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November
2001

Transparency and Blending Modes

The last two months, I have addressed using layers and masks in Adobe Photoshop to create sophisticated composite images. This month we move to a related topic, transparency and compositing or blending modes. These tools are also available in Photoshop Elements and other image editing programs.

Fig. 1

Photoshop’s Layers palette is the control center for all of these tools (Fig 1). At the top is an Opacity slider and pop-up menu of Blending Modes. The Opacity slider is very straightforward. At 100% opacity, that layer is totally visible and covers up any image beneath it. At 0%, the layer is totally transparent, the layer beneath shows through. Any number in between can be used for varying levels of opacity. Multiple layers can be composited diaphanously for an artistic effect.

Layer Masks allow for more control of transparency. Unfortunately for users of Photoshop Elements, this is one of the features that Adobe did not include so you can skip to the next paragraph. In a Layer Mask, white makes the layer opaque and black makes it transparent. Shades of gray give levels of translucence. All of the usual painting tools can be used on a Layer Mask including Brushes and Gradients. Figure 2 shows an image with a gradation on a Layer Mask.

Fig. 2

Blending Modes allow layers to behave differently than simply being transparent or translucent. The default blending mode is ‘Normal,’ but there are several others (Fig 3). Experimentation is the best way to learn how these different modes will affect your specific images, but here are some general principles.

Fig. 3

The most useful blending modes are ‘Multiply’ and ‘Screen.’ These are basically opposites of each other. Multiply mode makes everything in the layer that is white to be completely transparent and everything that is black to be completely opaque. Shades of gray will have an equivalent degree of opacity. Screen mode makes white areas opaque and black areas clear. These modes are used most often for shadows and glows. Multiply mode is also useful for fixing a faded photograph. The procedure is simple. Duplicate the background, put the new layer in Multiply mode, and adjust the opacity until you get the desired effect.
‘Overlay,’ ‘Soft Light’ and ‘Hard Light modes are cool effects; I usually find them the most useful for reflections, lighting effects or shading. In each of these modes, 50% gray is transparent. ‘Color Burn’ and ‘Color Dodge’ are neat, but are rarely used. ‘Darken’ and ‘Lighten’ modes are self-explanatory. Pixels in layers set to ‘Darken’ mode will only be visible if the pixels on layers beneath are lighter in tone. ‘Lighten’ works the opposite. These can be used for glows and shadows, but don’t work as well as Multiply and Screen. ‘Difference’ and ‘Exclusion’ modes help to make that trippy-looking computer art we all know and love.
Photoshop gives you a set of tools that can be combined in countless ways to help you create the images in your mind. Using layer transparency and blending modes can give your images a depth and complexity that would be difficult to achieve otherwise.
Paul Vaughn is a freelance graphic artist, writer and web designer. If you would like to see the Graphics Guy address a specific topic email Paul Vaughn at paulv@mac.com. Color examples can be seen at www.GraphicsGuy.org.
 

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