What Is Luminosity Masking?

Greg Benz joins Jeff to answer the question of “What is Luminosity Masking?”

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What Is Luminosity Masking?

Luminosity masking is a way to tell Photoshop which parts of an image you want to adjust by means of selections based on brightness and darkness

Greg, the phrase “luminosity masking” itself sounds really scary and complicated.  I think a lot of photographers hear that term connected to doing really good photo processing on the computer but it sounds so difficult that they give up thinking it is too hard.  I want to give listeners and readers a simple one or two sentence definition of what luminosity masking is, hopefully something that will make it less scary and help them feel like they can do it.  With that in mind, give me a one or two sentence answer to what luminosity masking is.

Greg: Luminosity masking is one of those more advanced things you can do in Photoshop.  At least it can be. Luminosity masking is way to tell Photoshop what you want to adjust in a very smart way.  Putting the photographer in the driver’s seat to target their adjustments.

The naming of the technique is a little unfortunate because luminosity masking is more about selections than it is masks.  Selection tools are the secret language to talk to Photoshop. If you want to make the sky more colorful, Photoshop doesn’t know what pixels in the photo make up the sky.  Someday that might come, but for today selecting pixels based on how bright and dark they are is how you tell Photoshop what portion of the image is the sky. It comes from the image itself.  

Luminosity masks let you select what you want to adjust in Photoshop without hard edges.  Hard edges are the things that make images look like they have been Photoshopped. You get artifacts like halos too.  With luminosity masking you can make selections of the image based on the luminance values and it selects it in a way that is feathered so that the adjustments you make aren’t nearly as obvious.

Luminosity Masking is Like Lightroom Adjustment Brushes

Jeff: I can imagine a day when Photoshop might be able to tell what in the image is the sky with artificial intelligence and machine learning.  In fact, I think Adobe is one of the most well positioned companies in the world to make that happen. Someday we may be able to talk to the computer and ask it to select the sky or even say something like brighten or darken the sky and it will know what we are talking about.  Until then, making selections of the photo based on the brightness of the pixels is the best way to tell your computer how to do what you want to do.

Luminosity masking is a little bit like the idea of adjustment brushes in Lightroom.  With adjustment brushes in Lightroom the photographer editing a photo can paint adjustments on the screen and control where the adjustment goes.  Target the adjustment to a specific portion. As humans we can see where the sky is in the photo and paint over it with the brush in Lightroom and then adjust the brightness, darkness, colors, noise, etc.

That technique feels much easier because is it so a...