Wibble, I feel you need to check your measurements his face is wider than the drawing, that’s the first place I would go.

eyes too big. Face a little long. Hope it helps

Thanks again to everyone who provided their feedback. Here's another portrait in which I tried to action your comments.

Your use of value is very good. When you look at each feature in its own you can see how well you are drawing what you see. You have a natural talent for being able to catch the nuances that bring the characteristics into view. I am certain that once you practice the proportions of the face you will see improvement by leaps and bounds. I’m looking forward to seeing your progression. Don’t give up! Have you considered trying to draw this upside down to use you strengths and it will trick your brain out of outing facial featUrea where you think they should be versus where they are. Keep going.

I suggest you use a couple of strait lines to make the eyelids around the eyes. I struggle with it myself, but i've noticed that making the lids with straight lines I can show the lids wrapping around the eyeballs.

I think a good opportunity for you would be to try to unify all of the individual parts. Each part is fine on its own, but as a gestalt it appears abit uncanny and out-of-perspective. Perhaps you can do some 3d sketches of cubes, and study how the mid-points and thirds of cubes look in space. Bridgeman's cuboid faces are amazing for learning how to space things properly. Kudos on your shading and use of value! It is very strong!

I think it's great that you created a value scale for reference, and something else that can help judge values correctly is also using a blurred version of the reference (or squinting at it). That way, you are thinking more about the larger groups of value, without as much distraction from details or preconceived ideas of what things are supposed to look like. For example, a common mistake is making the whites of the eyes lighter than they really are because we think of them as white in value, when often times they are darker due to shadows. Working like this in larger groups of value will help you tackle more complex drawings like portraits, help you assess your drawing directly against the reference, and make it easier to spot mistakes. Comparing the two right now using this method, I would say the jaw area under his cheekbones, his upper lip, eyes, and the hair shine are areas that could benefit from both simplification and being darkened a bit. Hope this helps!

Nice job on this, the proportions look pretty good and you seemed to have captured the likeness. There are some alignment issues like the mouth and nose. I did a quick diagram to show you what I mean. Also, try to find reference that has a single light source, it's much easier to judge your values and make it look more dimensional.