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Deladier,

The only observation I might make to this very beautiful piece is along the lines of color temperature. Both the lit and shadowed sides of the face are hot. Given the light source you are dealing with, you might think about cooling the shadowed side of the face (and all other shadows, of course) with greens, violets or blues.

If this was my painting, I'd probably cool with green-blues, in the same value as you now have in place.

Nice work.

To me the lit side of the face looks "cool" and the shadowed side looks "warm". They are both red/pink, but the lit side is cool pink and the shadows are warm red.
I always thought that red, like green, can be either warm or cool.

The shadow knows
 

I think the problem is the discrepancy between the different shadow areas. Whatever is influencing the shadow side of the face obviously is having no bearing on the shadows of the shirt. All shadows need to be consistent, color influence and temperature wise, or the painting looses unity. The same holds true for the lights.

You both gained and lost ground on the eyes. Consider:

1) In the photo, I don't see any of the whites of the eyes -- in either eye -- on our left side of the eyes. Yet I see a crescent of white alongside the iris in both the eyes in the painting, and it's pulling toward us a part of the eye that should be receding and saying "round".

2) The whites of the eyes that we can and should see, on our right, are too white. (Yeah, in the photo, too. Forget the photo.) Gray them down a bit, again to help round out the form. The bright, colorful irises should be closest to us.

3) The pupils are so small as to suggest the influence of some bright light behind the photographer. If this subject's pupils are in fact naturally small, all the time, then fine, that's a characterizing quality. But the tiny pupils are part of what's making the two eyes focus on markedly different points. Enlarge them just a bit and the effect is substantial. (They won't be quite so laser-beamed at small targets.)

4) The iris of the eye on our right has become oblong, rather than round.

Consider wiping out that eye on our right completely, and putting it in again. (I was once told to do that, and I protested that I'd never get the eye "right" again. The instructor was incredulous (it was the first time I'd seen him do a double-take, as if he couldn't believe what he'd just heard). "You'll have to," he said. And that was that. And I did.

And again, Squint! at the photo (as you would at the subject if this were from life). If you can't see a value when you squint, it likely doesn't even need to be in your painting. Otherwise, you're going to be overmodeling, or looking for lights within shadow areas.

The toughest thing...
 

It is one of the toughest things, to get the right shadow colors from photos. Painting from life, it is remarkably easy in comparison. Shadows must NOT be intense re: chroma. As mentioned by others you have hints to go by in the photo. The white shirt will help you to read the color of light and then you can extrapolate to find the temperatures of the shadows (to some degree).

The problem is that cameras don't read shadows very well. If you were working from life you could squint at the ACTUAL subject and compare your subject to your painting and the answer would come to you quite naturally. Can you get him to sit again? Adjust this from life if you can.

Deladier, I love watching your portraits build, and am not sure if anyone has asked you, but I finally put my finger on it, have you ever studied with John Howard Sanden? They remind me of his.

Beautiful work.

Done
 

Here is the final on this study.

My goal in this piece was to get a run through all the passages I will be rendering in the final painting, as well as experimenting with the light without commitment to exactness.

My intention was actually to have stopped sooner than this but your comments encouraged me to refine it further and that was great. It was an excellent exercise and I now feel much more confident and ready to proceed with the real thing.

Thank you all who took time to offer me those critical comments and suggestions.

Bravo for making time a consideration! Time is the dictator of style, and if you set no limits on it, you run the risk of wasting it. Great stylish work, even if the proportions are a bit weak.