In photo editing, luminance means the brightness of a pixel, separate from its color. Photoshop uses this idea in several places, most notably in luminosity masks, which let you select and adjust a photo based on how light or dark each area is. This guide explains the terms and walks through the basic technique. Menu names and shortcuts vary by version, so confirm them in your copy.
Luminance and luminosity: the terms
The words are used loosely, so it helps to separate the meanings:
- Luminance is the brightness information in an image.
- Luminosity masks are masks built from that brightness information.
- Luminosity blend mode applies only the brightness of a layer to the layers below, ignoring its color.
- Luminance sliders in Lightroom and Camera Raw adjust the brightness of specific color ranges.
What is a luminosity mask
A luminosity mask is a layer mask in which brighter pixels are more selected (or less, if inverted). Because the selection follows the image’s tones, edges are naturally soft, and adjustments blend smoothly without the halos hand-drawn masks can create. You can create masks that target highlights, midtones or shadows, often in several strengths such as “lights,” “brighter lights” and “darks.”
Making a basic luminosity mask
One common method:
- Open the image and make sure the Channels panel is visible.
- Ctrl-click (Windows) or Cmd-click (Mac) the RGB composite channel thumbnail. This loads a selection based on brightness. Photoshop also has a keyboard shortcut for this; check the shortcut list for your version.
- Add an adjustment layer, such as Curves or Levels. The active selection becomes the layer’s mask.
- Adjust the curve and watch the effect confined to bright areas. Choose Select > Inverse before creating the layer if you want the darks instead.
To get a midtone mask or narrower ranges, photographers subtract or intersect selections or use actions and panels made for the purpose. A beginner can start with the simple lights and darks versions.
Using luminosity masks
- Recover highlights: pull down a Curves adjustment through a lights mask to restore sky detail.
- Open shadows: lift a Curves or Exposure adjustment through a darks mask.
- Dodge and burn: use midtone masks for gentle, targeted lightening and darkening.
- Color toning: apply color balance to just the shadows or highlights.
Keep adjustments modest. Heavy edits through a mask can cause banding or noise to show up, and you can reduce harshness by blurring the mask slightly or lowering the layer opacity. For other non-destructive approaches, see smart filters in Photoshop.
Luminosity blend mode and range masks
Setting an adjustment layer’s blend mode to Luminosity applies the change to brightness only, which can stop a Curves adjustment from shifting colors. Camera Raw and recent versions of Photoshop and Lightroom also include a Luminance Range masking option for local adjustments, which creates a similar effect with a slider rather than channel selections. Availability depends on your version.
Luminance in Lightroom
In Lightroom’s color mixer and in the noise reduction panel, “Luminance” means different things. In the color mixer, the Luminance sliders change how bright a color range appears (for example darkening blues to deepen a sky). In Detail, the Luminance noise slider reduces brightness noise. They share a name but do different jobs.
Brightness and contrast in Photoshop
For quick changes, Photoshop includes Brightness/Contrast, but Curves and Levels offer much finer control. Many editors prefer adjustment layers because they are reversible. Combining those with masks gives the control luminosity masks provide.
FAQ
What are the two types of masks in Photoshop? Layer masks (which hide or reveal part of a layer using black and white) and vector masks (which use shapes and paths). Clipping masks and others also exist.
Is a luminosity mask destructive? No, when it is used on an adjustment layer.
Are luminosity masks required? No. They are one of several ways to edit tones selectively. Our overview of editing apps lists other tools with masking.