I have been trying to use DT for the last days and I am missing one of my most common ways of working with Photoshop. I usually set black and white points in the curves module, identifying where to place the eyedroppers using the module’s clipping view (ALT/CMD key + moving sliders below the histogram). I have not seen a way to identify/choose the white points in a similar manner with DT.
This is a very fast and convenient way of eliminating casts and working on contrast at once.
Is there a way to identify black/white points in the DT RGB curves module like I have described above?
Welcome to the forum!
Darktable isn’t really oriented towards working with curves, although it can.
I’m not familiar with Ps, so hopefully others will have more direct suggestions, but if you’re working on raw images, by default the RGB curve module comes before the tone mapper (filmic or sigmoid usually) so it’s working on unbounded, linear or scene referred data. I think that would make it harder to do what you want - photoshop would be working on a display referred image that’s already been converted from raw I imagine?
I’ll have a look at the YT video you linked. Maybe I’m completely missing the point
Generally the focus in DT is scene-referred editing… so you define middle grey and then define how to map the tones above and below in fact initially this might show data quite severely clipped… this is fixed when you add a tonemapper… hard fixing black and white is more of a display referred way of editing… you can likely do it with levels or curves if you want but the advanced tools to handle this work with a different workflow in mind…
I had a look at the part of the video you linked - it seems that dt’s clipping indicator might do what you need? I’m not sure if you need it to respond to separate channels though.
Also, in rgb curves I think you’ll need to set “preserve colors” to “none” to get a classic tone curve response. See the short screen capture I’ve put below.
I’m not so sure about that now - the example in the video looks like it may have been converted from raw with a linear profile. You will want to switch off filmic or sigmoid though I suspect.
I should have linked to about a minute later on that video (now fixed in the first post). It is the clipping function in the curves module in PS used to identify the points + the way of doing a sort of white balance from those points what I am missing. This is on converted (not raw) images. I will try to get deeper into the way of doing things in DT (which is incredible by the way!), but I do miss such a powerful tool (for me ) in PS/Curves.
Sorry, I should have watched a bit longer… only excuse is I’ve had a busy morning.
Understand now. GIMP’s curves tool does have the white and black point eyedroppers… but I’m not well up with GIMP and don’t know if there’s a clipping indicator.
Hmmm…
Darktable does have a different approach in some things… it can be a culture shock!
This from the manual sort of introduces you to the concept… so not thinking about setting fixed black and white points… It becomes more about setting exposure to anchor middle gray and then tone mapping from there…
As such I don’t think you will be able to use the tone curve module in DT as it is shown and used in your video… You can manually adjust individual rgb curves but there are not similar picker functions in the curves module
Hi Madera, welcome to the forum. You will find the people here are very helpful and willing to help.
So DT has curves. I suspect they act similar to PS, but I abandoned PS many decades ago despite having a perpetual licence for CS6 so I am no expert on PS. PS doesn’t process RAW files so I wonder if you are processing RAW files or JPGs (or something else)?
However, DT’s RGB curves probably show what you want if you tick the compensate middle grey box. I must confess that the curve makes more sense to me when this box is ticked so I am unsure why the default is unticked.
But the difference appears to be that photoshop had black and white and grey droppers that set those points … so you could be in the view that DT uses for linked and slide that curve to the black and white points… all the same up to this point but then if you select the pickers it seems to be the same as if you went in and did this independently for each unlinked curve. THe grey is also operating independently on the 3 curves so you get almost an auto wb… you can see it in the video link that was shared. So I think you can do it in DT but you would need to do it all manually… If the pickers are actually doing tonal WB that would be slightly different I think and more like this tool in PWP8 or maybe tweaking things with the pickers in rgb CB
Put the RGB curve above filmic or sigmoid (or don’t use filmic or sigmoid at all, unconventional use of DT) and enable the clipping alerts to adjust luminosity and/or the white and black point.
Leave the module as is and alter colors by editing the RGB curves, perhaps changing the blending mode to chromaticity.
Also to mimic PS you should change the curve type to 'cubic spline".
you can select points or areas with the global color picker on the left panel and add them to live samples. If you then activate the color picker in the rgb curve module you’ll see green lines representing the live values and a red line representing the live values.
Then you can set your controlpoints via ctrl+click
But this workflow indicates: that’s not the darktable way to eliminate color casts…
Hi Madera, I would recommend learning the modules designed to adjust color casts in DT which starts with the color calibration module. I too first learnt photo editing with Photoshop (and then switched to GIMP) and I was used to using curves to adjust colors. Even now I will after color calibration has done the heavy lifting I will do a final tweak with RGB curves in DT. The attached image shows how I would reduce a blue cast by lowering the blue curve in the centre. Alternatively, I could removed a yellow cast by raising the blue curve. The red and green curves work the same way for the respectively with the complementary colors. But the RGB curves are not designed to be the main color correction means in DT. Good luck with your editing.
