Lately, my lighting has become sophisticated enough to create those Joel Grimes 3 light tonemapped portraits. One advantage of this look, he discovered, is that it visually lends itself to compositing, with the subject isolated and then placed over a suitable background.
In the past when I’ve tried to isolate a hi-res portrait in GIMP (against a grey or white backdrop), it’s taken an immense effort. Joel is using Photoshop, so his techniques don’t really transfer. I’ve done my Google search, and I didn’t find anything different than what I tried, years ago.
I’m taking a little bit more time to up my “sophistication” in preparing an image for masking. There is a common technique that I only recently became aware that assists the process by taking two frames and serializes flash/strobe lighting. The first image is captured normally (with lighting) and the second frame only fires background lighting. The second frame is a silhouette of the subject, and both images are processed as two layers. Here’s an overview, and while many new strobes support alternating flash (e.g., Godox/Flashbpoint, Jinbei/Orlit, Hensel), it can obviously be done by hand.