The Trouble With Normal
By Mike Pasini, Editor
Imaging Resource Newsletter
In a word, it's boring. Same old same old. Yadda yadda.
There's a spectacular world of special effects (and handy corrections) tucked
away in your image editor's blend modes. Normal is the one you already know
Launch your image editor. Open an image. It's on a layer. Create a new layer and you've got two layers, the new one (which may have nothing at all) on top of the original image. A base, an overlay. Two layers.
The layer on top is the blending layer. By definition. But that's where it gets interesting.
Given any two pixels -- one on the bottom layer, one on the top or blending layer -- what happens? How exactly are they blended into the final pixel you see in the image?
Lots of ways. Which is where your blending mode comes in. So let's see what each mode (the exact name may vary by application) does with the base color (the original color of the bottom layer pixel) and the blend color (the pixel in the blend layer) to get a resulting color (the final pixel).
A particular pixel may be said to have three dimensions: hue, saturation and luminance. Hue is color (red, green, blue). Saturation is the intensity of the hue (bright red, dull pink). Luminance is brightness (what the color would look like in gray).
Say you just want to change the color of your in-law's block sweater to, perhaps, your alma mater's colors. Simple. Just duplicate the layer, select the sweater in the duplicate layer, set your foreground color to your preferred color, set the layers blending option to Hue, then fill in the selection by clicking inside it with the Paint Bucket (or similar) fill tool. Just the color of the sweater will change.
Now let's look at the effects of various blending options in groups (using the Photoshop Layers Blend pull-down menu as an example). Following the same steps as above, try each of the following Blend options (make sure you go back to the original color before each change):
Normal & Dissolve
- Normal: (Default setting) The result color is the blend color, which you can modify only by changing the opacity of the blend layer.
- Dissolve: The result color is the blend color just like Normal, but as you modify the opacity of the blend layer, blend-layer pixels are removed, so you get a speckled effect nothing like Normal.
Multiply, Screen, Overlay, Soft & Hard Light
- Multiply: The result color is the base color multiplied by the blend color, creating a darker color. Multiplying by black always results in black. Multiplying by white doesn't change the color. Like felt pens, each stroke deepens the color if the blend color is anything but black and white.
- Screen: The result color is always lighter after multiplying the inverse of the blend and base colors. So black leaves the color unchanged while white always results in white. Think of "screening" in this context like a screen door: blocking stuff (like black flies) out.
- Overlay: The result color is either Multiplied or Screened, depending on the base color. Dark base colors are Multiplied and light base colors are Screened, preserving the base highlights and shadows.
- Soft Light: The result color is a lighter base color if the blend color is lighter than 50 percent gray and a darker one if it is darker. If the blend color is black or white, it only darkens or lightens the base color.
- Hard Light: Like soft light, except a black blend color can end up a black result color and a white blend color can paint white. Handy for adding either shadows or highlights to an image.
Dodge & Burn
These guys aren't available in LAB mode.
- Color Dodge: Brightens the base color to reflect the blend color.
- Color Burn: Darkens the base color to reflect the blend color.
Dark & Light
These guys aren't available in LAB mode either.
- Darken: The result color is the darker of the base or blend colors.
- Lighten: The result color is the lighter of the base and blend colors.
- Difference: The result color is what's left when the brighter color is subtracted from the darker color, regardless of layer. If the blend color is white, the base color is inverted. If it's black, the base color is unchanged.
- Exclusion: The result color is slightly lower contrast but similar to Difference.
Hue, Saturation, Color & Luminosity
- Hue: The result color has the hue of the blend color and the luminance and saturation of the base color. Hue only.
- Saturation: The result color has the saturation of the blend color but the hue and luminance of the base color. Saturation only.
- Color: The result color has the luminance of the base color with the hue and saturation of the blend color. Gray levels are preserved while allowing them to be tinted, as in a hand-painted black-and-white image. Hue and saturation.
- Luminosity or Luminance: The result color has the hue and saturation of the base color but the brightness of the blend color. Brightness only.
What you put on a blend layer is the fun part (the X-Factor). It can be anything
from a duplicate of the image to a flat color fill. The possibilities are, well,
For example, if you want to increase density evenly across your image, create a new layer, fill it with black, and Multiply. Now do it again and scale back the opacity until you get a result you like.
If you want to increase density more in the shadows than the highlights, duplicate the image in the blend layer, desaturate it to a black-and-white image and again choose Multiply. You can alter the blend layer image with Levels to modify the effect even further.
And if you want to increase saturation at the same time, don't bother desaturating.
If underexposure is the problem, try using Screen instead of Multiply. Reduce the opacity until you have just the right overall density.
Experiment with the other blending modes as well. You may wander off looking for a correction, only to find a special effect.
Remember that you can fine-tune an image by working on just a selection in the blend layer. And just as you can reduce an effect with the opacity setting, you can redouble it by flattening the blend layer into the base layer and creating yet another blend layer.
For an example of using blend modes in the real world, take a look at our recent
article "Fixing Flash Fall-Off" at http://www.imaging-resource.com/IRNEWS/archive/v02/20000602.htm#adv.
Count On It
It's worth experimenting with your image editor's blend modes, particularly when you get the unmistakable feeling you're working too hard to get a particular effect. There's usually more than one way to accomplish something in image editing -- and often the best answer is just using the right blend mode.
This article is reprinted from The Imaging Resource Digital Photography Newsletter,
Advanced Mode Column, published December 8, 2000
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