Tip: Easy fill light in Photoshop

Here's an easy technique for simulating fill light in Photoshop. If you have a photo in which the darker tones are too dark, often caused by using bounce flash without bleeding enough ambient in to the exposure, then this technique can work wonders.

Here's a photo I did yesterday. This was a test shot, flash bounced off the ceiling, and I'd forgotten to drop the shutter speed to bleed in some of the ambient, so this will work nicely as an example. Notice how some parts of the frame are very dark, ie: the man's clothes, under the chairs and under the arm of the boy on the right.

The first thing to do once the image loads in Photoshop is to create a duplicate layer. Do this either by selecting the background layer (the only layer) and pressing CTRL+J for Windows users or Apple+J on the Mac, or by dragging the background layer on to the "new layer" icon. Select the duplicate layer and change its blending mode to Screen. Your layers palette will now look like this:

And your image will look like this, way too bright:

Right-click on the Screen layer, or if you're using a Mac then do whatever you do to bring up the context menu, and select Blending Options. Double-clicking on the layer icon works too. Down at the bottom right of the panel that opens you'll see two gradient bars with sliders at either end. We're interested in the white slider for the Underlying Layer gradient, but rather than moving it, to start with we want to split it. Do this by holding down the ALT key and clicking to the left of the white slider. This will allow you to move the left side of the white slider, like this:

What these sliders do is allow you to control how much of the layer is visible, based on the brightness of pixels in the original (underlying) layer. By default, all brightness levels are visible. If we moved the entire white slider towards the middle then only the darker pixels would show through. If we moved the black slider then only the brighter pixels would show through.

For this technique we want to create a smooth blend, affecting only the darker parts of the image, so drag the left half of the white slider over to the black side of the gradient. Then move the other half of the white slider towards the middle.

While dragging the slider your image will be updated in real time so you can see how the changes are affecting it. Drag the slider as far as it needs to go, like this:

And here's the result. Much nicer!