I'm afraid your misinterpreted what I wrote, or, I misinterpreted what my brain was thinking. :-)
My reference to the speed of the lens as "or thereabouts" was my saying I am not going to go out to the car and drag the camera case out to look at the lens to see what it's spec. is, nor am I going to hop on over to Boz's site to see if it's listed (it is, I recall). For you, just this once, I will open my spreadsheet inventory and see what I wrote: Pentax SMCP-FA-J 75-300mm ƒ4.5-5.8 ED See. Worse than I recalled. What I was referring to was the total cone of light being (on most lenses other than flat field & macro) sharper in the center than the edges. Therefore, a FF lens on an APS sensor would be using the sharper, cleaner part of the optical circle than the FF camera would. On Sep 26, 2012, at 00:21 , Igor Roshchin wrote: > Tue Sep 25 22:48:50 EDT 2012 > Joseph McAllister wrote: > >> I have the far inferior FA-J 75-300 that came with a FF body last >> year. FF Coverage, of course. I was surprised that it took pretty damn >> good pictures on the K-5. Another of course is that it is only using >> the center of the image, so the best it can give for DA size. It's >> essentially a 105-450mm f3.5-5.6 (or thereabouts) > > Joseph, it is incorrect. There is no "equivalent" aperture of the lens > for a different crop factor if you are talking about the lens ability > to let the light through (aka lens "speed"). > So, each point of the APS sensor will get the same amount of light as > any point on a FF sensor. > > What is affected by the sensor size is DOF (depth of field). Joseph McAllister [email protected] -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
