Everyone knows that 2 x 2 =4.
How about: red x green = ?
Well, the answer actually depends on the value (lightness/darkness) of the red and green used, when you’re dealing with Multiply Mode in Photoshop.
Multiply Mode, according to Photoshop help:
Looks at the color information in each channel and multiplies the base color by the blend color. The result color is always a darker color. Multiplying any color with black produces black. Multiplying any color with white leaves the color unchanged. When you’re painting with a color other than black or white, successive strokes with a painting tool produce progressively darker colors. The effect is similar to drawing on the image with multiple magic markers.
Let’s get to some examples.
When you have a grayscale layer set to Multiply, the results are pretty predictable. Black areas will remain black; white areas will be transparent and allow the base layers to show through; grey areas will have partial opacity. In this example, I’ll start with a greyscale pawprint, then set the layer to “Multiply” over another image:
Now, I don’t pretend to fully understand exactly how the Multiply Mode works when it comes to blending colors — I kind of get it, but I wouldn’t be able to predict what the end result of blending two images or colors would look like to great detail. You’ll probably find as well that it’s just going to take some experimentation. Maybe this example will help:
Take the original image of the dog, plus a rainbow pawprint. Set the pawprint to Multiply mode, and here’s the result — kind of like a “clear rainbow plastic” effect, but that the result colors are slightly darker, as well:
Okay, now for the practical applications. I have two:
1. Darken pictures.
This application is sometimes useful. In particular, when you have a slightly overexposed photo (think “washed out”), you can duplicate the photo on a new layer and set it to multiply, then play with the opacity level of the new layer until you feel the darker values are adequately … dark.
Here’s my original dog picture:
I’ll duplicate the layer, set it to Multiply mode, and change the opacity to 40 or 50%:
Here’s the result; while the light areas haven’t been too affected, the darker areas are definitely a little darker:
(download example .psd file for dog examples)
(Side note: I would probably play with the Saturation, Levels, or Curves to put more “oomph” into the final image.)
On to the next practical application…
2. Color line drawings.
This is probably one of my most-used blending mode applications. Because Multiply Mode works where black areas are black, and white areas transparent, it is ideal for “coloring” black and white line drawings.
I’ll start with a scanned line drawing:
I’ll set that layer to Multiply Mode, then add another layer underneath. As I paint (in color) on the bottom layer, the colors show through!
The beauty of this method is that you don’t have to worry about losing detail on the line drawing, as you don’t touch that layer at all. (Contrast this with using the paint bucket or paintbrush tools, where inevitably some of the pixels will be lost from the line drawing.) As you can see from this snapshot of the bottom layer, I wasn’t overly careful with the color edges:
Here’s my final image, in color:
(download example. psd file)
Now, I bet you can think of more ways to use Multiply Mode to your advantage. For example, the line art technique would work just as well with “colorizing” black and white photos. Feel free to share other neat ways of using Multiply Mode by adding a comment!