Latest update to this plug-in.
I discovered an error in the creation of the Contrast layer. (I always make mistakes in Python programs and discover them later!) This has now been corrected and i have replaced the file (above).
The Stretch Contrast option (the default) improves the colour correction, not only for those images initially lacking in contrast, but also those where the histogram spreads across the whole of the range.
After running the plug-in, the contrast can be changed by altering the opacity of the Contrast layer (default 10%) and the amount of colour correction can be adjusted by the use of Colours/Saturation on the Colour layer.
I have been able to carry out a limited amount of testing by “borrowing” a number of examples found in a paper on the internet. However, these are not in the public domain so I cannot show them here.
If anyone can provide me with examples it will enable me to test further.
Many thanks for these examples. They will allow me to carry out more testing to see if there is anything I need to change or improve.
I have downloaded them. A quick observation suggests that they have produced an improvement in every one. Some of them are extreme examples which make them particularly useful as I will be easily able to see the changes in the histogram.
For anyone who has downloaded my colour correction plug-in, there is a new version.
The operation of it has not changed, but I found that it took a very long time when used on large images. It has been amended to overcome the problem.
In the entry No. 41 (above) by Zbyma72age, CCR1 references results from my GIMP Python plug-in (col-cast-reduction1.py).
Having tried all these on my machine I get identical results using the plug-in with it’s default values. After running the plug-in further adjustments to the result are available by:
Changing the opacity of the Contrast layer (contrast adjustment)
Changing the Colour layer using Colours/Saturation (degree of colour correction)
Using any of the options in the Colour menu to make changes to the original (base) layer.
I hope this is of help.
The zipped plug-in can be found at entry No. 43 of this thread.
With each new version of darktable, I find myself re-evaluating/re-working my older images.
I am currently fully reworking a series of 1985 film material that was professionally scanned into (low res.) tiff files.
My original processing was in 2018 and compared with today’s version of darktable I see substantial improvements using just the basic modules.
