Find a nice picture of a car, a google image search is a good place to start.
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Grab your polygonnal lasso tool, select around the edge of one of the windows. Zoom in (control + +)to get as close as you can to the edge. Your selection should look like below..
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Once you have it selected, go to Image/Adjustments/Brightness-Contrast and lower the brightness all the way. Click ok and you can deselect.
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Repeat the steps and you'll be able to do all the windows of the car! Here's how mine looks in the end..
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I hope you've enjoyed this tutorial,