Does anyone have a reasonable approximation of the transmission efficiency of modern binoculars? In the 1950s it was said that the total efficiency was about 50%±, meaning that only that much of what went into the objective came out the exit pupil. The rest messed up the contrast of the image. Nowadays the manufacturer's talk about 99.5± efficiency, but I don't know if that refers to total throughput or transmission at each internal surface.
Basically, for Porros and roofs, I'm trying to get a ballpark transmission for binocs with: (1) uncoated lenses (2) partially coated (3) fully coated and (4) phase corrected (for roof's only).
Without additional information I'm inclined to make WILD guesses. Any source of such information would be greatly appreciated.
Thanks,
Elkcub
99.5-99.8% refers to maximum transmission at one glass-to-air surface using the very best multi-coating. The loss is 1-1.5% per surface for single layer MgFl coating, 5% for uncoated glass. There are 10 to 18 or more surfaces in binoculars. Then there is loss from prism reflections. Loss in transmission through about 100-130mm of solid glass. Loss caused by vignetting from under sized prisms and prism aperture stops. Greater loss at the higher wavelengths to which the eye is most sensitive in very low light. Judging from figures that have been posted on this forum (Kimmo posted the results of a Finnish test report on the Canon IS subforum) the range of transmission from the worst to the best modern binoculars is probably from below 60% to above 90%.
Gentlemen:
I have read, several places over the past 6 or 7 years that the best Fujinons with EBC coatings pass more than 95% of the light, which is considered the best in the industry!! This technology is a few years old. Todays technology, may be better. I hope!
(I'm speaking of the entire binocular, not just one lens.)