Drawing a great portrait or tackling a figure drawing is something we all want to do. What can be more expressive than the human figure and face? Whether it's a portrait of a wise old man or a drawing of a broken angel, the innocent joy in a child's eyes or the black tears of gothic pain, we love the most challenging subjects. But for the developing artist, it's a bit like a musician trying to only play a great concerto and skipping the scales. I know you don't want to believe me, but going straight for the masterpiece really isn't a good idea.
So what is wrong with this approach?First, there are a lot of stages to go through in creating a complete drawing. Mistakes at each stage tend to compound each other. An error in judging proportion can lead to awkward distortions. For example, you think the problem might be with the shape of your ear, when the real problem is the size of the jaw you're drawing it on. Cramped placement of features can lead to exaggerated shading as you try to make it 'look right' but without fixing the underlying problem. Then there's issues of shading and modeling the features, and the choice and range of values. Finally attention to detail, and again, representing detail becomes a problem if there are any distortions. Even when the details are handled accurately, slight problems in structure can make the face look distorted or even oddly boneless.
Because there are so many complicated elements involved, it can be quite difficult to troubleshoot a major work like this. Not only is there the problem of compounding errors discussed above, but also with many small flaws, it can seem like nothing is right - you just get a general sense of 'something wrong' and can feel very frustrated, not knowing how to fix your work. It's difficult for a teacher too, because there can be many small issues, so they sound overly critical, instead of being able to focus on one definite problem at a time.
This doesn't mean you shouldn't do big, adventurous subjects, portraits and figures when you're learning - especially if they are an important part of your self-expression. On the contrary, it's important do do the work you love to do. But if you only work in this way, you are likely to become frustrated with lack of progress.
A Better Way to LearnIf you want to develop your skills and have complete artistic freedom, you really do need to do some focused drawing exercises. Try to set aside a regular time to do some drawing exercises, either before you get to work on your expressive art, or perhaps one afternoon each week. You can do the drawing exercises on scrap paper if you want, or have a sketch pad set aside for them, if you don't want your favorite sketchbook to be filled with such mundane subjects. For line work, any paper will do, though a better quality paper will give better results for value studies.
Remember that the point of a drawing exercise is to develop specific skills. This should be clear from the instructions - whether it is about gesture, foreshortening, perspective, proportion, light and shade, tonal range or so on. While you might decide that you want to add some detail and shading to your perspective drawing, you don't have to. Similarly, with a value exercise, obsessing about perfect perspective might just be a distraction.