Turning form so that it appears natural is perhaps one of the hardest things to do with color. Creating a value range by tinting a single color may result in an accurate light to dark rendering, but it will look like a colorized photograph, and not natural.
A rounded object, like a ball, will have a local color that changes in hue based on the temperature of the light. If the source light is warm, the shadow areas will tend to appear cooler. Even though the objective local color of the ball may not change, the perceived color does change due to hue shift on tint. As the form turns, the light hitting it changes in color also, further impacting the hue shift in perceived color. Thus it will not suffice to have a blend of one single hue to several light and dark greys because most certainly the light colors will need a color hue that is different from the shadow areas. Thus we need progressions from light to dark that also shift hue along the way. To master form, you have to mix color progressions that are true to the perceived hue shifts.
Let’s use the apple on my desk as an example. I photographed it an used a graphics program to inspect the pixel colors.
The first column (A) shows the hue-saturation-brightness (HSB) color values as detected on the photograph. Note the variety in hues, from #44 through #51, all of which describe a ‘yellow-green’ apple. That’s a lot of colors to mix, and a typical beginner approach is to replicate each one individually.
The second (B) shows a ‘colorized’ simplistic approach to mixing the apple colors, i.e. simply taking the lightest and darkest and blending them in steps. While this is expedient and the diligent artist can of course produce a realistic looking apple if the values are carefully observed. Remember, if the values are correct, the image will be impressive even if the color variety isn’t as rich as in nature.
The third column (C) represents a more differentiated approach that both avoids having to mix every variation perceived, yet at the same time provides accurate tonal value range for a realistic rendering without sacrificing naturalistic color variety. The artist identifies a few key colors in the progression that represent HSB ‘way points’:
21 – The brightest color next to the highlight. Remember that the highlight itself is an almost a pure reflection of the light source and won’t have any local color. So it’s best to start next to the highlight.
24 – A close approximation of the local color before the form turns into the shadow area. The other colors, 22 and 23, can be blended on the fly by mixing 21 and 24.
27 – The color of the core shadow. This is where the form turn away from the viewer toward the shadow areas and is typically the darkest area on the main surfaces of the object itself. (The pit of the shadow area will often be darker.)
30 – Color of the reflected light. In this case, it is the warmer light is reflecting onto the right side of the apple. There is also a cool reflected light on the opposite side.
The final progression is for the shadow areas. There was another cooler daylight light source that hit the shadow areas. Two boundary colors were established for this progression, 31 and 34. The intermediate colors 32 and 33 can be mixed on the fly as needed.
Thus to render this apple, the artist would pre-mix four colors in the primary progression, and two in the secondary shadow area. Some economy of mixing can be achieved by using the local color (24) and diminishing the saturation and brightness a bit to get the warm reflected light color (30). In other words, mix five colors (three for the warmer progression and two for the shadow area, and then mix the warm reflected light color as a variant of the midtone color).
Warm-cool color oscillation can add interest in the shadow areas. This can be achieved simply by putting some cool reflected light color (34) in the area of the warm (30), and visa versa. Care has to be taken not to overdo it and thereby loose the differentiation between cool and warm areas of the shadows. A similar approach can be taken on the lighter areas by creating cooler variants at the end and strategically mixing them in. All the variations, however, should not interfere with the systematic approach that will allow you to put down the illusion of unified form that has naturalistic color. Anomalies can then be added opportunistically for interest. This is how masters astonish us with both speed of execution and naturalism of form. This approach is the opposite of the tendency artists have as keen observers to major on the variations, which only results in a noisy and fragmented visual experience.
copyright © 2014 roy zuniga