Yes, all else being equal, and I'm thinking specifically about coatings and glass formulation and quality. But you're right. I've also seen the difference between certain primes. I was originally puzzled by the different meter readings I got when using the K85/18 and a couple of other lenses (later models with different coatings). on the same subjects. The readings showed the K85/1.8 was almost a stop slower than the newer lenses with better coatings and probably different glass formulations.
I wonder how many people when using the camera's built in meter notice small metering differences, especially these days where the lenses get set automatically. All of my cameras, until the DS, required that I actually adjust the exposure in some way, so I was very much aware of what was happening with the metering, whether using the camera's meter or a hand held meter. This is a reason why cinematographers use, or used, T stops. Shel > [Original Message] > From: graywolf > > Primes simply transmit more light. Each piece of glass in a lens absorbs > some light, as do each air/glass interface (although air/glass losses > are reduced by modern multi-coatings) So a Prime (f/2.8) with 4 elements > and 6 air/glass surfaces will transmit more light than the same f-stop > zoom with 10 elements and maybe 13 air/glass surfaces. The f-stops are > the same the T-stops (transmission-stops) are far different. The zoom is > likely to lose a whole stop compared to the prime. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
