Masking Semi-Transparent Fabric

Here is another image of Laurel. I want to mask out the white seamless studio background so I can composite her into another scene. The tricky part will be to mask the background showing through the fabric at the bottom, middle part of her dress:

Topaz ReMask 5 has the proper tool to accomplish this task. Start by creating a "trimap" where you paint a blue line over the edges where you want ReMask to compute the edges of the mask, and fill the areas to be masked out with red. Notice that I have done nothing to the area of semi-transparent fabric in her dress:

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After I pressed the Compute button, ReMask created a nice mask. To mask the area of transparent fabric, we need to see it better. I choose a split screen view, and changed the version on the right to "Keep" and set the background color to red to better show any unwanted white background:

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Select the Transparency Brush. It used to be called the Dual Color Selection Tool because you choose two colors: what to keep and what to mask out. You are presented with a green eyedropper. What you do is on the right version of the image you click on a solid black area of the dress, in this case the fabric over her leg. This represents the color in the transparent area you want to keep. The eyedropper changes to red. Click on an area of solid white background. I clicked on the area of white seamless just under her dress, between the legs. This represents the color you want masked from the transparent area. The red eyedropper changes to a brush. Paint on the area of transparent fabric. You will now see a little black showing through on the left (Mask) version, and a little red showing through on the right (Keep) version:

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Back in Photoshop, Option (Alt)-click on the layer mast to see it in black and white. Paint over the hard edges (with no hair) of the mask with a white brush set to Overlay. Stay away from the transparent fabric:

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Here is a closeup of the area of transparent fabric created by ReMask:

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It is masked, but the mask is somewhat weak. Set the foreground color to black, and with the brush still set to Overlay, brush over the area of transparent fabric to get this:

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Brush over the same area again:

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Brush over the area a third time:

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Now that the transparent area of the mask is stronger, we should be able to actually see through the fabric a little. Here is the final image, using a scene from Singapore's Little India district: