Photoshop Blend Modes
Gary Detonnancourt
Photoshop Blend Modes
Introduction
Few users wander into the domain of “blend modes” in Photoshop although it is out there in plain sight. Any time a new layer is added its blend mode can be changed to affect a subtle or drastic change in the way it interacts with the layers below. One of the reasons for users avoiding the blend modes is the terminology associated with the tool. When you click on the blend modes drop-down menu in the layers palette, a whole bunch of options appear with little hint as to what they may do to the image. So, let us start with a general explanation of the blend mode groups and then use a few of them to better understand their uses.
Blend mode groups
In addition to the always visible “Normal” there are quite a few other blend modes. They are implicitly grouped according to their general effects. I have identified the general function of each group with the added group labels. Although Adobe uses more technical terms for them, this set of group labels is used quite often because they are more descriptive of the blend functions. For instance, the first group will serve to darken the image when possible but never lighten it. Likewise, the second group blend modes will always lighten the image but never darken it. Some blend modes are far more useful in photography and are more frequently used. Although others may have their uses in some instances, many remain on the sidelines for most users. I find the following blend modes quite useful: Multiply, Screen, Overlay, Soft Light, Color, Saturation, Luminosity. In this post, I will share with you some uses of the frequently used blend modes. By the way, in addition to the layer blend modes, Photoshop also offers Brush blend modes, Apply Image, and Calculation blend modes. We will focus only on the layer blend modes this time.
Terminology
If you read articles, books on blend modes you will come across “Source, Blend, and Result” terms quite often. Each blend mode is a mathematical function that uses the pixel level interaction between the image before a new layer is added and the new layer itself. The layer whose blend mode is under consideration is called the source, the applied blend mode is called the blend, and how the image looks after that is called the result. How the mathematical functions work is not in the scope of this post. If you are interested you can search the Internet to find the mathematical expressions and extensive writing on each function. However, in order to use the blend modes you do not need to know the underlying equation, just what the blend mode does to your image.
Quick image fixes
You can use the blend modes to quickly fix the exposure and contrast of underexposed, overexposed, and flat images. Here is how to go about it. Keep in mind that the effects of the blend mode adjustments can be localized by using layer masks and their effect can be reduced by lowering the layer opacity.
Fix underexposed image
1. Open the image in Photoshop
2. Create a duplicate layer of the background
3. Change the blend mode of the new layer to “Screen”
4. Adjust layer opacity to reduce the blend mode result if necessary
In essence, you are using the image to repair itself. Depending on the luminance values at each pixel, they will be lightened. This may fix the underexposure problem and the new layer can be duplicated to add more of the same.
Fix overexposed image
1. Open the image in Photoshop
2. Create a duplicate layer of the background
3. Change the blend mode of the new layer to “Multiply”
4. Adjust layer opacity to reduce the blend mode result if necessary
Again, depending on the luminance values at each pixel they will be proportionately darkened and this layer can be duplicated with its blend mode intact to darken the image a little more.
Fix flat images
1. Open the image in Photoshop
2. Create a duplicate layer of the background
3. Change the blend mode of the new layer to “Overlay”
4. Adjust layer opacity to reduce the blend mode result if necessary
The overlay blend mode has no impact on middle gray tones; any tonal value lighter than middle gray is proportionately lightened, and any value darker than the mid tone will be proportionately darkened. The result is an image where lights are lighter and darks are darker, in other words, it has more contrast.
Split sharpening
When using Unsharp Mask Sharpening, the white halos around the sharpened edges may be hard to control at times. Of course, one can use a layer mask and hide the halos but that will also hide the darkened edges as well. One simple solution is to do the sharpening in two separate layers instead of one. One layer will control the lightened edges and the other, darkened. Here is how we can go about it.
1. Create a merged layer on top of all the layers in the image (Shift-Ctrl-Alt-E), change the name to “Lighten” and change the blend mode to “Lighten” as well
2. Duplicate this layer (Ctrl-J), change the name to “Darken” and change the blend mode to “Darken”
3. Target the “Darken” layer, and apply your unsharp mask. This can be a bit more aggressive than the light edges in the next step since darkened edges do not pop out of the image like the lightened edges in the form of white halos. Consider the output device and apply sharpening while keeping in mind that this is only one-half of the sharpening.
4. Now, target the lighten layer and apply unsharp mask. Here you may consider using a smaller radius, lower amount, and higher threshold but don’t be too shy. While applying this sharpening you will start seeing the full sharpening effect combined with the darkened edges
5. If there are halos that are too visible, add a layer mask and mask the offending halo areas. This will only affect the lightened edges and only the areas you are masking.
There are variants of this method with greater flexibility but for an introductory post on layer blend modes, this should provide a good taste of what this powerful tool can do. We have only scratched the surface of layer blend modes. Keep thinking what else you can do with these tools and don’t forget to experiment, just for the heck of it. You can even change the blend modes of adjustment layers like curves, levels, etc. to control how the adjustment interacts with the layers below. In short, layer blend modes lets you push Photoshop to do the heavy lifting when editing your photographs.
Now, get the blender out!
A. Cemal Ekin, PhD
Kept Light Photography
http://www.keptlight.com
I retired from Providence College in 2012 as Professor Emeritus. Teaching has been a great experience, affected my photography, and how I share what I know with others. That, in turn, has helped me to learn more about photography, my photography, the art of photography.
I am an interested, curious observer, fully self-taught photographer through practice, experimentation, failures, reading and looking at photographs. I write about photography to sharpen my understanding of it. You can see my work, read my articles on a wide range of photography topics, and learn more about my photographic philosophy on my Web site.