Joseph, Sorry, - I thought you were trying to calculate the "equivalent" aperture, while you just didn't quite remember what the aperture was. (And I was not talking about the "equivalent focal length")
Thanks for the clarification. Igor Wed Sep 26 03:56:35 EDT 2012 Joseph McAllister wrote: > 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 f4.5-5.8 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). -- 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.
