On Jan 4, 2007, at 11:47 AM, Charles Robinson wrote: > On Jan 4, 2007, at 8:51, Godfrey DiGiorgi wrote: > >> >> The one case I have not checked is to use a pre-A lens in Av mode and >> see if that works with P-TTL. It might, because the lens will ALWAYS >> be wide open ... the camera can make the exposure evaluation with the >> pre-flash before lifting the mirror. > > I don't get what you mean by the lens "always" being wide open. > > If you have a smaller aperture selected via the aperture ring, the > lens will stop down when the shutter trips - regardless of whether or > not you've metered for that possibility beforehand. > > Or am I missing something?
You're missing something. With all the Pentax DSLRs, when you use pre-A series (K-mount or Pentax-M) lenses, the iris will only stop down to taking aperture when the camera is in Manual exposure mode. All other exposure modes default to Av, and the iris does not stop down to taking aperture until AFTER the exposure is made in Av mode with these lenses. You can see the iris cycle, it must due to the interlock between mirror and iris actuation mechanisms, but it is cycling after the exposure has already happened. That's why some prefer to use M42 lenses rather than K/M series lenses. M42 lenses must be manually stopped down to taking aperture *prior* to releasing the shutter, so Av mode is more flexible. Godfrey -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
