If one follows the DNG spec for raw conversion there are several checkpoints during the process where one needs to block negative values to zero. At each of such points I add the relative pixels to an out-of-gamut RGB image. Values are set to either 255 or zero in the appropriate color plane. I usually carry clipped pixels over then just after projection to the destination color space, but before any further processing, I add in those as well. It’s usually obvious by comparison to the rendered image which are clipped vs blocked.
The resulting image above doesn’t show you by how much values are blocked/clipped, just that they are. I find it is useful to quickly see how much clipping/blocking is due to somewhat objective ‘gamut’ issues vs subjective ones by further processing, as in this discussion. Not many options for the operator with the former, many more for the latter.
Assuming the DNG spec process, the checkpoints I use are basically in linear space just after matrix multiplication:
- conversion to XYZ
- conversion to ProPhoto (if LUTs are in the dcp)
- conversion to destination color space.
These are the stats I get using the DNG tags for the capture in this thread with ‘basic’ table:
Ant these are for the same with the ‘look’ table applied:
I don’t know what part of this functionality is available in raw converters discussed around here.
Jack