Creating the illusion of three dimensional form on a flat surface is the main priority of the representational artist. Within the realm of representational art making, there is a broad range of solutions for recreating our observed world.
On one end of that range, you have artists such as Monet and his Impressionist contemporaries, for whom colour and atmosphere are paramount. The works of the Impressionists are certainly evocative of how one might see, or even feel, upon gazing out at the world, but their work doesn’t necessarily convey a great sense of volume through contrast. Try taking a reproduction of an Impressionist painting and desaturate it, making it black and white. There’s actually very little contrast within the works. Without colour many Impressionist paintings actually look quite flat and devoid of three dimensional qualities. Nothing wrong with that though. As representational pictures, they occupy the flatter, more decorative side of the gamut of what looks “real” to our eyes.
On the other end of the spectrum, one finds works by such artists as Caravaggio, Velazquez, Bouguereau, among many others. The works by these artists function much more convincingly as illusions of reality due to their much greater use of a range of contrast between light and darks of the picture.
One complaint that comes up time and time again here in the studio when people are starting their journey to become capable representational artists, is that they feel like their pictures look unconvincing and flat. Almost always, the solution to this dilemma is to increase the amount of contrast that is utilised in the work. So what does that mean if one is using a white piece of paper for instance to draw on? There’s only one way to get greater contrast, and that is to get darker.
Try it out with your own work if you feel that it looks less realistic than you’d like it to appear. Really push your darks as dark as you can get them. By using darker tones, the light areas of your picture will look lighter in comparison. Remember, you can’t have light in your pictures without darks.