I think where I am confused is that beyond the twilight factor there are other factors in light transmission that are not listed and hard to find any information on other than add copies and subjective opinions. Things such as individual light transmission, reflectivity, interior glare reduction, type of lens glass, size of lenses and housing, coating types, dispersion, edge aberration, etc. etc.
Can't these things be measured objectively with something as simple as a light meter and a test pattern? I was also looking for a ranking of light transmission for similar sized scopes, especially the smaller to mid sized ones. I know that any of the better mid range scopes would work well within legal shooting time.
Unfortunately it's not as easy as just using a light meter and using light transmission to judge scope quality. You can look through an empty toilet paper roll and get 100% light transmission but it's not going to help you see to shoot better! A brightly lit unresolved blob is still an unresolved blob. Some scopes use an extra lens to help sharpen and refine the overall image. It won't be as purely bright as a scope without it but the image will be better.
Also scopes with different coatings transmit light at different wavelengths in different amounts. The trickiest thing about this is that different people see into different wavelenghts better or worse than others.
In the end the very best way to see which scope has the best optics is to look at it side by side with the other ones you are comparing it to, preferably in low light. The more expensive scopes usually are better overall but to get a little bit better optics you have to pay a lot more money......................DJ
