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I'm trying to understand how luminosity blend mode works in graphic design. Wikipedia says:

https://en.wikipedia.org/wiki/Blend_modes#Hue.2C_saturation_and_luminosity

The Luminosity blend mode preserves the hue and chroma of the bottom layer, while adopting the luma of the top layer.

https://www.photoshopessentials.com/photo-editing/layer-blend-modes/luminosity/


There's also an article here:

https://www.photoshopessentials.com/photo-editing/layer-blend-modes/luminosity/

Our fifth and final essential blend mode for photo editing in Photoshop is Luminosity. Like the Color mode, Luminosity is found in the Composite group of blend modes along with Hue and Saturation, and is actually the exact opposite of the Color mode. Whereas the Color mode blends the colors of a layer while ignoring lightness values, the Luminosity mode blends the lightness values while ignoring the color information!


These explanations don't really make too much sense to me, as I don't have a strong background in Graphic Design and Photoshop, but I'd like to understand the ins and outs of it.

Could someone explain it perhaps in simpler terms and with a concrete example? Thank you very much!

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  • Hi. IMHO the best way to understand it is probably to try using it, to experiment, to play around with the blend mode using various images on different layers, to see what effect it produces. If you are not familiar with these terms, then descriptions like this will just look like word salad.
    – Billy Kerr
    Nov 1, 2023 at 17:58

1 Answer 1

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There are different color models. They are 3D representations of the coordinates of different colors but using different axis and values.

RGB uses 3 linear axis. But some other uses 2 linear axis and one angular. The angular one is HUE.

There are different models and interpretations of how to grade the linear, for example, lightness vs. brightness.

Here are the channels (HSL) of a simple chromatic circle.

enter image description here

And here of a photo. The channel that is less abstract is the luminosity one.

enter image description here

According to the first description you posted, the Luminosity blending mode is using this channel to replace the values of the layer below.


Now some tests. I added a tiny diagram to the left of each so you can see which is over which and if it has Luminosity (L) or Color (C) blending modes.

The text says that the Luminosity Blending mode is the opposite of the color mode.

(A) The one on the left has the girl as Luminosity. You can see that the photo is only grayscale because is only a channel and is on top of the color wheel.

(B) The one on the right has the color wheel on top of the girl with color blending mode, and you can see that the girl's photo (hat) is in normal color (not grayscale)

The result is the same with the layers inverted. Girl-Wheel, Wheel-Girl.

enter image description here

There are differences in how software interprets the channels, even if they are called the same, so the result may vary.


Take a look at another post, where I try to compare some blending modes with real-life color manipulations.

Image: https://www.pexels.com/es-es/foto/foto-retrato-de-mujer-con-lapiz-labial-rojo-y-sombrero-rojo-boina-posando-2816544/


Edition based on the comment.

(C) The circle on the left is the one I used, and you can see that the "darkness" (lightness) is overridden by the luminosity of the photo. The dark center is no more dark.

(D) On the right circle, the color of the circle is affecting, not the darkness (anti luminosity). You can even see that the circle is not dark at all. It is not showing its luminosity anymore.

enter image description here

will appear as grayscale only when it is on top of the other layer

The "other layer" is a circle with a white background, so it is gray on the zones with no "color" meaning a white background.

If it is on the bottom of another layer... you will not see it. It is behind... but something should be behind, probably your checkerboard background or something. There is always something behind it.

A blending mode is always the layer with the mode over another layer. This other layer can have or not another blending mode, but that is a separate thing.

Here is a screen capture of the program I'm using. I sent the layers that have the effect to the back. The photo on the left and the circle on the right. (F) You can see that now the circle is affecting the background gray and the white paper. The luminosity.

On the tiny corner of the left photo (E) , you can see it looks normal because it is only a luminosity, over a white and gray luminosity paper. So the photo is overriding that.

enter image description here

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  • Thanks for the explanation. I'm trying to get to the grips with it. Does this mean that for Luminosity Blend Mode the layer on which this blend mode is applied will appear as grayscale only when it is on top of the other layer and only for the parts where the two layers don't overlap? Is that how it works?
    – tonix
    Nov 2, 2023 at 17:39
  • Grayscale if the background part is white. As it is white it will not be modified. Let me add a new example with a different background.
    – Rafael
    Nov 2, 2023 at 19:58
  • I edited the answer. I hope it helps.
    – Rafael
    Nov 2, 2023 at 20:41
  • Thank you for your detailed answer @Rafael! I'm trying to understand all your examples, as I don't have any background in graphic design. I find it a bit difficult to understand how everything relates to each other.
    – tonix
    Nov 3, 2023 at 18:22
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    Ask if you need additional clarification.
    – Rafael
    Nov 3, 2023 at 20:31

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