Archived posting to the Leica Users Group, 2013/10/03
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I like the shot. I guess I like all cat shots; I'm a cat nut. Obviously the exposure value was determined by the books. What was the argument? Herbert Kanner kanner at acm.org 650-326-8204 Question authority and the authorities will question you. On Oct 3, 2013, at 4:25 AM, Sonny Carter <sonc.hegr at gmail.com> wrote: > First argument I ever got into in the LUG was over the black cat thing. At > the time, I think I was the only person with a black cat. It depends on > the circumstances. > > http://www.sonc.com/belinna_guards.htm > > > On Thu, Oct 3, 2013 at 1:34 AM, Herbert Kanner <kanner at acm.org> wrote: > >> That's where you use exposure compensation. Shoot a white swan: increase >> exposure by compensation or any automatic system will want it to be gray. >> Shoot a black cat and decrease exposure for same reason. >> >> Herbert Kanner >> kanner at acm.org >> 650-326-8204 >> >> Question authority and the authorities will question you. >> >> >> >> >> On Oct 2, 2013, at 12:00 PM, John McMaster <john at mcmaster.co.nz> wrote: >> >>> I cannot see how it would? There I am putting an exposure in for a >> silhouette and the camera thinks "that's underexposed" so ups the ASA 3 or >> 4 stops.... >>> >>> john >>> >>>> -----Original Message----- >>>> >>>> I'll have to read again, but I don't think AutoISO works on pure manual >>>> mode... >>>> Would you double check also? >>>> Thanks Herb, >>>> Bob >>>> >>>> >>>> On Tue, Oct 1, 2013 at 9:30 PM, Herbert Kanner <kanner at acm.org> >>>> wrote: >>>> >>>>> I thought a few words about how this function operates on Leica, at >>>>> least on the M9, might be useful to y'all, since the Leica Manual is >>>>> not the clearest on this subject. >>>>> >>>>> Let's start with an understanding of the relationship between the >>>>> three >>>>> parameters: ISO, f-number, and shutter speed. We are used to thinking >>>>> of exposure having one degree of freedom for a correct exposure. That >>>>> is because we are used, from years of experience with film, of >>>>> thinking of ISO being a constant. You can't change ISO in the middle >>>>> of a roll of film. So, for any situation, there is one degree of >> freedom for a >>>> "correct" exposure: >>>>> you change shutter speed, you have to change aperture, and vice versa. >>>>> Hence, for the little all-electronic cameras where both the aperture >>>>> and shutter are under computer control, you can choose the aperture >>>>> (aperture preferred), or you can chose the shutter speed (shutter >>>>> speed preferred) and the camera choses the one you didn't chose. You >>>>> all know this; I'm just being pedantic. Oh, then these idiot cameras >>>>> have "programmed" mode where the camera chooses both based on >>>> some arcane set of rules. That's for bozos. >>>>> >>>>> Now, lets look at the Leica. The camera can control the shutter, but >>>>> it can't control the aperture. So the only automatic mode would appear >>>>> to be aperture preferred. Ah, but the ISO is under the control of the >>>>> camera's computer. It is now a third variable: it can be changed at >>>>> any time. So, Leica in its wisdom invented Auto ISO. Now we have two >>>> degrees of freedom. >>>>> That is, we can pick the values of any two: say ISO and aperture, and >>>>> now the shutter speed is determined. Thus, on the Leica, we now have a >>>>> way of doing shutter speed preferred: set the shutter to the speed you >>>>> want, set the aperture to the f-number you want, and the camera will >>>>> pick an ISO that gives the correct exposure. So, what happens if you >>>>> set Auto ISO and aperture preferred on the M9? You will be in s >>>>> situation similar to program mode in a point and shoot. The camera >>>>> will chose both the shutter speed and the ISO value. I took a few >>>>> shots at three consecutive stops on the dial, and the shutter speed >>>>> sat at 1 /150, perhaps not what I would want with a 90mm. >>>>> >>>>> If you set a shutter speed and an f stop with Auto ISO, everything >>>>> works fine as long as the ISO that gives "correct" exposure is in the >>>>> available ISO range. And you can use exposure compensation. What you >>>>> lose is any information about exposure in the viewfinder. What >>>>> information could that be? The ISO the camera selects, of course. >>>>> >>>>> One warning: the little dot and triangles used for manual exposure >>>>> setting seem to be meaningless with Auto ISO: just ignore them. >>>>> >>>>> Herbert Kanner >>>>> kanner at acm.org >>>>> 650-326-8204 >>>>> >>> >>> >>> _______________________________________________ >>> Leica Users Group. >>> See http://leica-users.org/mailman/listinfo/lug for more information >> >> >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information >> > > > > -- > Regards, > > Sonny > http://sonc.com/look/ > Natchitoches, Louisiana > 1714 > Oldest Permanent Settlement in the Louisiana Purchase > > USA > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information