Simply put, a painting is a bunch of different colored shapes. The configuration on these colors have been discussed here and the placement of the shapes have been discussed here. The only significant thing left to discus is the edges of those shapes.
For a major part part of Western art history and most of non Western art history, shapes within paintings have been hard edged. There are various reasons why this is so, but mostly it is because of the limitations of the painting medium that was used in their making. Very quick drying paints, such as those used in fresco painting, make it difficult to blend edges. Soft edges made their first appearance with the invention of oil paint. Oil paint stays ‘workable’ for a long time and therefore the edges can be blended easily.
To be able to soften the edges within a painting is a significant ability. Soft edges mean that paintings could be imbued with more realism. You may break down your edges in much the same three-fold manner that you break down your tones: hard edge, medium edge and soft edge. Furthermore, the perimeter of a region (AKA a shape) may exhibit significant variance in edge qualities: e.g. soft one side, hard the other.
Look at the detail of a painting by Renoir below, see how the edge of the girl’s face is so soft it can barely be distinguished from its background. The edge of the ear is harder but not as hard as the edge of the collar.
Below is a breakdown of how large edges may be used in the creation of a space, in this case a vista.
Lines and shadows
Lines are particularly important in the painting of shadows. The most important thing to know is the difference between a cast shadow (e.g. the shadow you cast upon the ground) and form shadow (e.g. the way that the side of a ball that is facing away from the light is darker than that which is facing towards it). Cast shadows often have hard edges, whilst form shadows often have very diffuse edges. The image set below shows the cast and form shadows upon a face:
In the image below, the following points are illustrated:
- A cast shadow, which is on a different plane to it’s source, blurs the further it gets away from that source.
- A shadow that is on a plane that is parallel to it’s source will have even edges, all of the same blur value.
- A shadow undergoes a sudden increase in intensity where it meets it’s source (especially ‘underneath the feet’ of that source). This is sometimes referred to as the ‘root’ of the shadow.
- A shadow IS NOT A THING. It is merely a less well lit portion of the thing on which it lives. Remember this when you are determining the color of a shadow (see how the difference between the red line and the white floor is consistent both in and out of the shadow).
- A shadow can describe the form of the thing it is cast upon. It can also describe the position of the object that is casting it. See how the shadow of the small pipe is dropping down onto the large structure.
- Form shadow (point 6) should be considered separately from cast shadow. See how the shadow cast by the floating cylinder onto the standing cylinder at point 5 is slightly more hard edged than the form shadow of the standing cylinder.