The images I have been trying with are 8288 x 5520 16-bit FP. The problem only arises when Select-by-Colour is of a substantial part of the image. I waited 15 minutes for it to Save-Selection-to-Channel without success. This is with a 4GB/sec processor of 8 cores and 32 GB of RAM.
I have confirmed this with other images derived from RAWs of various sorts, all converted to 16-bit FP.
It would appear that for large images I may have to find alternative ways of making selections so that I can make adjustments to various regions.
Thanks for all your help and apologies if I have sent you on a wild goose chase.
Edit: @ Rich. I don't have any appimage versions of GIMP. I checked that libtiff5 is up-to-date. File conversions were done with Filmulator and NuFraw.
I have confirmed this with other images derived from RAWs of various sorts, all converted to 16-bit FP.
It would appear that for large images I may have to find alternative ways of making selections so that I can make adjustments to various regions.
Thanks for all your help and apologies if I have sent you on a wild goose chase.
Edit: @ Rich. I don't have any appimage versions of GIMP. I checked that libtiff5 is up-to-date. File conversions were done with Filmulator and NuFraw.