Back to Black - Part 2
In part one I outlined a simple process for ensuring black backgrounds are always black.
But what do you do if you don’t have a solid boundary between subject and background, for example if your subject has wispy hair?
Luckily Photoshop has another ‘hidden’ or lesser known tool to help.
Advanced Blend Modes
If you have use Photoshop for any length of time you will no doubt be familiar with the common blend modes, within the Layers Pallet. Here’s an image on a black background. You can see that there is a slight spill of light onto the backdrop (exaggerated here of illustrative purposes).
Step 1 - Place a solid black layer above the image (obscuring the image underneath).
Step 2 – right click on the layer thumbnail and select Blending Options, this opens the dialogue box shown.
At the bottom there are two ‘sliders’. The top one relates to the solid black layer. The ‘underlaying layer’ is the original image... which is currently hidden.
Essentially we want to blend the top solid black where the original image was black / near black and hide the black where the underlying image was lighter.
Step 3 - Move the white slider on the Underlying Layer to the left until the subject appears. If you get a hard jagged edge, press the Alt key (on windows PC) – this will allow you to split the two smaller triangles and separate as above, creating a transition between fully blocking the image below and fully allowing it to show.
Effectively this works the same as a mask on an adjustment layer, without having to create the mask around any detail.
Step 4 – tidy up. Its sometimes difficult to see precisely where the Blend Mode has been applied. Adding another adjustment curve above, as a guide can help.
You can see that the blending has masked some of the dark areas within the subject where these were similar to the tones you wanted to hide on the background – particularly the eyelid, mouth, armpit, and shadow in the hair. This can simply be ‘fixed’ by adding a layer mask and using a black brush to paint out (mask) these areas before turning off or deleting the ‘guide’ adjustment curve.
You can of course tweak the blend layer further by changing the opacity of the layer or exploring the different blend modes from the drop down menu.