On Jul 5, 2006, at 5:38 AM, Don Sanderson wrote: > 1.) With film you "expose for the shadows and develop for the > highlights". > 2.) With digital you "expose for the highlights and develop for the > shadows". > > (Please note that the word "important" should always appear before the > words "shadows" and "highlights".)
Fundamentally correct as a rule of thumb, if by film you mean *negative* film. > Number 1 is a basic rule of the "Zone System" _for film_. For *negative* film. For transparencies, you place the highlights and develop for the shadows. > Number 2 is a basic rule for digital _jpegs_, but is rather > misleading. > Digital _RAW_ falls in between the two, but is more like number 1. Um no, your expression is misleading on both counts. A digital sensor operates the same whether you are saving the capture as RAW or JPEG format (see my previous post in this thread for a detailed explanation... ). The differences between them in terms of exposure evaluation is that JPEG format ends up leaving you less data in the stored file and has a smaller range of editing robustness after the fact. It reduces the total dynamic range you have to work with and requires that you evaluate exposure to accommodate that characteristic at the time of capture. IOW, The basic idea of how to evaluate exposure for JPEG and RAW is the same. You just have less to work with using JPEG captures that must be accommodated. > Jpegs are 8 bit, processed by the in camera software, and are > pretty much > a done deal. They leave little or no room for post processing without > actually (substantially) degrading the image tonality. Much like > slide film, you can > vary ONLY exposure (and contrast) to achieve final image tonality. Not quite true, but what's true is that you have only 256 numbers per channel in editing resolution. This means that 8bit JPEG files are "fragile" with regard to editing capabilities. > 12bit RAW files on the other hand are more like a negative, a great > deal of post work can be done, as a matter of fact must be done, to > achieve a final image. > With negative film you can vary both exposure AND development time. > You can do something quite similar in a RAW convertor, many highlights > can be recovered at this stage. > > I no longer compare "digital" to negatives or slides. > I now compare "jpegs" to slide film. > and compare "RAW" to negative film. This is incorrect insomuch as both JPEG and RAW require the same exposure evaluation strategy due to the fact that both are dependent upon the characteristics of the recording medium. RAW format both requires and allows greater flexibility in post processing due to the greater dynamic range, in turn due to the larger set of numbers used to represent the image, and the flexibility possible by customizing the gamma conversion and chroma interpolation curves. But the principles of proper exposure are the same for both. Godfrey -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
