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Isolating a subject from a background so you can use it in a composite can be quite tricky.
For movies and TV shows, the most common way is to shoot everything on a green screen. As long as the subject isn't wearing anything that closely matches the green in the frame, software can be used to replace the background with whatever you want. There’s very little green in human skin so it’s excellent for isolating people. With programs like PhotoKey 7 Pro, many photographers are starting to shoot on green screens too.
In this tutorial I’ll look at how to isolate a subject from a green screen in PhotoKey and create a quirky 80s composite using an action from PhotoDune.
Shooting on a Green Screen
For this tutorial, I’m using a green screen image from PhotoDune. There are a couple of issues with this image that, if you’re capturing your own green screen photo, you should correct. That said, part of the reason we chose this image for a tutorial (beyond the vibrant couture) was precisely because these are the kinds of issues you will probably have to deal with at some point when shooting green screen, so the skills we'll cover below should come in handy if you regularly work with composites.
Green Screen Issues
First, the model is too close to the green screen. She’s casting a shadow on the background, which means it doesn’t appear as a single, uniform colour.
Second, the model and green screen aren’t separately lit. The model should be lit how you want and the green screen should be lit evenly, otherwise you get the kind of tonal variation which you see in this image.
Third, the green screen isn’t flat. To the right of the model’s head you can see ripples in the paper. Again, this creates variance in the colour of the screen.
Finally, the subject’s turquoise dress has too much green in it for anything but a perfectly lit green screen. If you’re going to use colours that contain some green, you need to make sure that your background is as uniform as possible.
Even with these issues, PhotoKey is more than capable of effectively isolating the subject from the background in our example image. If you are doing something where you need a perfect composite, you need to start with a better image. For more information on green screen photography, check out Dave Bode’s course.
1. Isolate Your Subject
PhotoKey 7 works both as a standalone app and a plugin for Photoshop. The best way to use it is as a plugin. You can also use Photoshop itself to isolate your subject, but if you intend to do this kind of work often having a dedicated tool is likely worth the investment.
Duplicate the Background and Fire Up PhotoKey
To start, open your image in Photoshop and duplicate the Background layer. Also go to Image > Mode and select 8 Bits/Channel. The PhotoKey plugin doesn’t work on locked layers or images with a greater bit depth.
Select the duplicated layer and go to Filter > Photo Key > Edit in PhotoKey 7 Pro… This will load the image into the PhotoKey plugin.
When the image loads in the plugin, PhotoKey will automatically detect any green screen and try to remove it. If you’re working from a good base image, PhotoKey will get it perfect first time. If, like me, your green screen photo has some issues, you’ll need to tweak the settings.
Adjust the Cutout
My main problem is that I’m losing foreground detail, especially in the model’s dress. To fix that, I pulled the Clip Foreground down to 43.8 and the Gamma up to 2.53. Everything else I left to PhotoKey’s best guess.
Tip: For information on what each slider does and how it will effect your composite, check out PhotoKey’s user manual. If you’re working from a good starting image, you won’t need to change a thing.
Preview the Results
To see how PhotoKey is doing, you can switch the View from Result to Matte. This will show you the black and white matte that PhotoKey is using to mask out the background.
Output Your Work
Once you have the subject isolated, click Send Back to Photoshop.
2. Create the Brush Layer
If you’re creating a regular composite, you’d now want to create a mask from PhotoKey’s output. You could then add any background you wanted to the image, match the colours and edit things how you please.
For this tutorial, however, I’m using a cool Eighties Retro Style Action from PhotoDune. To use the action, you need to create a brush layer above your subject and paint over where you want the effect to be applied. Instead of going with such a crude and inaccurate option, I’m going to use PhotoKey’s output.
Command-Click—or Control-Click if you’re using a Windows PC—on the PhotoKey output layer to select its contents, then fill it with any solid colour. I just used the default black.
Rename the layer to brush. If there are any areas where PhotoKey’s matte wasn’t perfect, you can correct them with the brush tool. I filled in a few areas of the subject’s dress that PhotoKey had missed.
With that set, it’s time to run the retro action.
3. Run the Action
Download and install the 80s action. You also need to install some custom brushes that the action relies on.
Select the brush layer and run the action. This is quite a complicated action so even on a fast computer it will take some time.
Add Images to the Canvas
At four stages you’ll have to add images to the canvas. Navigate to where they were downloaded, select the right image and click Place. The correct order is Sun, Lines, Floor and then Grunge. Once they’re placed on the canvas, position and transform them until you are happy with the result. Press Return or Enter and the action will continue.
Tip: I found it best to do a trial run of the action to see what each placed image did. I then deleted everything and ran the action again.
After a few moments the action will finish up. The result is quite intense so it’s time to tweak it until you’re happy.
4. Adjust the End Result
The 80s action creates hundreds of different layers, all of which you can modify. Looking at my result, however, the main thing I want to do is return some details to the model’s face. I also played around with the five different colour options it creates and settled on Colour Option 4.
To remove some of the stuff obscuring the model’s face, open the Elements in Front of Model group. The three sub-groups that have the most effect are Dust in Front, Dust in Front 2 and Crystallised Wire. For all three groups, I lowered the opacity and painted a soft mask over the model’s face. This brought some details back without diminishing the overall effect.
To finish off the composite, I added a text layer that said “80s PARTY!!!”, positioned it and changed it’s blend mode to Soft Light. I duplicated the layer to intensify the effect.
With that done, the crazy 80s composite was finished. Phew! Intense.
- Creating a Realistic Composite Photo with Displacement MappingBen Lucas29 Jul 2014
- Creating Flexible, Updatable Composite Images using Smart ObjectsBen Lucas08 May 2015
One of the best ways to isolate a subject from a background is to shoot them against a properly lit green screen. If you get the initial image right, software like PhotoKey can automatically remove the background. This is the technique used to make almost all Hollywood movies.
Once you’ve got the subject isolated, you can do whatever you want with it. You can introduce a new background or, like I did, use one of the many actions available on PhotoDune to have some fun.
Using PhotoKey 7 Pro is far easier than tracing around your subject with the Pen tool. Just make sure to start with a good base!