Painted Masks

NOTE: A more complete description of this mask painting technique can be found here.

Luminosity painting is one of my favorite Photoshop techniques and is described in a this tutorial. It is a method for burning (darkening) and dodging (lightening) specific areas of an image and specific tones in those areas by painting through luminosity selections.

Painting a layer mask for an adjustment layer is another example on how luminosity painting can be used. It provides a method to first make a global adjustment using an adjustment layer, then hiding it, and then painting to very precisely reveal the adjustment in exact areas and tones in the image.

The image below shows the final version of an image where an adjustment layer with a painted luminosity mask played an important role during development. The mouse rollover is the image with this adjustment layer’s visibility turned off. (It may take a few moments for the second image to load, but once it does, you should be able to pass the mouse back and forth across the edge of the frame to flip between the before and after image.)

Essentially what is happening is that an adjustment layer is affecting the image (darkening it), but only in specific tones and in specific areas. All similar tones are not equally affected, as would be expected with a specific luminosity mask serving as a layer mask for the adjustment. In fact, no single luminosity mask is able to mask the adjustment with the accuracy needed for this particular image. A painted mask, however, is able to do this with relative ease. It augments a luminosity selection to over-reveal the adjustment in some parts of the image, completely conceal the adjustment in others, and even incorporates parts of two different luminosity selections into the same painted mask. In this way, painted masks allow greater customization depending on what the image needs.

To make this adjustment, I started by first creating a Curves adjustment layer and changing the blending mode to Multiply. Multiply blending mode is like placing two identical transparencies in register on a light box. Even though each may be properly exposed, stacking one on top of the other makes the image look much darker, as if it were noticeably underexposed. In a similar way, Multiply blending mode darkens an image except that pure white (255,255,255) and pure black (0,0,0) are unchanged. Below is how the image looked after doing this.

While clearly excessive when not moderated by a mask or decreased layer opacity, Multiply (and its image-lightening counterpart, Screen) blending mode tend to make very natural-looking tonal changes to the image when properly applied. Provided that they are used in moderation, these blending modes can subtly and appropriately change image tones without unexpected saturation or contrast changes that sometimes accompany Curves and Levels adjustments.

By default, Photoshop creates an all-white, reveal-all layer mask when adjustment layers are created. Once the blending mode is changed to Multiply, the image is clearly too dark because the pure white mask conceals nothing. While Multiply blending mode will benefit parts of the image eventually, this full-on effect is not desired. To return the image to its original state before the adjustment layer was added, simply type Ctrl+I (Mac: Cmd+I) to invert the layer mask from white to black. This completely hides the adjustment from the image. The menu command Image>Adjustments>Invert can also be used to do this. The figure below shows how the new layer looks on the Layers panel. It’s worth noting that no adjustment was made to the curve for this adjustment layer. Changing the blending mode from Normal to Multiply is all that was needed to darken the image.

Once the desired (but exaggerated) adjustment is created and concealed, it’s necessary to create a luminosity selection to paint through to reveal the concealed adjustment just where it’s needed in the image. The easiest way to get the right selection to paint through is to make an entire series of masks on the Channels panel and choose what works best. For this image, I want to darken some of the lighter tones in the image. The Lights-series of luminosity masks provides several choices of masks that target progressively lighter tones. The figure below shows this series of masks as they appear on the Channels panel.

Masks are graphical representations of selections, with light colors showing selected pixels and black representing pixels that aren’t selected. Shades of gray correspond to the degree to which pixels are selected—dark gray pixels are less selected than light gray pixels. Any mask can be turned into a selection with a Ctrl+click (Mac: Cmd+click) on the mask’s thumbnail image.

Examining the masks by clicking them one-by-one on the Channels panel helps find the most appropriate one for this image. The mask that shows white (or light gray) in the areas that need to be changed (darkened in this case) is a good starting point. However, it’s also good to think about combining masks to make an even more refined selection to paint through. For most selections I use for luminosity painting, I’ll generally subtract off a selection at the extreme end of the series. So, for example, in this case I chose the Light Lights mask as targeting the tones I wanted to reveal on the adjustment layer. Instead of just creating a selection from the Light Lights mask and painting through it, however, I also subtracted off the Super Lights. I want the very lightest tones to stay nearly white, and by subtracting them from the selection that is painted through, they won’t receive much paint and will remain concealed from the adjustment and unchanged in the image.

So, after creating the Lights-series of masks on the Channels panel, here’s the process for making my desired selection:

1) Ctrl+click (Mac: Cmd+click) on the Light Lights mask thumbnail—this loads this mask as a selection.
2) Alt+Ctrl+click (Mac: Opt+Cmd+click) on the Super Lights mask thumbnail—this subtracts these tones from the selection.

I now have a selection that is targeting the tones enclosed by marching ants in the figure below–light tones are selected but very whitest tones are not.

The next step is to paint through the selection onto the black layer mask to reveal the blending-mode adjustment in the desired parts of the image. There are likely marching ants from loading the selection, and it’s helpful to turn them off by typing Ctrl+H (Mac: Cmd+H) so they don’t hamper judging the effect that painting has on the image. Even though the selection outline is hidden, the selection will still be active and directing paint to the desired tones.

