Masking Hair, Fur, and Other Wispy Things in Photoshop

Hair, fur, fuzz, and other objects with complex or loosely defined edges can prove difficult to select with the run-of-the-mill selection techniques. But that’s where masking can save the day. Because a mask allows for a 256-level selection, it does a great job in picking up those illusive strands of hair and such that would otherwise probably be cut off in the selecting process. Perhaps you’ve seen those photos where everyone in a composite image appears to have helmet hair? Here are the steps to avoid the Aqua Net look and select even the smallest wisp of hair:
1. Choose File-->Open.
Select an image that contains something hairy, furry, or fuzzy. A portrait is an ideal choice (unless it’s a portrait of Telly Savalas). For your first attempt at this technique, it is best to start with an image that has a pretty simple and uncluttered background. In my example, I used an image of a pensive, young urban professional.
2. Choose View-->Channels. View each channel by clicking the channel name.
Each channel is an independent grayscale image. Each of the channels in the document is a potential starting point for a mask. It is best to start with the channel that contains the most contrast between what you want to select and what you don’t. If it’s a toss-up, go with the channel that will make selecting the difficult part of the image easiest (in my example, that’s the hair). In my example, I’m using the Blue channel.
3. Choose the Duplicate channel from the Channels palette pop-up menu. Name the channel mask and click OK.
You’ve created an alpha channel for the mask. Now you can edit the mask without harming the original channel.
4. Choose Image-->Adjustments-->Levels and boost the contrast in the image by adjusting the Input sliders for Shadows, Midtones, and Highlights.
5. Select the person and his or her hair.
You can do that one of two ways:
- By selecting the person.
- By selecting the background first and then inverting the selection. In a mask, traditionally white represents a selected area, black represents an unselected area, and gray represents a partially selected area.
6. Adjust the Levels settings by dragging your shadows, midtones and highlights sliders so that the element you want to select is either all white or all black with a little gray in the wispy areas. In other words, you want to change most of the pixels in the image to either black or white.
In my example, because my guy is darker than the background, I adjusted the contrast to make the subject as black as I could while making the background lighter.
7. If you think the edges of your image need to be accentuated, you can apply a High Pass filter (Filter-->Other-->High Pass) before you apply the Level adjustment.
High Pass turns your overall image gray while leaving the edges white. Don’t use too low a radius value (start with a setting between 8 and 10) or completing the mask will be too time-consuming.
8. Refine the mask by selecting the Eraser tool and choosing Block Mode from the Options bar.
The Block Eraser is a great tool for cleaning up masks. It allows you to paint inside the mask without creating any feathered edges.
9. Press D for default colors.
Remember the Eraser tool paints with the background color, so be sure you have the color you want before you drag. Press X to switch the foreground and background colors.
10. Clean up your mask by painting with black and white.
Make sure to use short strokes so you can undo any mistakes you make.
11. Use the Zoom tool if you need to touch up the details.
The Block Eraser tool has only one size, so you have to zoom in to paint thinner strokes and zoom out to erase a larger area. Remember to leave some gray around the wispy areas; otherwise, they may look chopped off. Take your time and be as accurate as you can. This is where patience makes a big difference. If you’re not sure what you need to paint on the mask and you want to refer to the color image, simply click the composite channel (either RGB or CMYK depending on your image) at the top of the Channels palette. Then click the mask channel again to return to your mask. Or better yet, you can view both the mask and the composite simultaneously. Your mask appears as a red overlay. Your mask is refined and ready to go.
12. Click the first icon on the left at the bottom of the Channels palette to load the mask as a selection (or Ctrl+click [Ô+click on the Mac] the channel mask).
A selection marquee appears around your mask. If you want to soften the edge a little, you can choose Select-->Feather and enter a value somewhere between .5 pixel (for a low-resolution image) to 2 pixels (for a high-resolution image). Feathering allows for a softer, naturallooking transition between your masked element and the background. I used a 1-pixel feather for my image.
13. Return to the composite image by clicking the RGB channel (or CMYK if warranted).
14. If you need to invert your selection, choose Select-->Inverse.
In my example, I just filled my background with a solid color, so I left the background selected.
15. Choose Window-->Color and mix a color of your choice. Choose Edit-->Fill, choose Foreground Color for your Contents, and click OK.
Photoshop now replaces the background with a solid color. Check the edges to see how clean your mask is.
16. Make any final edits you need to make.
My guy looked like he spent too much time at the local tanning booth, so I toned down the redness in his skin by using the Variation commands.
17. When you’re happy with your channel mask, save and close the file.
It takes practice to get masking down to a science, but believe me, it’s worth your time. Nine times out of ten, a channel mask lends a much better selection than any of the easier, quicker selection tools and techniques. Instead of filling the background with a color, you can also open a second image and, with the Move tool, drag and drop your masked element into the second image. A couple of things to keep in mind when compositing with two images: First try to use two images whose lighting isn’t so dissimilar that it looks artificial. Take into account the time of day, the angle of the light, and so on. Secondly, try to select two images whose levels of focus make sense. If you need to soften one of the images, apply the Gaussian Blur filter. If your mask is good, your person should look right at home in his or her new digs.