Seems an obvious question to me. By way of analogy, some camera lenses are faster than others, and in an application where a faster eyepiece would mean coaxing dimmer objects into visibility you would have thought it was an important spec.
Similarly, with camera lenses the best quality in terms of resolution and contrast comes from primes, not zooms. So I'm curious as to why zoom eyepieces are a thing?
Not 'casting Nasturtiums'
at people who like them, just wondering why these things that are true for camera lenses don't seem to apply to EP'S?
And in any case, for things like the speed of an EP, or contrast, resolution, even the shape of the focal plane as pointed out by Alexander - these things are surely objectively measurable in the same way that camera lenses can be tested?
And lastly, why are EP'S with more elements considered better? If each air/glass boundary represents possible light loss isn't that a liability? And given that each lens is built to a tolerance, shouldn't more lenses lead to more variability in the quality of that design?
Not wanting to ruffle feathers here, just curious as to why things that apply to camera lenses dont apply to EP's and why this stuff doesn't form part of the spec sheets.
Markus