Single-click on the black layer mask on the adjustment layer making sure the framing brackets are around the mask.

The “color” to paint with is easy: white. The mask is 100% black, completely concealing the blending mode adjustment. To reveal the adjustment in the image, white paint needs to be applied to the mask. So make sure the foreground color is white. Type “D” to reset the colors if white is not the foreground color.

Select the Brush tool by clicking on it on the Tools panel or by typing the letter “B”. The opacity setting for painting will depend somewhat on the mask(s) chosen or combined to make the selection to paint through. Selections made from masks with pure or nearly pure white areas in the mask pass more paint through the selection and require a lower opacity setting to reveal the adjustment. A good starting value for opacity in this case is 10 to 20 percent. Selections made by subtraction within the same series will often have the “white” pixels subtracted out of the selection, so a higher opacity setting is necessary to force paint through the “grayer” pixels that remain. Fifty percent is reasonable choice for these selections. There will always be some experimentation in mask painting, and opacity is easily reset based on what happens as paint is applied.

Now that this is all set up, it’s just a matter of clicking and dragging the mouse across the image in the areas where the adjustment (darkening in this case) needs be revealed. Releasing the mouse stops the painting. One brush stroke is usually NOT sufficient to create the desired or perfect reveal of the blending-mode adjustment. There are two alternatives. If the reveal is insufficient, additional brushstrokes can be applied. Perhaps increasing the opacity or changing the size of the brush (bracket keys) will be necessary. However, layering in multiple brushstrokes to slowly reveal the adjustment is often desirable as long as each stroke makes a slightly visible difference.

If the reveal is too pronounced after a single brushstroke, undo it using Ctrl+Z, (Mac: Cmd+Z), and then lower brush opacity, reduce brush size, or possibly load or create a new, more restrictive selection to paint through.

The goal is to sequentially add white paint to the layer mask to allow some amount of the full-on blending-mode adjustment on the adjustment layer to be revealed in the image at just the desired level in the just the areas where it’s desired and in just the tones that need it. By only passing paint through selected or partially-selected pixels, the luminosity selection automatically directs the paint to just the tones that need to be adjusted. The luminosity selection also insures that less than perfect mousing keeps paint inside the desired tonal lines.

The image below shows the painted mask and can help to better understand what’s happening with this type of luminosity painting.

The first thing that can be seen in the mask is an outline of parts of the image. Since the primary luminosity mask (Lights) is a gray-scale of the original image, all subsequent luminosity masks derived from this primary mask show image detail as well. A selection created by subtracting different luminosity masks, as was done in this case, still has partially selected pixels that mimic the luminosity in the original image. Painting through a selection based on the pixel variables in the original image (a pixel-based selection) recreates the contours of the image in all subsequent masks and when painting through these masks. It also helps insure that the painted areas blend perfectly with the rest of the image.

Luminosity painting works because not all pixels receive the same amount of paint. The desired tones that need to be adjusted by the adjustment layer’s blending mode receive more paint, and the tones that don’t need adjustment receive less or none at all. To increase the effect in certain parts of the image, apply more paint with additional brushstrokes or use a brush with a higher opacity setting. This variability in the final mask is one of the advantages of luminosity painting. Instead of being limited to the selection defined by single mask, the mask can be enhanced in any area by simply applying more white paint through the selection. The enhancement can continue until the area being painted is 100% white, a complete reveal of the adjustment layer’s adjustment. The painted mask clearly shows that differing amounts of paint were applied to different areas. Some areas are very white to reveal more of the blending-mode adjustment, some are completely black where no painting occurred at all, and some areas show various levels of gray indicating partial reveal of the layer’s adjustment.

This painted mask is actually the result of painting through two different luminosity selections, and it points out another advantage of this technique: It’s possible to paint through any number of selections to create the desired reveal of the layer’s adjustment. So it’s like using several luminosity masks on one layer mask and choosing which parts of them and to what degree they will benefit the image. In this case, most of the painting was done through the Light Lights minus Super Lights selection described above, but when repeated brushstrokes started to reveal darkening in some adjacent areas where darkening was not desired, a Bright Lights minus Super Lights selection was used to restrict the reveal of the adjustment to even lighter tones in the image.

Once you have a feel for luminosity painting, using it to create or enhance layer masks becomes a logical next step. Painting through a pixel-based selection, like a luminosity mask, applies paint in proportion to the pixel-based selection(s) in the original mask. The pixel-based quality of the mask is retained so that what is revealed or concealed by the painting blends perfectly into the rest of the image. Very precise masks are possible using this procedure. Selections from multiple pixel-based masks can be used, and they can be painted to any level between pure black and pure white to make the perfect reveal of the underlying adjustment. The effects can be subtle or significant; it all depends on where the light wants to go. I hope that you’ll try it and that your images will benefit from this technique.

A PSD file containing the complete Photoshop workflow for this image can be downloaded at the bottom of this page.