Colors shifted when RGB composting

Hi there,

I am composting an RGB image from the three base R, G and B saved files. On the screen everything looks good, but then my colors are off when the fits file is saved.

I used drizzle so each R etc. file is 12448 x 8336, pretty big. I never had this problem w/o drizzle, smaller files ?

Tried adjust layer brightness but that did nothing.

Thanks guys, a bientot HWH

You need to apply a color calibration with the dedicated tool.

Thank you … in color calibration, manual or automatic white balance achieved nothing.

If you haven’t seen it already, you should look at this: Siril - Composition RVB

Since green channel is the darker channel, I’d start doing an offset of the other two channels towards the left to match the three channels. This is an easy action for instance substracting in Pixelmath the mean or the median of the green channel to the others; then rescale with the minimum and the maximum values of the channels. This is a linear transformation that will not produce any problem for future immage processing. Afterwords, do the steps by step of the tutorial indicated by @vinvin.

The background normalisation button, in the color calibration tool do the same. Automatically.

Ok thank you, automatic or manual color calibration works on 6224 x 4168 images, but not on drizzled 12448 x 8336 images.