Archived posting to the Leica Users Group, 2016/02/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Jay: I mentioned this in the other thread that in which Howard's question appeared, but I'll ask you here as well: Do you know why Capture One displays my M8's estimated f-numbers, but not my (MM) Monchrom's? --Peter On Thu, Feb 11, 2016 at 7:51 PM, Jay Burleson <leica at jayburleson.com> wrote: > Top center left on the front of an M body is a small window which contains > a metering cell that meters the environmental light, in order for the > camera to be able to guesstimate the lens aperture. This is relevant for > in-camera vignetting correction as well as EXIF data. > It compares the light coming to it with the value of the max aperture as > reported by the 6-bit coding and comes up with a (sometimes spurious) > number. For example, use of the exposure compensation will really throw it > off. I run -2/3 almost all the time on my MM and it reports to me that my > Summilux wide open is f/1... > > Jay > > On 2/11/2016 5:35 PM, Howard Ritter wrote: > >> Can anyone explain how Lightroom reports an aperture for images made with >> M cameras, which don?t have a way to report their aperture setting to the >> camera? All the camera knows is what the lens?s maximum aperture is, as >> reported by the 6-bit code or manually. >> >> I just ran off a series of images with a coded 24/2.8, one at each usual >> stop from 2.8 to 16. LR reports the apertures as 2.8, 3.4, 4.8, 6.8, 9.5, >> and 13. The aperture could be inferred from the integrated light >> intensity, >> but only if the camera knows the intensity of the illumination of the >> subject, which of course it doesn?t. I?m puzzled not only by the fact that >> LR reports an aperture setting, which the camera has no means of knowing, >> but even more by the fact that the values are different for each exposure, >> increasing continuously in the right direction, and most of all by the >> fact >> that the values are, as Tina says, in the ball park. And the Mac?s Preview >> app reports an Aperture Value, which for the same sequence of images also >> increases correctly, but ranges from 2.97 to 7.4. >> >> With a non-coded 35/1.4 and lens data entered manually, LR reports the >> apertures as 1.4, 2, 2.8, 4, 4.8, 8, 9.5, and then drops to 4 for f/22. >> Preview does much the same thing but less accurately, reporting a >> progression from 0.97 to 6.5, but then dropping to 6 for f/22. >> >> With the same non-coded lens, but the lens data manually entered >> incorrectly as 90/2, LR gave the apertures as 2, 2, 2.8, 4.8, 5.6, 8, 9.5, >> and 4. Preview gave them as 2, 2, 2.97, 4.5, 4.96, 6, 6.49, 4. >> >> I am completely baffled. Anyone have an answer? How do the programs >> derive a value for f/stop? Since LR and Preview report different apertures >> for the same exposure, it can?t be just information supplied by the >> camera. >> The camera knows what the maximum aperture of each lens is, but what, the >> camera or the program, or both, decides that a lens is set to that, or to >> anything smaller? >> >> ?howard >> > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information