Photoshop Trick: How to Swap a Photo Background Using Only Blend Modes
Here’a neat trick for you Photoshop lovers out there. If you’ve shot a subject in front of a gray background, you can actually swap that gray background very easily using only Blend Modes. No selection or refine edge necessary.
This post-processing walkthrough comes to us from Unmesh Dinda of the YouTube channel PIXimperfect, and it’s admittedly not the most intuitive way to drop in a background. Selecting out your subject is still going to give you the cleanest edges without worrying about spill-over from the brush. But if you’re in a hurry, this is much quicker than painstaking use of the pen tool, refine edge, etc. Plus, it’s a great lesson in blending modes.
So, how do you do it? The process is basically 3 steps long once you have your main image and your new background plate selected as layers.
Step 1: Duplicate the portrait layer twice, naming one “Hard Light” and one “Fill In,” and move both above the background layer. Your layer order should be Portrait Layer -> Background Plate Layer -> Hard Light -> Fill In.
Step 2: Turn off the Fill In layer, and change the Hard Light layer blend mode to… Hard Light.
Step 3: Turn on the Fill In layer, apply a black layer mask on top, and paint over your subject using white. If you’re careful and take your time, none of the background plate will sneak into the portrait, replacing only the background itself.
As you can see from the before and after above, the tutorial goes well beyond the application of this simple technique—he continues editing the image, adding some Color Look Up Tables (LUTs) and otherwise changing the image to make it distinct. But the basic technique is what the video is REALLY about, adding those two layers and using them to (1) drop in a new background and (2) mask out your subject.
Check out the full walkthrough for yourself up top, and let us know what you think in the comments. Is it a hopelessly limited waste of time technique that will result in a sub-par swap, or is it worth keeping in your back pocket for those times you’re in a hurry?
