Blending modes: does Overlay really integrate Multiply and Screen?

[YuggothBoletus]

That’s what I read on the official documents and online video tutorials: that Overlay acts as Screen with lightness >0.5 and Multiply when <0.5. Doesn’t that mean any given color should act the same in Overlay mode to either Multiply or Screen? But I keep getting 3 results different from each other, like seen in the attachment with the same color on 3 layers set to each mode, over a base color on nomal. I don’t know if the modes aren’t supposed to be exactly the same or if it’s something with my setting.

[Studio-Kyubo]

Overlay is a combination of two blending modes: Multiply and Screen. It uses different formulas based on the lightness of the base color (the color on the layer below).

• For areas where the base color is darker (below 50% gray): Overlay applies the Multiply mode, which makes the colors darker.
• For areas where the base color is lighter (above 50% gray): Overlay applies the Screen mode, which makes the colors lighter.

Detailed Explanation

• Multiply Mode: This mode multiplies the base color by the blend color. Since multiplying by a number between 0 and 1 always results in a darker color, this mode is used to darken images.
• Screen Mode: This mode inverts both the base and blend colors, multiplies them, and then inverts the result. This results in a lighter color, hence it is used to lighten images.
• Overlay Mode: This mode combines both Multiply and Screen modes depending on the luminance of the base color. If the base color is mid-gray (50% lightness), the result is unchanged. If the base color is lighter than mid-gray, Screen is applied; if darker, Multiply is applied.

Why Results Differ

The differences you’re seeing in your results might be due to how each mode processes the colors:

• Color Values: Even if a color appears the same to the human eye, its exact RGB values can influence the outcome when different blending modes are applied.
• Gamma and Color Profiles: Different settings for gamma and color profiles can affect how colors are blended. Ensure your color management settings are consistent.
• Precision and Algorithms: Different software might implement blending modes slightly differently, leading to small variations in results.

Practical Example

Consider a base color (B) and a blend color (C):

1. Multiply: Result=B×CResult = B \times CResult=B×C
2. Screen: Result=1−(1−B)×(1−C)Result = 1 - (1 - B) \times (1 - C)Result=1−(1−B)×(1−C)
3. Overlay:

• If B<0.5B < 0.5B<0.5: Result=2×B×CResult = 2 \times B \times CResult=2×B×C
• If B≥0.5B \geq 0.5B≥0.5: Result=1−2×(1−B)×(1−C)Result = 1 - 2 \times (1 - B) \times (1 - C)Result=1−2×(1−B)×(1−C)

For instance, if B = 0.3 and C = 0.6:

• Multiply: 0.3×0.6=0.180.3 \times 0.6 = 0.180.3×0.6=0.18
• Screen: 1−(1−0.3)×(1−0.6)=0.721 - (1 - 0.3) \times (1 - 0.6) = 0.721−(1−0.3)×(1−0.6)=0.72
• Overlay: Since B<0.5B < 0.5B<0.5: 2×0.3×0.6=0.362 \times 0.3 \times 0.6 = 0.362×0.3×0.6=0.36

As seen, Overlay produces a result distinct from both Multiply and Screen due to its conditional application of the two modes.

Overlay mode does integrate aspects of Multiply and Screen, but it does so conditionally based on the luminance of the base color. This results in outputs that are contextually different from simply applying Multiply or Screen alone, leading to the varied results you observe.

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I don’t know if it was the correct answer to you your question, but I hope it will be helpful.

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K . A . B . H .

[YuggothBoletus]

Thank you! Knowing that they’re intended to be not entirely the same was already comforting, and having the formula of how it all works could be so useful for understanding digital painting in general!