RawTherapee Dark-Frame auto-selection picks only 1 file

wincent · December 17, 2020, 1:49am

Hello all,
First message here, I hope I follow the rules for posting.

I use RawTherapee for demosaicing astrophotos.
I have 5 dark-frames that I took right-after the star images : same ISO, same camera, same exposure duration and almost same time (less than a minute difference).
If I select one of them as a Dark-Frame, I can see at zoom level = 100% that it actually worsens the “noise”.
So I hoped that by using the Auto-selection tick box, RawTherapee would average my 5 dark-frames and subtract this average dark-frame to my star picture.
However, it seems to me that only 1 dark-frame is selected (see attached screenshot).

How can I force RawTherapee to average my 5 dark-frames ?

I know that I could create an average dark-frame (or “master dark”) with astro-programs like Siril, but they produce a .tiff file that cannot be subtracted to my raw photo in Rawtherapee. I have already tried, but no effect at all is visible. Perhaps RawTherapee detects the dimension, color space and/or CFA are different and as a result abort the dark-frame subtraction.

Waveluke · December 23, 2020, 10:12pm

Use imagemagick to convert from the SIRIL produced tiff to dng, using the command

magick stacked_dark.tiff stacked_dark.dng

Then use exiftool to copy the tags from an original file with the same exposure settings to the new dng to finish the process

exiftool -tagsFromFile direct_from_camera_raw.RAF -x BitsPerSample stacked_dark.dng

Then in the file browser for selecting dark frames, go to the bottom right corner and switch from “same as current photo(RAF)” to “All files”, and your fake raw dng should appear in the directory.

flint · February 5, 2021, 5:21pm

Hi wincent,

Did you ever find a solution to this problem? I have the same issue; that is, I put multiple dark frames from same camera, iso, shutter speed etc in the darks folder specified in preferences. RawTherapee seems to group them correctly and creates 1 template.

But as you reported, only 1 file from the group is selected when the Auto-selection box is checked.

ChasingShadows · February 5, 2021, 9:05pm

As far as I know only one file, the best matching one, is selected. If multiple files with same settings exist, only the newest one is considered. As I said, as far as I know …

heckflosse · February 5, 2021, 10:31pm

Sounds like a bug, as there is code to average dark frames

github.com

Beep6581/RawTherapee/blob/dev/rtengine/dfmanager.cc#L137


        updateRawImage();
        updateBadPixelList( ri );
    }
    return badPixels;
}
/* updateRawImage() load into ri the actual pixel data from pathname if there is a single shot
 * otherwise load each file from the pathNames list and extract a template from the media;
 * the first file is used also for reading all information other than pixels
 */
void dfInfo::updateRawImage()
{
    typedef unsigned int acc_t;
    if( !pathNames.empty() ) {
        std::list<Glib::ustring>::iterator iName = pathNames.begin();
        ri = new RawImage(*iName); // First file used also for extra pixels information (width,height, shutter, filters etc.. )
        if( ri->loadRaw(true)) {
            delete ri;
            ri = nullptr;