In a message dated 12/5/01 8:53:28 AM Eastern Standard Time, [EMAIL PROTECTED] writes:
> Subj:Re: Variable aperture zoom question > > (Hi, > > Fred wrote: > > > > Mike: > > > > > Suppose I have a variable aperture zoom lens, say 28-80mm > > > f3.5-f5.6 If I set the zoom at 28mm, and set the aperture wide > > > open, it should be f3.5. If I then zoom to 80mm, the effective > > > aperture goes down to f5.6, right? And if I zoom to 50mm, the > > > aperture will be somewhere in between, say f4 maybe. > > > > Right. > > Right. > > > > Now suppose I set my zoom to 50mm @ f8. > > That's not an easy task. The aperture markings usually correspond to > the widest aperture. So, if you set the focal length to 50 and the > perture ring to where "8" is marked, you will have f/8 @ 28 and > something like f/13.5 @ 80 mm. > > > > If I zoom out to 28mm, will the effective aperture stay at f8? > > > If I zoom in to 80mm, will the effective aperture stay at f8? > > > Nope, in both cases (although my understanding is that the relative > differences in aperture at different focal lengths diminish as one moves > away from "wide open"). > > If you did manage to set exactly f/8 @ 50 mm, the answer is no to both > questions. > > > In any event, if you're using TTL metering (which most of us use most of > the time), then the exposure recommendation should automatically compensate > for the variable aperture problem. > > This is, fo course, correct and the most important thing. The trouble > with the variable apertures comes in play when you use manual flash, > studio flash, etc.) > > Cheers, > Boz _____________________________________________________ Pardon me if I misunderstand the gist of you response: the operative question asked by Mike was : "if I set"... Are you (anyone) now suggesting that setting the aperture manually, somehow changes the aperture as you zoom? How? ***Taking the aperture ring off "A" makes it a ~manual~ lens, or are you (anyone) saying that somehow, the camera/lens changes what is a (preset) aperture anyway? How? Mafud [EMAIL PROTECTED] [EMAIL PROTECTED] - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
