This question is in two parts. Context: my camera has the ability, while working in JPG mode, to take a B&W photograph except for one colour. I can select red, blue, green, yellow. Check your own DSLR, you may have something similar.
Imagine taking a oblique view of a parking lot, the cars all parked nose-in and the sunlight reflecting off their red rear reflectors. Capture that; the cars in B&W (unless there is one that's a bright red sports!) but just the red reflectors lit up. Sidebar: I've just tried this with some pictures of evergreen in the snow, but I don't think much of the result. My first question is this: I have older photographs in full colour taken with other cameras, some with film that has been scanned. Can I get Darktable to do this transform? The answer must be 'yes', but I get confused along the way. I see in the docco that there are a quote a number of different RGB settings that can make up B&W for various different types of B&W film. I can imagine picking one or another or another and then sliding the RED up in colour adjustment. But that doesn't give me what I want. How do I get yellow? What if I take a picture of one of downtown buildings that has gold plated thermally efficient windows and just want the gold to stand out? I can imagine more grief with masking! The second question is a good but more complicated and I realise it probably does involve masking. There are a number of structures that are like maypoles, they are colourful, multicoloured. So I can't simply go B&W and then pull back colours. I can see this being done in GIMP with a couple of layers; pull out the maypole, make the rest of the image B&W in anther lay, overlay. But is there a straight forward way t do this in Darktable without combining overlays, a sort of HDR for a single feature? All of this without getting too complex, perhaps make it script-able. ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to [email protected]
