Luminosity masking is pretty simple but very effective! Up to here we have learnt to mask manually with the brush and marquee tools, we created masks by colors, and in the previous post we used the channels for masking. But what about using the degrees of brightness in the image to create a high precision mask?
Create Luminosity Masks Manually
Open an image in Photoshop and switch from the layers tab to the channels tab (as described in the previous tutorials in more detail). Then press the keys Ctrl+Alt+2 together and voila, the ants indicating a selection in the image start marching.
Switch back to the layers tab and add an adjustment layer of your choice. A pretty sophisticated mask will automatically be added to the layer.
Tipp: Keep in mind, the darker a part of the mask the less the layer effect will be applied there. In black parts of the mask the effect of the layer will be blocked totally, in white parts it will be fully applied. Please read back my previous masking tutorials, if this sounds all geek to you.
Simply spoken we have now selected all lighter areas in the image. That’s just half true. We actually have made a selection on the level of brightness in each pixel. A brighter part of the image is masked less strong than a darker part of the image.
The effect of your adjustment layer therefore will be applied stronger the brighter an area in your image is, and less and less the darker the area is. Approximately we can say to have selected the brighter parts of an image.
Tipp: You think it’s not a big deal yet? This mask can be very useful when sharpening an image. Often we want to sharpen more in the highlights than in the darks to avoid noise. Well, duplicate the layer of sharpening in your image with Ctrl+J, apply the lights mask as shown above to one sharpening layer, copy the mask (Alt+drag and drop) to the other sharpening layer, and invert the mask there for targeting the darks instead.
You now should have two identical (duplicated) layers for sharpening, one targeting the lighter parts of the image and blocking the darks, the other one working in the exactly opposite direction. With the opacity slider then dial in the amount of sharpening in both layers for each parts of the image lights and darks.
If you want to use a light mask more than once simply save it in the channels tab. After a selection is made before switching to the layers tab, first click on the “Save selection as channel” icon in the bottom (the rectangle with the little hole). Rename the new channel to “Lights”.
Tipp: If the selection disappears and you want to load the selection of a channel again, Ctrl+click with the mouse on the channel to load, for example the newly created “Lights” channel.
Ok, but there is more, of course. Selecting the upper half of brightness and blocking the darker half cannot be all yet. Let’s try to target the very bright lights only.
Iterations of Luminosity Masks
In case you are already back to the layers tab delete the layer with the first light mask which was just created and switch back to the channels tab. Make sure to select the RGB channel by clicking it once.
Start with the same procedure as before to select the light pixels by Ctrl+Alt+2. But now we want to go one step further, just selecting the even lighter pixels out of this selection. This will require a bit of fingers gymnastics, at least on my keyboard.
After the first selection is made hold Shift+Ctrl+Alt and simultaneously click with the mouse on the RGB layer again. You will see the selection of marching ants narrows down to the even brighter parts only. Save the mask as a new channel (rectangular icon with hole in the bottom) and rename the channel to “Light Lights”.
One more? Ok, make your way as described to create the Light Lights selection. Instead of saving it do the finger-yoga again by holding Shift+Ctrl+Alt and simultaneously clicking on the RGB layer. The selection will be narrowed down even further. Save it as “Bright Lights” or “Light Light Lights”
Feel free to add as many iterations as you think to need for your post-processing.
The Dark Side of Masking
But what to do in case we want to target the darks instead of the lights?
Very simple! Create a lights channel as described above and invert the mask by clicking it and pressing Ctrl+i afterwards. Rename the channel to “Darks”. Done.
For loading the mask Ctrl+click the channel (the marching ants appear), switch to the layers tab and add a new adjustment layer of your choice. Automatically the selection of darks will be added as a mask.
For the even darker darks back in the channels tab create a lights channel, invert it (Ctrl+i) to be a selection of darks, load the selection with Ctrl+click on the layer, and press Shift+Ctrl while clicking on the layer with the mouse again and again for each iteration.
After the first iteration save the selection (rectangle with hole icon in the bottom) and rename it “Dark Darks”. Next iterations were “Shadow Darks” and “Super Darks”. Again, add as many iterations as you think to need for the specific image.
Tony Kuyper Masks
If you want to read deeper into the technique, combining and subtracting masks from each other, check out Tony Kuyper’s website for luminosity masks, he’s the real guru for this technique! Or even better, check out my earlier post “My Favorite Little Photoshop Helpers” and purchase Tony’s fantastic tool for quickly creating any luminosity mask you prefer with a simple mouse click.
When to Use Luminosity Masks
There are plenty of situations luminosity masks in Photoshop will help you target specific areas of the image in a different strength.
As noted above the simple lights and darks masks can be used to apply sharpening in a different amount to the lights and the darks in the image.
Sometimes you might only want to work on a specific brightness range in the image with increasing color saturation instead of pouring a bucket of saturation all over the image.
Another time you will want to reduce ugly noise from the blacks in your image only.
There are literally thousands of ideas when to use this masking technique.
For me it’s a tool used kind of daily.