Painting with Gradient Maps

One of the disadvantages to painting in Adobe Photoshop is the fact that the brushes act rather like stamps; a single color is deposited on the digital canvas wherever the brush travels. The Color Dynamics options allow a second color to be introduced, but their functionality is limited. Sometimes, it is desirable to create complex blends of color using a simple workflow, especially when painting clouds or the like. In such cases, Photoshop's Gradient Map feature becomes very useful.

1 What is a Gradient Map?
2 Using Gradient Maps in a Painting
3 Tips
4 Links

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What is a Gradient Map?

A Gradient Map is an adjustment that can be made to a layer or selection. (This can be found under Image > Adjustments > Gradient Map.) Photoshop looks at the grayscale value of every pixel and assigns it a new color based on that value. The new colors are represented by a single gradient in the dialog box. Imagine a white circle and a gray rectangle on a black background. A Gradient Map is then applied to this, with the gradient running from blue on the left to red on the right. The resulting image will show a red circle and a purple rectangle on a blue background.

In order to keep images easily editable, it's advisable to use Gradient Maps via Adjustment Layers. Layer > New Adjustment Layer > Gradient Map allows a Gradient Map to be applied as its own layer. At any point, the gradient or the underlying image can be freely edited.

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Using Gradient Maps in a Painting

Create a new layer for painting on and fill it with black. Go Layer > New Adjustment Layer > Gradient Map and fill in the dialog box as desired. Now click the gradient bar that appears; a standard gradient editor should open. New colors can be added to the gradient by clicking just below the gradient; color boxes can be edited by clicking them. Be sure to drag the color boxes to appropriate positions. Try to develop a palette that runs from dark on the left to bright on the right, encompassing all the desired colors for this part of the painting. Once the gradient is satisfactory, hit OK.

A new layer with a gradient-like thumbnail should appear on the Layers palette, just above the painting layer. Alt-click the border in the palette between the two layers; the cursor should change while alt being held and the adjustment layer should indent to the right. (This causes the adjustment layer to only affect the one painting layer.)

At this point, the only thing left to do is paint on the black painting layer. The adjustment layer will continuously apply the Gradient Map to the layer, so the colors in the gradient will appear on the digital canvas, no matter what colors are used in the painting process. If the gradient needs to be tweaked, feel free to make changes by double-clicking the gradient thumbnail on the Layers palette. Alternatively, you can create a white fill layer with a mask above the black layer and paint within the mask instead.

When working this way, brushes can be tweaked to streamline the workflow. Rather than using pen pressure for Opacity and Flow, use pen pressure for foreground/background jitter (under Color Dynamics on the Brushes palette). Be sure to set the foreground and background colors as black and white (or vice versa, depending on which is more convenient). Pressing hard produces color from one end of the gradient, pressing lightly produces color from the other end, and using medium pressure allows the middle colors in the gradient to be revealed. For best results, set the Flow value low.

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Tips

Try to paint only in white, black, and grays; let the Gradient Map create the colors. Using colors in the painting process itself is pointless and can lead to confusion.
Remember that alt-clicking parts of the painting to sample colors isn't effective when a Gradient Map is activated.
Rarely will the results of this type of painting be complete or perfect. In most cases, it's wise to create one or more new layers above the adjustment layer and paint changes there. This allows new colors to be introduced to specific areas.
The same sort of process can be carried out using Color Balance rather than Gradient Map, though the results are somewhat harder to control.

A couple of the above issues can be avoided if instead of directly painting on the layer, you create a white fill layer with a mask directly above the black layer. By painting within the mask, you no longer have to worry about painting in grays or being unable to alt-click to select a "color" created by the gradient map.

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Painting with Gradient Maps

Contents

What is a Gradient Map?

Using Gradient Maps in a Painting

Tips

Links