Composition: Excellent composition. Wonderful use of space. Depth of field is perfect, clearly showing the artist and his instrument. The capture of the expression of the musician is wonderful and complemented nicely by the warm lighting. I really get a feeling of warmth and peacefulness from this image. The only thing I would like is a touch of unsharp mask - I suspect that when you resized this it got a little soft, and I would love to see tiny details in the man's face, like eyelashes, etc. I think that would really make it "pop" off the screen.
Challenge: You've met the challenge criteria extremely well. The feeling of silence that this conveys is wonderful.
My Opinion: Overall, I really like this. It's hard to capture mood so well in a photo, especially with people. I'm a bit curious to know if he was modeling for you or if you somehow grabbed this shot candidly. Either way, it's a beautiful portrait of a musician.
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Interesting image, lighting doesn't work for me - I just don't like that red-orange colour of skin. It may not have been possible to throw more light on the subject, perhaps a higher ISO rating might have helped?