Thanks for all the responses. With respect to the difference between K and A (and later) lenses, linear diaphragm actuator, etc, I think description on the KMP (Boz Dimitrov's) page is simple and clear: http://kmp.bdimitrov.de/technology/K-mount/Ka.html My question was about a different thing.
Godfrey and Walt: I was thinking this way: since it is possible to do exposure variation in 1/2 or 1/3 EV steps (especially in Tv), the camera should be able to relay this into the aperture steps. I am glad to hear that it is the case (as seen in the metadata), as in principle, it does not have to be the case: even though ISO numbers are defined in 1/3-stop increments, I suspect, in the TAv mode on k10D, the ISO cannot be changed in 1/3 EV steps, can it? (and 1/2 EV steps are out of the question as well). On another hand, if indeed, the aperture can be varied in 1/2 and 1/3 f-stops (EV steps), this means that either the camera is capable of handling at least aperture steps equivalent to 1/6 EV (to be able to do 1/2 and 1/3 variation from any aperture setting), or it may be able to do 1/2 or 1/3 _variations_ from any 1/2 or 1/3 EV step, but not being able to address some of those settings directly (i.e. you cannot set f/4 + 1/6 EV, unless you are in 3-shot variation shutter mode). It is, however, possible, that the camera is approximating to the setting that is nearest to 1/2 EV or 1/3EV away from the current. This article http://en.wikipedia.org/wiki/F-number#Fractional_stops claims that Canon DSLRs use 1/8-stop increments and does the approximation for the 1/3 and 1/2 EV steps. Sorry for going into deep technical details. I am just curious how things work. Igor -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
