Greenscreen spill correction

There are many ways to remove the green spill, so let's start simple and work our way up. A good technique is to see what an adjustment layer will do. Add a Hue/Saturation adjustment layer above the photo. Clip it down so the photo is acting as a clipping mask. You can do this by OPT (Mac)/ALT (PC) + clicking between the two layers, or just click the clipping button at the bottom of the Adjustments panel. We need to try and affect just the green areas, not the whole photo. To do this, try a little-used option on this panel. Click the Master drop-down and choose Greens instead. Now slide the Saturation slider all the way to -100. If the Master option had been left on, the photo would be greyscale, but since Greens are chosen, they are the only colors affected. The green hasn't been removed completely, but the spill's intensity has been reduced somewhat and any overall green cast to the photo has been lessened.

It's a bit better, but it's not there yet. The next step is to try and directly adjust the color of the green spill. Add a new layer above the adjustment layer and fill it with an average color sample from the photo that will counteract the green. In this case, I chose a reddish-brown taken from the hair. Change the layer's Blend mode to either Hue or Color and clip it down with the rest of the layers. I chose Hue for this example, but they are really quite similar. Currently, the Opacity is 100% and it is tinting the entire layer. The next step is to restrict this effect to just the edges and then adjust the Opacity as needed.

To do this, we need another mask. Load a selection from the alpha channel originally created by Calculations by CMD (Mac)/CTRL (PC) + clicking on its thumbnail. With the selection active, add a mask to the Hue or Color layer. Now, do a Levels adjustment, sliding the white slider almost all the way to the left. This will expand out the white portions of the mask so that this brown tint extends farther into the photo.

The next step is to expand out the mask so that more of the green spill is covered. There are a number of ways this could be done, but let's try some of the newer tools in Photoshop. With the mask active, click the Mask Edge... button on the Masks panel. Take the Shift Edge slider up to +100% and then increase the Feather amount until the green disappears. Make sure Output To: is set to Layer Mask and click OK. Now the masking is pretty much complete.

You still may need to fine-tune the edge, but it might be a good idea to pop in a new background first. That way, you'll more accurately see what adjustments need to be made. The foreground will also probably need some adjustments like Color Balance and Curves or Levels to match the background. Once you have added these adjustment layers and clipped them down to the masked photo layer, you can see what needs to be done to the mask edge, if anything. Some options to consider: lowering the Opacity of the Hue/Color layer, expanding the sliders in the green area on the Hue/Saturation adjustment layer, or doing another Levels adjustment on the original mask, as you see here. If any haloing or fringing still appears around the edges, moving the midtone slider to the right will darken up those greys and hide more of the image. Use restraint here, because you don't want to lose too much hair detail. You could also try Shift Edge in the Refine Mask options; it does about the same thing.

Now zoom out and admire your work Check to see if the shadows of the background match the shadows of the subject. You may need to mirror one or the other as I've done here. For really good photo compositing, the images need to match in terms of noise, grain, and blur. These can easily be added in with filters, especially if you convert the photos to Smart Objects.

That's it! This is the process for extracting greenscreens. You could even automate the process of combining channels and making the initial mask. Other tutorials out there use Extract (which isn't even automatically installed with Photoshop anymore) or modifying a selection with Refine Edge, but these tools really aren't designed for greenscreens. They are more appropriate for other backgrounds. This is really the way to do it and mastering these skills will open up many doors of Photoshop goodness.