Luminosity Masking Basics

Listen to the Image
As you look at an image, ask “What Can I Do to Improve This Image?” The human eye is attracted to lighter areas and to contrast. How can I adjust this particular image to guide the viewer’s eye?
I suggest you use adjustment layers for any type of tonal modification! The key; adjustment layers are not permanent. Each adjustment dialogue can be reopened at any time to revisit changes you made. You can change opacity slider, blending modes, layer masks, or luminosity masks. Each change precisely focuses the correction to specific image areas.
Blending modes influence how a color or tone interacts with the color or tone beneath it. This interaction may differ based on image brightness values; it also occurs on a per channel basis. Blending modes can be broken into darkening, lightning, contrast enhancement, and finally component control.
Use overlay for soft light to increase contrast works best on images that are too flat and like good contrast.

What’s in a Raw File?
No matter what the photographer shoots, his raw file simply records the luminance value for each pixel. So the raw file is a grayscale image. It contains color information.
Raw converters obtain a color image from that raw file. They apply tone mapping to redistribute the tonal information. They ‘convert’ grayscale so our eye can see light and shade.
In photography, tone refers to the brightness level (luminosity). This is true for both black-and-white and color photographs. A photo is made of many different brightness values. It’s the specific brightness value arrangement per pixel that gives shape and form to an image. The most common terms used to describe tonal values refer to 3 categories of brightness; shadows, midtones, and highlights. Within each of 3 areas, there are many different tonal levels. The foundation for creating the image you want – learning how to work with the entire tonal range through luminosity masks!
Contrast is a challenging element in photography. Put simply, contrast is difference. It’s the difference between tonal values. The greater the difference in brightness between tonal regions, the more contrast. Increasing contrast requires making light tones brighter. Decreasing contrast makes dark tones darker.

Luminosity Masks
The mask rule is “white reveals and black conceals.” Pure white allows matching pixels on the layer to be completely visible in the image. Pure black blocks related layer pixels from appearing in the image. The blocking effect of black in the mask only occurs on the layer to which the mask is applied. If pixels are blocked from appearing on one layer, Photoshop sequentially looks down to layers below to find unblocked pixels it can display.
Shades of gray in a mask allow image pixels to appear in proportion to how light or how dark the gray value is. A 50% gray mask allows your layer pixels to be visible at half normal opacity. Darker gray values in the mask allow proportionally less of the layer to show and lighter gray values proportionally more.
Let’s take a closer look at a “Lights” luminosity mask. By clicking on the thumbnail image of “Lights” channel or the word “Lights” (right of thumbnail), the mask itself is now visible on main image area in Photoshop. The Luminosity Mask is a perfect grayscale positive of the image. It has very little pure white or black. It also has shades of gray that perfectly mirror image brightness values. When applied to an adjustment layer, it will reveal adjustment effects most on brightest image pixels in the light pixels (white reveals) and less as pixels get darker (black conceals).
This leads to a most important luminosity mask property: they are completely self-feathering. The image effect will be obvious. But there will be no way to tell where that effect begins or ends. There are no hard edges and no need to try and make a perfect selection. Because the luminosity mask was created from the image itself, it has the perfect gradation of shades to insure each and every pixel will be affected in exact proportion to its brightness.

Photoshop Mask Comparison
To appreciate the usefulness of this mask and other luminosity masks, it’s important to know exactly what masks are and how they work. Photoshop selections are normally created using Quick Select and Lasso tools. Typically these tools create pure black and white masks. When you hit the “Save selection” button on Channels palette after using each tool, the mask would is filled only with pure black and pure white with sharply defined edges. Subsequent blurring, feathering, and anti-aliasing can introduce some gray tones for a less abrupt transition, but for the most part, this Photoshop mask remains mostly all black and white.
There are no hard edges like with Photoshop’s selection tools. There’s no need to try and make a perfect selection. Because the luminosity mask was created from the image, it has perfect gradation of shades to insure each and every pixel is affected in exact proportion to its brightness.

What Should I Know to Use Luminosity Masks?
Luminosity masks are for intermediate to advanced Photoshop users. A working knowledge of channels, blend modes, actions, adjustment layers, and properties smooth’s the transition to creating fine art magic.

Tone Mapping of Luminosity Masks
Tony Kuyper separates luminosity masks into 3 basic categories; curves, levels, and channels. Each of those categories has lights, mid tones, and darks.
With an image open, you ‘listen to it…’!
You ask ‘what are strong or weak points of this image?’ You then tailor curves, levels, hue saturation, color balance, and vibrance as luminosity mask layers. By opening each layers Properties panel, you can modify layer parameters to change how the original image will be seen by the viewer.
In effect, you can do subtle painting over the entire image – strengthening the strong points and diminishing the weaker points. This subtle painting on luminosity masks leads the viewer’s eye to create strong impact.

About Joe 

Photographer, author, teacher with enhanced skill creating Award-Winning Photos. Joe uses Luminosity Masking and CFAM-Creating Fine Art Magic for his work!