Difference dcraw and dcraw_emu in sequential brightness.

Image icon dcrawvsdcrawemu.jpg236.18 KB

Case: i have two exactly the same images, shot with 5 seconds in between.
These two images are visually identical when viewed:
In their JPEG preview.
In Adobe ACR
In dcraw (tested v9.22, 9.24 and 9.25) with commands -T -w -W.

Then when i use dcraw_emu as:
dcraw_emu -T -w -W

The two sequential images have a slightly different exposure, one is brighter than the other. How can this be possible? A link to the two images I have hosted here: https://www.dropbox.com/s/qdmqgjie526ygmq/dcraw_emu_brightness_issue.zip... .

Please see if you can reproduce my result, or if you have any idea how this is possible. I have tried around 4 versions of LibRaw (and dcraw_emu) and they all produce the same erroneous result.


LibRaw (and dcraw_emu) with

LibRaw (and dcraw_emu) with default settings uses automatic maximum level detection (to prevent 'pink clouds effect', 5 years ago I've written small article about it, it is in Russian, but google translate will help: http://blog.lexa.ru/2010/03/28/taina_rozovykh_oblakov.html )

To turn this detector off (and produce results nearly the same as dcraw) use -e 0 switch of dcraw_emu.

-- Alex Tutubalin

Followup: maximum values in

Followup: maximum values in two files are differ: 12335 and 14213 in G1 channel. May be hotpixel, may be just signal variation

-- Alex Tutubalin

Hi Alex, Thanks. But:

Hi Alex, Thanks. But:
Tims-:bin tzaman$ ./dcraw_emu -T -w -W -e 0 /Volumes/TZ_USB3_32G/*.nef
Unknown option "-e".
Tim:bin tzaman$ ./dcraw_emu -T -w -W -e /Volumes/TZ_USB3_32G/*.nef
Unknown option "-e".

edit 1
Although i think you meant to say '-W'. This should turn auto brightening off, but it clearly does not for my images.

edit 2
Did you mean to say '-c 0' ?

Sure, I mean to say -c 0:

Sure, I mean to say -c 0:
-c float-num Set adjust maximum threshold (default 0.75)

Sorry for inconvenience, I need to sleep more :)

-- Alex Tutubalin

Worked great alex, you're the

Worked great alex, you're the man. No problem, you need to make a donation button somewhere, i'd get your some coffee ;).