Archived posting to the Leica Users Group, 2006/09/20
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Thanks Rob. I have learnt a lot, especially from revisiting some of the links, however it's unfortunate that the thread became emotive and unpleasant. From my perspective the whole issue arose from different interpretations of Doug's initial post. I understood what he said and it made and makes perfect sense to me. Others disagreed. Only at the very end of a rather strident and noisy thread, did I finally figure out why two sides seemed to be advocating the same thing "expose to the right" while otherwise apparently disagreeing when the other said the same thing. Then it went downhill. I hope that Doug chooses to rejoin the group at some point. I consider him to be an accomplished and knowledgeable photographer as well as active and helpful LUG contributor. The LUG is poorer for his absence, in my view. Cheers Hoppy -----Original Message----- From: lug-bounces+hoppyman=bigpond.net.au@leica-users.org [mailto:lug-bounces+hoppyman=bigpond.net.au@leica-users.org] On Behalf Of Robert Schneider Sent: Wednesday, 20 September 2006 23:44 To: Leica Users Group Subject: [Leica] Re: "the dynamic range of digital" Hoppy, Granted, I'm assuming that the engineers at Adobe knows something about the software they design and the raw material that software is supposed to work with. In addition, I'm assuming that not even the world-class electrical engineers at Leica have figured out how to overcome the laws of physics. I may be wrong on both counts, but here is a whitepaper published by Adobe on RAW capture and linear gamma. In particular, read the first two paragraphs on page three: Linear capture You may be tempted to underexpose images to avoid blowing out the highlights, but if you do, you're wasting a lot of the bits the camera can capture, and you're running a significant risk of introducing noise in the midtones and shadows. If you underexpose in an attempt to hold highlight detail, and then find that you have to open up the shadows in the raw conversion, you have to spread those 64 levels in the darkest stop over a wider tonal range, which exaggerates noise and invites posterization. Correct exposure is at least as important with digital capture as it is with film, but in the digital realm, correct exposure means keeping the highlights as close as possible to blowing out, without actually doing so. Some photographers refer to this concept as "Expose to the Right" because you want to make sure that your highlights fall as close to the right side of the histogram as possible. HTH, Rob Hoppy wrote: Date: Tue Sep 19 21:26:38 2006 Robert, I understand the linear part and the 50% of tones within the first (brightest) stop. I don't follow why UNDER exposure causes loss in that stop. Isn't the underexpose method meant to preserve as many of those tones as possible? Then you are going to adjust your tonal range after capture so that the 256 possible are chosen from the ones you have captured. In other words, a nice smooth histogram with no gaps after you manipulate the image. I think this is the key point not being considered and resulting in the polarised viewpoints. Not what the file will look like un-altered afterwards to compensate for the underexposure, but how many tones you have captured. If a "normal" exposure results in clipping say half of the brightest f stop approaching 255, aren't you losing far more tones than clipping half a stop from the bottom approaching 0? There must be something I am missing here, and I really want to understand. Cheers Hoppy ______________________________________ Robert Schneider Photography Lexington, MA 781.646.5525 (office) 617.777.2139 (mobile) rob@robertschneider.com www.robertschneider.com www.schneiderpix.com _______________________________________________ Leica Users Group. See http://leica-users.org/mailman/listinfo/lug for more information