Only 2. Dave
On Sat, Apr 4, 2009 at 11:01 AM, William Robb <war...@gmail.com> wrote: > In response to this question: > > "I was informed that the camera is a little bit under-exposed, but I want to > know how much. That is, if I set the EV compensation, but how much (1/3? > 1/2?) should I set so that I can get normal exposure?" > > This answer was given: > > "Well, regarding the exposure problem, let's say it's related to the lens > used. > For f/3.5-5.6 lens, exposure will be quite good. > But with fast lenses, you'll have a variable amount of underexposure... > - f/1.4 needs about +1 1/2ev > - f/2.8 needs about +1ev > > and so on... > > This is due to the fact that the focus screen does not respond in a linear > way to the aperture of the lens... > You should have a direct relation between shutter speed and aperture (i.e. > going from f/1.4 to f/2 should halve the shutter speed, going from say > 1/1000 to 1/500). > But with the original k20 focus screen, this relation is not respected > (going from f/1.4 to f/2 won't halve the speed). > > Note : I'm talking about using actual, stop-down apertures. > > For A lenses, the exposure is mesured wide-open, then calculated for the > given aperture you want to use, so selecting f/2 will always gives half the > speed of f/1.4. > BUT the wide-open reading will be underexposed by the 1 1/2ev mentionned > above, so the lens will always underexpose, whatever aperture you're using. > > Using an old lens (with aperture blades actually moving when you select an > aperture on the lens), you'll see that closing one stop won't halve the > speed. > > You can lessen this behavior by using a LL60 screen (from the *ist line). > They are fully compatible with the k10/k20, and lessen the discrepancies to > the point where you won't really need to compensate the exposure anymore." > > -------------------------------------------- > > I'm not seeing where the answer could possibly be correct, but I thought I'd > post the whole thing here, hoping to generate some discussion. > This comes from that forum thang, where I managed to get a 2 point demerit > yesterday for telling a guy to fuck off. > Godders, I must just have been having a shitty day yesterday... > > William Robb > > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and > follow the directions. > -- Equine Photography www.caughtinmotion.com http://brooksinthecountry.blogspot.com/ Ontario Canada -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
