketers and the "big numbers" sell. So you get the Audubon that quotes IIRC 16mm (sounds good) but with glasses is closer to 12mm usable (not so good ... you will lose field).
Then there's the problem of the glasses themselves. There's a convenient fiction that the vertex distance (the distance from the front most part of the cornea to the back of the eyeglass lens) is 15mm. It actually makes a little difference to the correct prescription but as lenses come in multiple of 0.25 diopter it doesn't show up.
But people fit eyeglasses in all sorts of ways with vertex distances below 10mm (though your eyelashes might start to hit the lens) out to 30mm (big eyeglasses worn down the nose often by old guys!). These difference distances make all the difference.
Then there's how much correction you need and what the eyeglasses are made out of. High index plastics make thinner lenses and so help with poor ER.
You could give a person with close fitting thin lens (10mm vertex distance) a bin with 14mm ER and they'ed see the whole field. Give it to the guywith the 30mm vertex distance and thick CR39 lenese and maybe he'd see a little bit in the middle. Same bin. Same ER. Different eyeglasses and different people.
Add in deep set eyes and you can see the problems.
Sancho (and me) do the right thing by having custom eyeglasses for birding.
But even than can lead to problems ... my nice close fitting glasses give me problems with the SE. Why well one reason is the ER is too long with the eyecup down for my close fit eyeglasses. So I need to move the eyeglasses out.
So getting the balance right is a problem ... and the only way to know is to test. But you can stack the deck in your direction with well though out birding eyeglasses.