The blending modes in Adobe Photoshop offer countless possibilities for creatively transforming your photos, as well as providing practical solutions to some real world imaging problems that may crop up from time to time. In the 2nd edition of Photoshop Masking & Compositing, which I co-authored with Katrin Eismann & James Porto (Peachpit Press, 2012), we cover the blending modes and how they can be used for creative effects when making collages. There are 26 blending modes available in the Layers panel in Photoshop CS6, some more useful than others. In this article I want to focus on two of the blending modes that can be very useful for creating multiple image composites: Multiply and Screen.
The key to using Multiply and Screen, as well as several other blend modes, is that each of these blending modes has a neutral color, a color that is “invisible” to the blending mode, and therefore hidden in the final result. Knowing what a blend mode’s neutral color is, and creating layers to take advantage of this, allow for quick and simple composites. Let’s take a look at some examples.
Combining two images using the Multiply blending mode is a bit like sandwiching two 35mm slides together and viewing them on a light box (for those who remember what slides are!); you can see parts of both images, but the overall result is darker than either of the source images, as seen in the illustration below of the sunset sky and the palace.
Multiply emphasizes the darker areas of each layer. This makes it useful for blending a darker subject into a lighter background, while still retaining the effect of partial transparency. The neutral color for Multiply (as well as for Darken, Color Burn, Linear Burn, and Darker Color) is White. Areas of pure white on the active layer will be hidden when these blend modes are used. Even if you don’t have total white, lighter areas will show through very little, while darker areas will be very visible. You can see this concept in action in the illustration below. The overexposed areas of the cathedral image become hidden when the blend mode for that layer is set to Multiply, allowing the sky image from underneath to show through.
In the example below from Photoshop Masking & Compositing, the image of the old ship’s log is added as a layer to the sailing ship photo. With the logbook layer set to Multiply, the darker writing shows through because it is much darker than the cloudy sky and ocean below it. The Multiply blending mode is excellent any time you want to blend images of old letters, postcards or documents into an image because the light areas of the page do not show up much, while the darker writing does.
In the image below, also from the Photoshop Masking & Compositing book, using Multiply on the photo of the crows flying against a light sky blends the dark birds perfectly into the clock tower composite below.
The Screen blending mode is the opposite of Multiply. Lighter areas are emphasized over darker ones. To return to the 35mm slide analogy, combining two images with the Screen blend mode is a bit like having two slide projectors each showing an image on the same screen. You can see both images blended together but the overall effect is much lighter than either of the source images, as seen in the illustration below.
The neutral color for Screen (as well as Lighten, Color Dodge, Linear Dodge (Add), and Lighter Color) is black, which will be totally hidden when a layer is set to Screen. This can be used to good effect when blending transparent glass in a composite. If the glass item is photographed against black, only the lighter reflections will show in the composite. You can see this in the image below of the glass dome over an Icelandic mountain. This composite was actually created entirely on an iPhone, which is why there is no Photoshop Layers panel in the illustration. The composite was made using Filterstorm, an excellent app which offers many of the same blending modes and masking functionality found in Photoshop.
Since screen reveals lighter areas but does not show darker parts of the layer, the most effective uses for it in terms of composites is when you have an image with lighter details on a very dark background. The Screen blend mode does an excellent job of seamlessly blending such an image into another photo, as seen in the combination of a NASA image of deep space with typical window seat view on a commercial passenger jet.
To make the most of the functionality that blending modes offers, whether for composites or other projects, learn the basic “rules” of the blending mode, become familiar with how it acts on different types of images, and then experiment and have fun. I’ll be covering additional compositing techniques in future columns.