Question about "maximum", "channel_maximum[4]" data fields and an observaition...


I noticed that when exp_shift is used, the "maximum", "channel_maximum[4]" data fields are corrected accordingly by the exp_shift value. Why is that needed. I mean if a 12bit raw value is for example 3000, what is the reason to double it (exp_shift == 2.0) when 6000 exceeds the 12bit max possible value 4095?
Also I noticed in the latest release that when an image is opened in half_mode and then reopened to full resolution the four_color_rgb switch seem to be on and cannot be off even if explicitly set to 0. This was first observed in the past (release 0.11 i think) but then it was fixed.
Thank you for the answers and thank you very much for providing LibRaw!



You're right, positive

You're right, positive exposure shift without highlights compression will not affect entire image with default processing options, because data will be scaled to full 0..65535 range on postprocessing.

Anyway, positive exposure correcton is useful if
1) Manual data scaling is selected
2) Or highlights compression is non-zero.

Thank you for four_color/half_size report, I'll check.

Sorry for delayed answer, just returned from long vacation trip to Mongolia without any internet access....

-- Alex Tutubalin @LibRaw LLC

four_color_rgb value is saved

four_color_rgb value is saved in the beginning of dcraw_process() call, may be changed by half_size setting, but restored again at the end of dcraw_process(), just before return. (LibRaw 0.13.5)

Could you please provide sample code with errorneous four_color_rgb/half_size behaviour?

-- Alex Tutubalin @LibRaw LLC

Thank you for your reply.

Thank you for your reply. Writing a simple program cannot reproduce the problem (four_color/half_size). So the error is somewhere in my own code. For the moment I cannot find it but I will.
Thanks again.