So I've wanted to really improve my digital art for a long time, and thought that I should start now. So here I am.
I was captured by the light and mood of this scene with the contrasting light. The composition of this piece is based heavily on the rule of thirds with the horizon, wheelbarrow, and both figures lining up.
I limited myself to one hour, and although I haven't got a lot of the details in, I think the overall values are quite similar.
Nice work and interesting way to look for what to exercize. I feel some of the lights are a little off. Perhaps doing a gray scale would help you a lot. Do it with a 4b pencil, only. Let a gauge from 1 to 9, 1 being the darkest dark and 9, white. Start painting the halfway, 5, then 7, 3, and so on. Try and make a transition from one to nine with a smooth and almost suggested change. then after you nailed it - takes about 4, 5 tries -, try to guess which number you see in the values of the original you're working on.
Other than that, compositionwise, try not to think of leaving or making details, but to nail soft and hard edges. It will make it all come toguether with less effort and more efficiency.