Adjust Tone for Easy Masking
Steve Weinrebe
Masking is challenging, especially when trying to build a selection mask on very dark or very light images. Over the years of creating a mask on, for example, a white product on a white background, I have fallen back to this technique again and again as a fast way to see what you are doing!It is unlikely you would use a jack-hammer to crack a macadamia nut. We think of powerful tools when we are doing jobs that require powerful solutions. But if you really want that macadamia nut, and the jack-hammer is sitting right there, well, why not? Now what does that have to do with Photoshop? Photoshop has many powerful tools but bottom line, they are the tools at hand no matter what you are doing. This technique is a case in point. I'm a stickler for excellent selection masks, but when working on a very light or very dark portion of an image, it is difficult to see the edge of what you are trying to mask. So I add a Curve adjustment layer and darken or lighten the image just so I can see what I am doing. Think of this technique as putting on shades if the image is too bright, or turning on the lights if the image is too dark.
Too Dark to See? Add a Curve to lighten the image (temporarily).
Let's work with my photograph of a boxer's shoe, for which I want to lighten the rear of the shoe to gain a little more separation between the shoe and the background. I need to just brighten things up enough so that I can make my selection; not destroy pixels or do anything permanent, just a quick solution using a powerful tool.
Step 1:
In the Layers palette add a Curves adjustment layer, and drag the curve upward [in RGB default "Light (0-255)" mode in the Curves display options, if you have those options open] to lighten the image. Remember this is an adjustment layer we are using simply to see, so don't be afraid to use extremes because we are going to get rid of the adjustment layer as soon as we are done with it.
Now that we can see, make and refine the selection
Step 2:
Now that the image is insanely brightened we can go ahead and make the selection along that rear, dark, edge of the shoe. In this case I used the Quick Selection tool, which did a reasonably good job of fleshing out the selection.
I might now zoom well into the image and nip and tuck the selection using the Polygonal or Freehand lasso tools (Shift to add, Option/Alt to subtract) but sometimes it is worth a trip to Refine Edge just to check if there is a quick solution to refining the mask. After clicking Refine Edge in the Options bar (visible when a selection tool is the active tool) I can choose my overlay from the bottom of the window and play with the sliders to see how far I can get refining the selection's edge.
In refine edge I clicked the "Quick Mask" view which gives me a ruby colored mask for viewing. Then I dragged the Smooth slider all the way to the right, because the selection created by the Quick Selection tool was a bit rough and jagged. When finished I click "OK" to dismiss the Refine Edge dialog box.
Turn off the visibility of the Curves adjustment layer, and edit the image within the mask's boundaries
Now that I have the selection mask I can go about my business lightening the rear of the shoe to separate it from the background. There are many ways to do this (of course) but one of the simpler and most direct is to paint "lightness" onto the image using the Dodge tool. With the selection mask in place, the effect of any paint strokes I make will be constrained within the selection.
Step 3:
Edit the image within the un-masked (selected) area using the Dodge tool to lighten along the edges. Here I use a large, round, soft brush, with "Shadows" selected in the Options bar (because I want the results of the tool to be emphasized in the shadows and darkest tones)
Note that I'm using only a 10% Exposure value. This tool is tricky and can quickly reduce contrast and create unnatural tones, so I am using it with a very "light" touch (no pun intended). I make a few strokes at this very limited 10% value to separated the rear of the shoe from the background.
Save the selection and delete the Curves layer
Step 4:
Saving selections is good policy. When we have gone to the trouble to make a refined selection as I have done here, I save it as an Alpha Channel by clicking the mask icon at the bottom of the Channels palette, and then save the image document as a PSD or TIFF file supporting layers and channels, for maximum flexibility. I can always save it as (File > Save As...) a JPEG, PDF, EPS or other file type by flattening the image later on.
Remember that Curves layer? It served it's purpose well, but we don't need it now, so I can delete it by dragging the Curves layer to the trash can icon at the bottom of the Layers palette, or simply leave the layer visibility turned off.
But what if the image is too light?
We do the opposite. Here is an image of a star torn out of paper that I used for a magazine cover image. Making a selection of the inside of the star isn't so difficult, but in this project I want to make a selection of the outside torn edges which are barely visible.
Note: In all honesty I could bring out the torn edges in lighting the photograph, which I ultimately did, but I subdued that shadow detail for the purpose of this tutorial. I have photographed a tremendous number of white product images on white backgrounds and all these steps are valid for anything similar that is too light and lacks contrast to see edges.
Step 1:
We'll follow steps similar to the project with the dark shoe edge, but this time I will add a Curves adjustment layer to darken the image so that I can see; using Curves to put sunglasses onto the image, so to speak. However this time I add two anchor points onto the curve by Command (Mac), or Control (Windows), clicking in the image; once on the tear, and once just outside the tear. Note that the points on the curve are very close together; that's expected.
By dragging the lower of the two points downward to darken that tonal value, and all the tones below it, the tones separate more between those two critical tonal values (the tear and just outside the tear) than if I simply dragged the curve downward to . That's all I want to accomplish with this curve, again just so that I can see well enough to make a selection mask along those edges.
Step 2:
Now that I can see those edges along the tear, I can make the selection mask. In this figure below I am using the Polygonal lasso to make the selection, dragging polygonal lines short distances and clicking each time I want to change direction.
Once finished with my selection I can check it, and possibly refine it, using Refine Edge. Note that I reduced the Feather to zero for sharp, defined edges. Other than that, the mask looks good and I can dismiss the Refine Edge dialog box by clicking "OK".
Step 3:
Save the selection, and delete the Curves layer because we no longer need it.
Now I can use the saved selection to create a composite image by activating the selection and inversing it (Select > Inverse), so that the area outside of the star and torn edges is selected.
Step 4:
Copy a different image into the clipboard. In this case I chose an photograph of clouds to copy into the clipboard (Select > All, Edit > Copy). Then using Paste Into (Edit > Paste Into) the image copied into the clipboard pastes into the selection as a new layer.
We have used a very powerful Photoshop tool, two really (adjustment layers and Curves), to quickly and drastically alter an image simply so that we can see what we are doing. A Levels, or Brightness/Contrast adjustment layer may work just as well. In either case we want a fast and non-destructive way to lighten or darken an image so that we can see what we are doing with the selection tools. Once finished making the selection the adjustment layer is no longer necessary to the image and can be hidden or removed. Powerful tools for fast and necessary chores. Macadamia nut anyone?
Steve Weinrebe:
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Photography © Steve Weinrebe, Getty Images
