Great job on the sketches. I personally find the proportions in your sketch pretty good, not 100% photo-like accurate but I don’t think it has to be. Only comment I have is that your contour lines seems a bit too evenly weighted, and most shadows as well, which makes the image just a bit flatter than the examples. Some places where there are no deep crevices or great planes changes the contours are more subtle, so you should use the contrast between the shadows values of the form more than drawing contours there. That said I’m not an expert at this either, this is just my 2 cents.
I’m also wondering, where do you get the figure photo references for your sketches?
