Step 3: Blocking In
Once we've blocked in the basic colours of the background, skin and attire, it's time to focus more on values and lightning (Fig.04). Think in simple shapes when shading (the face could be broken down as a simple egg for example, the arms as cylinders, etc.) so we can establish a more believable lighting scheme. In this case, I decided to have a light source coming from the top left, and another one coming directly from the right. Be sure to shade all the elements accordingly to the light source to keep everything consistent. Avoid the urge to do any detail work, and concentrate on establishing basic forms. Don't undermine the use of values; colours can easily be altered in a program like Photoshop, values not so much. Concentrate on values first, colours later (although do choose a colour palette beforehand).
Start with fairly large brushes, and work your way towards smaller ones as you progress with the painting. This will help you to avoid detailing too early and will keep everything consistent.
Step 4: Shading
We shouldn't really be thinking about pushing the colours at this stage - we're looking to give the image a 3-Dimensional look, so push the shading quite a bit (Fig.05). A mid-tone, half-tone, strong highlight and a reflective light all help create a believe image, so keep all these elements in mind while shading. Work on all the elements uniformly, making sure that you spend equal time on each element for consistency. Bring out the form of pretty much everything you can; the clothing, bat, skin and so forth. As we continue to paint, slowly increase the DPI (ex. 72 DPI to 120 DPI) as we progress.
If you're feeling frustrated when shading something, always break it down. The human body, for example, can be thought as a bunch of cylinders, so shade them accordingly.
Step 5: Hard Edged Brushes
Most, if not all, of my shading is done by using a simple hard edged brush. So let's start off by having Pen Pressure set to "OFF"; however, after a while of painting, it's good to turn this feature on to help define the image more (especially as you up the res). Don't be too concerned about things looking ultra-smooth at this point, just make sure everything's strong defined (Fig.06). Using smaller brushes, bring out the form of everything you can and start to bring out the features more. Faces are always important, especially for an image like this, so be sure to spend a good amount of time working on the Joker's face.
Don't get ahead of yourself - that is, don't start adding details too early if you haven't already set up a decent base. The painting has to look good without all the unnecessary detailing for it to work, so be sure to take it one step at a time.