Luminosity Masking: The Light Side

Posted in Uncategorized by Scott on February 23, 2007

This is part one of a two part series on luminosity masking. The original Photoshop tutorial can be found on and is entitled: Recovering Lost Highlight Detail, by Jim Patterson. Luminosity can be utilized for a great number of color and shade adjustments. Jim covers the basics, which should give you a good idea of the types of things you can do.

virgin_snow Virgin Snow redux

Okay, onward. The image for today is another CC licensed photograph found on flickr. It was originally posted by flickr user robad0b. Thanks! Please note that I don’t actually think this photograph needs editing. I used it because it can highlight an extreme use of this technique. It is a very good photograph, and this technique is not going to make it better. It will however be good for illustrating the technique.

  1. Open your image, and make a copy of the background layer.
  2. Click Image>Mode>Decompose. Select the LAB radio button, make sure the Decompose to layers checkbox is checked and click OK.
    This will create a black and white copy of the photograph that probably looks pretty funky.
  3. In the layers dialog, you’ll see 3 layers A, B and L. We only want the L (luminosity) layer, so you may discard the other two.
  4. Select the entire layer (Ctrl-A) and copy it (Ctrl-C).
  5. Go back to the original photograph. Right-click the background copy layer and select Add layer mask. Initialize it to white (full opacity) and click OK. Now, paste the copied luminosity layer from the decomposed version onto this mask (Ctrl-V). Anchor the layer by right-clicking the floating selection and selecting Anchor layer. You should now have a black and white thumbnail next to the color thumbnail in the background copy layer.
  6. Now, we don’t want to affect the sky with our luminosity adjustments, so we’re going to mask it out by painting black over it on the mask. Right click the Background copy layer, and select Show layer mask. Use a soft brush, and carefully go over the edges of the sky with black.
    Now you can either continue using the paintbrush, or use the freehand select tool to select the rest of the sky and fill it in with black.
  7. The mask is now prepared, so on your layers dialog, right click the Background copy layer and select Apply layer mask. Here is what my masked layer looks like.
  8. Now for the adjustments. First thing, make sure Background copy layer is selected and change the layer mode to Multiply. Right away you will notice a big difference.
  9. The next few steps are really subjective. Here’s what I’m going to do. First I’ll reduce the opacity of the Background copy layer to around 50%. Then I went to Layer>Colors>Curves and bumped up the Value just a bit. Now, the rocks are too dark, so I’m going to erase the rocks from the Background copy layer using the eraser tool.

virgin_snow done
Now, you’ll notice the area below and to the right of the rocks has a bit more detail, and the shadows are much more defined. I hope you’ve enjoyed this tutorial adaptation. Next time we’ll finish up with The Dark Side.

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