(3) Click on RGB to open the channels, choose Blue.
(4) Since there is no yellow channel in RGB mode, reducing some blue will make the color look yellowish to simulate a tungsten light.
STEP 4. MASKING THE LIGHT.
Now we will hide the light by using a layer mask.
(1) Ctrl/Cmd+Click on the Layer mask to load the selection of the head.
(2) Click on the Curves layer mask.
Press the D key to reset Photoshop colors.
Press Cmd+Delete (Mac) / Ctrl+Backspace (Windows) to fill the selected area of the mask with black.
The curves adjustment should now be hidden by the mask.
STEP 5. ADDING THE RIM LIGHT IN PHOTOSHOP
The trick is moving the mask, so only the edge of the light is seen.
(1) Click on the Curves layer mask. Drag on the image to move the mask. For more precise control, use the arrow keys on the keyboard. TIP: (holding down Shift will move by 10 pixels each time you tap the arrow key).
The edge of the mask looks really hard and fake. Let’s fix it.
(2) Open the properties panel (double click the mask to open it). Increase the feather until the edge looks soft and the light looks natural. We now have a rim light, but there are a couple more steps to make it look more realistic.
STEP 6. ADDING A DOUBLE RIM LIGHT.
Why don’t we add another rim light to the right side of the face. It’s really easy, now that we have already done the work.
(1) Using the rectangular marquee tool, make a selection around the right half of the face.
(2) Make sure you are working on the Curves Layer mask. Choose the move tool.
(3) Drag the selection to the left and reveal the rim.
STEP 7. REFINING THE LIGHT WITH A PAINTBRUSH
Lets make the light look more realistic. TIP: Look at references of rim light photos and study them for a more realistic result.
Choose a soft edged brush and white for the foreground color. When we paint on the mask, we will be adding light. To paint on a mask, select the mask and paint over the photo.
Paint on the edge of the chin to extend the light. Also add a little more to the ears and areas that need more light.
With a black brush on the mask, we can hide areas of light.
Clean up the overspill on the chin, darken above the cheeks, around the eye sockets. Also touch up bits of the neck and shoulders.
And here is our rim light, thanks to Photoshop.. but wait, there’s more.