Luminosity masks are a photographer’s secret weapon to elevating a good photo to a pixel-perfect work of art. They allow you to combine speed and precision in your post-processing work, so you can quickly and efficiently make advanced adjustments.
That may sound daunting, like you need specialized skills in order to blend exposures like a professional. I am a pro, with more than 20 years using photography as my chosen medium… and I can still remember hearing about luminosity masks for the first time and feeling at once fascinated and overwhelmed. There were so many different takes on the subject, including various Photoshop plugins and panels that can be used to automate the process of generating luminosity masks — nice, but not ultimately what I was looking for.
I was interested in gaining a deep understanding of the technique and the skills necessary to manually create the masks in Photoshop. I knew that most of the adjustments can be saved as “Actions,” so I decided to teach myself how to create my very own set of luminosity masks that could be included in my non-destructive workflow.
That was five years ago. Today I’ve taught thousands of students how to use luminosity masks to elevate their work with lighting and color to a new level of mastery.
I wrote this definitive guide to demystify Luminosity Masks and to make the technique available to any photographer who wants to leverage their powerful impact in their own artwork.
If you are familiar with Photoshop layers and masks, you should be able to easily follow the technique described in this guide. By the time you finish reading this article, you will be able to work with luminosity masks like a pro, for stunningly dynamic photographs that perfectly capture your unique artistic vision.
1.The Foundation: What are Luminosity Masks?
Understanding core principles behind the luminosity masking technique will give you confidence at every step of the process.
The concept of luminosity masking is simply a way of creating soft-edged, pixel perfect selections with seamless tonal transitions. Selections are based on specific tonal ranges in an image — they target only the brights, mid-tones or darks, allowing you to apply targeted adjustments in only these areas. That level of precision is simply not possible to obtain with any “out of the box” Photoshop selection tool. And luminosity masks can be further fine-tuned and modified exactly as any other Photoshop layer mask. Let’s start at the beginning...
1.1. Additive Color Mode
Red, green and blue are the primary colors (the additive primaries). Mixed in the proper proportions, they add up to make white. By mixing these primary colors in different proportions, almost any color can be produced.
1.2. What are RGB Channels and how do they relate to Luminosity Masks?
RGB is a default Photoshop color mode and it uses three colors or channels to reproduce any color on the screen.
[To access the “Channels” panel: Window > Channels]
By default, RGB channels’ panel displays four channels: RGB, Red, Green and Blue. The top "RGB" channel contains the three separate channels combined together: Red, Green and Blue. Now, notice that the separate channels themselves don't contain any color. They are simply grayscale tone maps for luminosity values for the specific color (red, green or blue).
The areas that are bright in the red channel indicate that there is a red color present in the image; the same goes for the green and the blue. And the areas dark in the red channel indicate that there is very little or none of the red color in the image
The areas that are darker in all 3 channels indicate the areas that are dark in the color image, pointing to the fact that none of the 3 colors are present in the image in those specific areas. And areas that are brighter in all the 3 channels indicate that those areas are bright in the color image, and they contain all the 3 colors in high intensity.
This simply reflects that the same concept applies when it comes to the red, green and blue channels as it does with "standard" masks in Photoshop - “white reveals, black conceals.”
[To get a preview of the mask: ALT+CLICK on the mask thumbnail]
1.3. How RGB channels relate to Luminosity Masks?
For every single pixel in the image, Photoshop assigns color and luminosity values. We will use the Color Picker Tool to examine how it works in practice.
[To access the “Color Picker Panel” panel: click the foreground or background color selection box displayed in the Toolbox]
Color Picker Tool
Color is created by the 3 components added together: red, green and blue.
Color is measured within the numeric range from 0-255, where 0 indicates black, and 255 indicates white. The value for the pure black is R:0, G:0, B:0. And value for pure white is R: 255, G: 255, B: 255.
Between these two opposites (white and black) you have a full spectrum of colors. The Color Picker Tool allows you to take precise readings from sampled pixels for each of the 3 color components.
Beside the color values, we can read luminosity, or brightness, values (B). Brightness is expressed in percentage. (100% - white, 0% - black);
By default, the color slider displays Hue (H); click on the radio button beside the “B” to display the full spectrum of brightness for the specific color.
Now, let’s jump back to the RGB channels panel and look at the thumbnails of individual channels — notice that the luminosity values in the red, green and blue channels are represented in grayscale graduation from white to black.
This should look familiar to you, as exactly the same principle applies to standard layer masks in Photoshop. They are composed of white, black and shades of gray.
Now, if you make a selection in luminosity values from one of the three individual channels (red, green or blue) the selection will be imprinted onto a layer mask, and that's how you get a luminosity mask. The concept sounds complex in theory, but when put in practice, it very quickly it becomes an intuitive, effortless skill.
You may ask: why bother? Is all that exertion worth the result?
Yes, it is! combined with Curves, Photoshop luminosity masks can truly transform your work in a few simple steps. Luminosity masks can be intimidating because they are a bit complex to create manually. The great news is that the complete process of creating luminosity masks can be automated with Photoshop Actions. So, with a single click, we can produce a complete set of luminosity masks ready to be transformed into pixel-perfect selections.
Read on to learn how to manually create your own set of luminosity masks without using any external plugins. Once you know how to do that, you can record the process and save it as a luminosity masks Photoshop action.
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