More on eyecups. Small exit pupil and large eyecups.
These days I’m trying the Canon IS 8x20, that have a meager exit pupil of 2,5 mm, by most accounts this should make for a finicky eye position and a lower level of ease of view and viewing comfort, as it’s sometimes the case with 8x20 binoculars (mostly pocket binoculars). However, and this is just a personal perception (no intention to pontificate here, just telling a personal experience), the eyecups make all the difference.
The Canon IS 8x20 is an “odd” 8x20, in that it’s not intended as a pocket device, like many other sharing that objective diameter and magnification. Being an IS device, the electronic bits take some space, and the resulting size/shape and weight fit basically within the “compact” category (8x32). And then there’s the eyecups. The shape and size have been criticized, and honestly I don’t think Canon did a terrific job there. However, they do have one positive feature, they’re basically as wide as the eyecups on the 12x36 Canon IS III, and in “full size" binoculars territory.
The inner diameter of the Canon IS 8x20 is approx. 34 mm, while the Canon IS III 12x36 are approx. 35 mm. As you can see in the following image, despite the huge difference in objective size, 20 mm vs 36 mm (this is a whooping difference in area of 3,14 cm2 vs 10,18 cm2), the eyecups share a very similar diameter.
And here's the Canon IS 8x20 compared to the Swarovksi EL SV 8x32, that has some of my favourite eyecups in size and design. The inner diameter of the eyecups on the small Canon is actually larger than the EL, and in fact larger than some "full size" binoculars.
And what has been the outcome of these oversized eyecups (for such tiny objectives) in my case? A striking one: in spite of the small exit pupil, these binoculars work almost as any other “regular” binoculars. So, in my personal experience, it’s not about the exit pupil size, it’s about the eyecups! I’ve used some 8x20 or 8x25 with narrow eyecups (and double hinge, to make things worse), and the result was a very compromised level of comfort and lack of ease of view. On the other hand, I remember some binoculars with low magnification and big exit pupils, that theoretically should have given me a relaxed an easy view, but that was not the case. I can think of the Optolyth NG 7x42, that with a 6 mm exit pupil and low magnification proved to be finicky when it came to eye position and prone to blackouts: it had some pretty narrow eyecups. The 7x35 Leica Retrovid wasn’t that bad, but the eyecup size was the deal-breaker for me. I loved the view, but couldn't use them comfortably. I sold them.
So, in my case (again, not saying this is any universal truth, just a personal experience):
Big exit pupil + small eyecups: Compromised comfort. Won't work.
Small exit pupil + regular eyecups: Acceptable to "normal" level of comfort. Will work.
Small exit pupil + small eyecups: recipe for disaster.
I know that this is, to a certain extent, an oversimplification, and that there’s a lot more to ease of view and comfort than eyecup diameter, but this has been my experience so far and I find it interesting to share it, as well as learning from others' experiences. The two small exit pupil binoculars that I have that display large eyecups and single hinge (Nikon 7x20 CF III and Canon IS 8x20) offer a reasonable level of comfort and can be used for long periods of time without much compromise. The Canon have IS, which could be one reason they work well, but the Nikon don't, and they're also reasonably comfortable. On the other end of the scale, the other small exit pupil binoculars that I have (Leica Ultravid 8x20 and Swarovski Habicht 8x20; already on its way to a new owner’s home) that have small eyecups and double hinge have proven too big a compromise for me in terms of eye positioning and viewing comfort.
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