Use multiple channels to make your selection. I often find that using the L channel and the Hue channel together work well. But you have to look at your photo and ask yourself how the area you want to make differs from the area around it. Just by looking at this photo, if you wanted to select the horse, the L channel and C channel might work well.
Use the eye dropper tool to look at where colors fall in the mask sliders
Almost always use drawn + parametric. I start with parametric and narrow my selection as much as possible, then refine that selection with a drawn mask.
OK…how do I choose multiple channels? One after the other or is there a way of selecting two at the same time?
I know that sounds very stupid, but…
So…I use the dropper…a little bar appears on the slider…where next? Assuming I want to isolate and modify the horse, do I close up the top sliders around the mark and leave the bottom slider where it is? Or vice versa?
These are good as well…https://www.youtube.com/watch?v=RkNU8qw9Aco for working with mask combinations and this one https://www.youtube.com/watch?v=sKYI_oT1XFs will show you have to achieve what you are looking for…one tip would be often it is easier to create a mask of what you don’t want then invert it to give you your mask…here you have a lot of green in the background so you might be able to mask that and then invert it to leave you with the horse…
Along with the links mentioned above, Bruce Williams (https://www.youtube.com/user/audio2u/videos) has a 5 part series explaining masks - Episodes 13 through 16, which give examples of the various masks. I believe he discusses the input and output sliders in one of those videos, as well as in a more recent video - Episode 39 Masks Part 5 Output sliders.
If you are new to darktable, his entire series of videos (46 videos to date) may provide you with a good foundation from which to proceed.
Any general hints?
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