Here is the final result to add focus with light in Photoshop:
Step 1 - Select your subject.
Step 2 - Create a group layer and turn the selection into a mask
Step 3 - Add a Hue/Saturation Adjustment layer, click the "colorize" button, and put "20" hue, and "20" saturation, and don't change the lightness.
Step 4 - Add a Curves Adjustment layer, and make the bottom left point (white point) "50" instead of "0", add a point at "80" and make it go to "90".
And here is the final result:
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