Blending Modes part 5: Solarization


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Doug
Blending Modes part 5: Solarization

We're down to the final two blending modes: Negation and Exclusion. I haven't found any value to these blending modes aside from producing solarization effects. I'm not really familiar with what solarization should look like, so I can't say how effective they are at that task. Here's an example of solarization being used to change the skies, and it's probably the only digitally-solarized image I've ever liked.

These two blending modes are closely related. Both result in negative contrast at brighter tool output levels. They're a bit funky because — like Hard Light — they're mask-oriented and their behavior at each pixel (and each channel of each pixel) is controlled by the tool output level rather than by the original image level. Both are probably easier to deal with when the tool has no effect, such as a Hue/Saturation tool with all sliders left at zero. In that case only the magenta line in the charts below matters.

If used on a Hue/Saturation tool, adjusting the Luminosity slider can allow you to move between the lines, thus changing the reversal point. Of course, it'll affect the brightness of the resulting image, perhaps requiring another Hue/Saturation tool to compensate.

Negation

This blending mode produces hard solarization, with an abrupt transition from positive contrast to negative contrast.

Light Crafts says: "This blending mode is similar to the Exclusion blending mode except that it shows brighter and more vibrant colors." That's a very creative explanation, if not particularly helpful.

Through most of the brightness range, the image is lightened by one stop and the tool effectiveness is cut in half. But above the point at which the tool output reaches the limit, strong negative contrast is applied. The different reversal points and different slopes depending on the original level and the tool output level make this blending mode very disruptive on bright colors.

Other than solarization, I don't know of any reasonable use for this blending mode.

Caution: this blending mode is applied on a channel-by-channel basis. This can very easily result in some wild color shifts in the brighter areas.

Exclusion

This blending mode is pretty much a watered-down relative of Negation, where the contrast rolls off between positive and negative instead of making an abrupt reversal. Overall contrast is significantly reduced because shadows are lightened by one stop while the blended output never reaches white and, in fact, almost never even reaches the brightest stop — so you lose one stop on the dark end and one stop on the bright end — and the slope is reduced through the mid-tones.

Light Crafts says: "Creates an effect similar to, but lower in contrast than, the Difference blending mode." They can't really think that, can they?

Through most of the brightness range, the image is lightened by one stop and the tool effectiveness is cut in half. Both the lightening and the tool effectiveness are reduced to zero for original-pixel levels of 50%. Above the point at which the tool output reaches 50% (one stop below maximum), contrast is greatly reduced and consequently the blended output barely goes about 50%. When the tool output reaches maximum, strong negative contrast is applied, although a darker tool output will reduce the strength. The different change points and different slopes depending on the original level and the tool output level make this blending mode very disruptive on bright colors.

Other than solarization, I don't know of any reasonable use for this blending mode.

Caution: this blending mode is applied on a channel-by-channel basis. This can very easily result in some wild color shifts in the brighter areas.