A few ways around that data loss: - Use 16-bit gamma RGB. There's still *some* data manipulation in terms of quantizing (rounding up/down), but 12-bit linear has less gradations in all areas than 16-bit gamma.
- Keep all images 16-bit linear and use color-management during any processing to gamma-correct for viewing. Only convert to gamma-corrected images for "prints"... web, etc. The master RGB image stays in 16-bits. -Cory On Sun, 7 Jan 2007, Godfrey DiGiorgi wrote: > Remember that in doing RAW conversion you are performing a gamma > correction on a linear dataset. This means compressing (pushing > closer together, setting the white point on...) the high values) > while expanding (stretching apart, setting the black point on...) the > low values to fit the range of what you've captured to the > characteristic curve of human vision. You also set the gamma and > inflection point of the curve (brightness and contrast). > > While both ends of the spectrum lose some data in the course of doing > this, there is far more data to work with at the high end of the > scale than at the low end of the scale if you've made a correct > exposure for the linear gamma sensitivity curve of a digital sensor. > Setting the black point too early can throw away an excess of data, > for which there is no recovery post RAW conversion. For this reason > it is suggested that you set white point, then gamma and inflection, > and then very carefully black point. While the three are *mostly* > independent of ordering, and "whatever works well" is indeed best, I > find it better to work in this order and iterate through the settings > a couple of times in small moves rather than make large adjustments > all at once. > > You can always adjust the black point further in RGB space using > curves or levels adjustments, I generally prefer to preserve a little > excess data in the dark regions and make the final adjustments there. > > Godfrey > > On Jan 7, 2007, at 4:54 AM, Paul Stenquist wrote: > >> I sometimes set the black point first as well. I'm not really >> conscious >> of a specific ordering of steps in regard to exposure, brightness and >> shadows. I think I vary my sequence in respect to the specific >> needs of >> the shot I'm working with. >> Paul >> On Jan 7, 2007, at 7:03 AM, Jan van Wijk wrote: >> >>> I agree with Tim on this one. >>> >>> Otherwise, I must say Paul's description is >>> pretty close to what I usually do :-) >>> >>> I have developed my RAW workflow based on CS1 experience >>> and Bruce Frasers "Real World Camera Raw ..." book. >>> >>> Working with CS2/Bridge now, and will consider LightRoom >>> once it it released, or perhaps CS3 ... >>> >>>> >>>> But unlike you, I think it is better setting the darks before >>>> brightness. If >>>> I set darkness before brightness, it seems I always need to go back >>>> again. >>>> > > -- ************************************************************************* * Cory Papenfuss, Ph.D., PPSEL-IA * * Electrical Engineering * * Virginia Polytechnic Institute and State University * ************************************************************************* -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
