Draw or paint your desk workspace as a still life.
Whatever you want.
Those with a full range of tonal value. Charcoal, paint, digital, etc. Graphite pencil if you have very soft, 7-9B pencils at your disposal. Pen and ink if you don't fear very subtle cross-hatching and/or dappling.
What Is the Point, Man?
: To emulate, as closely as possible, the phyiscal reality of the still life, as a test of one's pure observational and rendering skills. Without having to worry about subjects such as gesture, anatomy, style, etc., the focus becomes purely on being able to hone the essential skills of light, shade, form, and perspective.
Also, since most of us are lazy fucks, drawing your desk means you don't even have to get up or put any thought into getting a subject. It's right there in front of you, get at it.
How Long Should I Spend on This:
As long or as short as you want. This sort of rendering can admittedly take awhile, so it would be cool to see progress pics along the way, if you are really going all out.
Where's Your Picture, Asshole?:
What, that's it?:
Hey, I'm still working on it.
Only that if possible, it is probably preferable to have the lighting while you're drawing to be direct light- single lamps, rather than overhead fluorescent lighting. This way you can focus on looking how a single direct light source affects the lighting of the objects, rather than being befuddled by the comlexities resulting from a diffused, flat lighting setup. However, this is just a reccomendation.