When comparing the speed of two lenses, you almost exclusively hear about the maximum aperture. This of course makes sense, since at a certain lighting condition, a larger aperture in general allows a faster shutter speed.
But is this really the whole story? I guess the relevant property to compare is the amount of light actually hitting the sensor when the lens is wide open. Therefore, the transmission of the lenses should be important to include in the comparison.
- How much does the transmission in today's lenses affect the overall exposure?
- Does the transmission differ much between primes, which generally have simpler structure, and zoom lenses, which are more complicated.
- How much does the massive coating of modern lenses affect the transmission measured in Ev?
- Is the transmission of lenses revealed by the manufacturers?
For example, a 35/2 prime is only a third f-stop slower than a 18-35/1.8 zoom. Can the difference in transmission make the prime "effectively faster" although it has a smaller aperture? (Of course it can theoretically, I mean practically with modern lenses.)