Years ago, Kirk Tuck wrote this piece on making portraits. It is definitely the best thing I have ever read on this process, and it's one of the best things I've read period. It's beautiful and true and packed with information.
I've seen a video of Karsh at work, and I read a detailed essay on Snowdon's approach. Both align with what Kirk has written here (Snowdon more than Karsh, one does not get a sense of collaboration but rather of combat with Karsh), but give only the external view. Kirk tells us what's going on inside. In all cases it is about seeking a moment. The technical details are minor, assumed to be dealt with, the subject and the moment is all. How you get there seems to vary, a little. In a striking contrast to the above portraitists, read this obituary for Jane Bown. And yet there are similarities.
This will sound goofy and woo-woo, but it feels almost as if the process arrives at a sort of Zen inversion where the camera simultaneously becomes nothing and everything.
I am, as the attentive readers likely know, fascinated by the process of portraiture. I have no chops with this device, but I've read a lot, and from time to time I take a pretty good photo of one of my kids. That's a very much more dynamic process, but ultimately the goal is the same. Every so often, mostly by accident, I find that moment when the kid has stopped mugging for the camera and is genuinely engaged elsewhere. Often with eating (the small one is two, after all).
Anyways, thanks ever so much to Kirk for digging this one out of the archives. There's also a list of links in a comment at this post, and they're all worth a read. One of them sounds very much like things I've said, but said better and a couple of years ahead of me. I don't think I plagiarized it, but one never really knows for sure what one has read, internalized, and forgotten.