Archived posting to the Leica Users Group, 2009/01/15
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Steve I think that there are several issues confused there. The original linear information captured must be conform to the fundamental principle. Half of total are used the represent the first (brightest) stop, one quarter the next, one eighth the next, one sixteenth the next etc. Up to a reported 81/2 stops of maximum dynamic range for the DNG. Picking an easy example because the maths makes my brain hurt, -1 exposure compensation will mean you are halving the number of possible tones you capture. What ever total tonal range you do capture is shifted (tones greatly redistributed) by using a gamma curve since we don't see light in a linear fashion like sensors do. Since we are much more sensitive to tonal differences in shadows than highlights that shift works out OK but you still have vastly less tones in the darkest stop than the brightest. That all applies to any digital capture BUT then the M8 throws in a complication. The camera takes the original 16 bit capture, (actually throws away the two lowest bits which are too noise contaminated to be useful) and uses some more maths to represent those 16 bits as 8 bits. But the original information is reconstructed from that when you open the file in your DNG convertor. That compression process, Leica tells us is nearly lossless for practical purposes but gives us smaller files to manage in the camera (10MB vs. 20MB). That is NOT the same as just capturing as jpg in the first place. Of course if you are capturing as jpg then you are only getting 8 bit, you've lost the rest of the information permanently. Now absolutely no argument from me that routinely underexposing may well be a practical technique and lots of M8 shooters more experienced than I, use it happily. Not doing that is my personal technique to extract the most possible information from the M8 files. After all, its dynamic range is one of the features that makes it a standout against mere mortal dSLRs! Ps, I haven't changed anyone's opinion have I ?? ;-) Cheers Geoff http://www.pbase.com/hoppyman/e http://gallery.leica-users.org/v/gh/ Pick up your camera and make the best photo you can. -----Original Message----- Subject: Re: [Leica] Question about M8 exposure The M8 doesn't assign the 'bits' in a linear fashion. More of them are assigned to the shadow end of the spectrum than the highlights. Steve On 15/1/09 19:34, "Bob W" <leica@web-options.com> wrote: > if you shoot RAW you lose a lot of information that way which could be > useful during post-processing. You significantly reduce the dynamic > range you have available. _______________________________________________ Leica Users Group. See http://leica-users.org/mailman/listinfo/lug for more information