What are the difficulties in separating cast shadow from reflected light and shade?
The cast shadow should be much darker than the reflected shade, I realise looking back at my images that I have frequently not made this distinction. The milk jug is probably the example where this has worked best.
The first difficulty is identifying where the cast shadow is and where the areas of reflected light and shade are. The next problem is to actually distinguish between them in the drawing. I need to be able to produce a wide range of tonal values in order to distinguish the variation between these.
The other problem I had was working with charcoal - I like this medium but do find it problematic maintaining areas of white highlight. It is important to remember to look for that fine rim of reflected light at the edge of an object before putting the cast shadow in because it is difficult to lift it back out once a thick area of shading has been applied.
The reflected shadow and light follows the contours of the objects. How have you shown this in your drawings?
I've done this without really thinking about it. The drawing tool such as the side of the charcoal stick automatically follows the contour of the object when shading.