How to easily make your own green screens using After Effects.

I'm going to green screen Peter Griffin from this clip as an example.

The first thing you should consider when rotoscoping any character or object from a pre-existing video is that there should be a high contrast between what you want to keep and the background you want to key out. I chose a cartoon for this tutorial because it's easier to show you the process. You can see how there are clear cut lines between Peter and the background behind him. The more contrast there is, the easier it'll be to rotoscope. Also, You want to choose characters or objects that very little to no motion blur as blurred edges tend to make rotoscoping very difficult and sometimes impossible.

This is what it'll look like when it's done.

You can see here that this is a blue screen and not green. Green screen is just a term used because usually the screen would be green and actors would wear any color clothing other than green. In reality, the background can be any color so long as that color isn't found in the object or person we'd like to keep. The reason for this is when you apply your green screen to another video and remove the background color, it'll remove everything with that color. If I had made the background here green, when I apply it and remove the green, Peter's pants would also disappear. Peter isn't wearing anything blue, so I made a blue background.

Import your video and set the Composition Settings.

Import your video to After Effects. You can see I already have it in the composition window on the left. Click "Composition" from your top menu. Set the size, frame rate, and color background you want. Here I kept the size and frame rate of the original video, and here's where I made the background blue. Don't use a frame rate less than 20 or your video will look choppy.

Start your rotoscope.

Left-click hold and drag your video file from the composition window on the left of your preview window to your timeline under your preview window. Click on the "Rotoscope" tool from your top menu. It's the icon located just to the right of the eraser tool. Double-click on your video layer in the timeline. This will open a new tab in your preview window. Your arrow cursor will now be a green circle with a plus sign in it. When you left-click hold and drag on the preview window, you'll see a green bar appear and that'll set an outline in pink to the nearest border. Everything within this pink outline will stay and everything outside the pink outline is being erased. You can't see it erased now but you'll be able to see it later when we click back to our original composition preview window. The size of your rotoscope brush can be made bigger or smaller by holding down "Control" (command on Mac) on your keyboard and left-click hold and drag left to make it smaller and right to make it bigger. Keep dragging the green bar across the character or object you want to keep until it is completely outlined with the pink line.

Tell After Effects what you want deleted.

As I stated, everything inside the pink outline will stay because you dragged the green bar over areas you want to keep. When you did this, you were telling the program what you don't want erased. Now you have to tell the program what you want to delete. This step will help when you're moving from frame-to-frame and the character starts moving. The program will be able to more easily distinguish what to automatically delete in the next frame and what to keep. To do this, hold down the "ALT" key ("Opition" on Mac) and your green icon of a plus inside a cirlcle will change to a red icon with a minus inside a circle. Left-click hold and drag red lines in the areas around your character. This lets the program know that these areas of colors are not wanted when you move to your next frame.

Moving from frame to frame

There are 2 ways to move from frame to frame, manually and automatically. Let's start with the manual as it tends to produce the best result. To move forward a frame press the "2" key on your keyboard, and to go back a frame press the "1" key on your keyboard. As you move forward a frame, you'll see the pink outline will move and readjust to stay around your character. This is why blurry edges or fast movements can throw off the rotoscope. When you move to the next frame, sometimes the pink outline will go off track. It might either go into your character which will end up erasing a part you didn't want erased, or it'll expand outwards from your character which would leave in areas of the background you wanted erased. You can just fix this by left-click hold and dragging the green icon to reinsert areas within your pink outline, and "ALT" + Left-click hold and drag and run the red icon over areas you want to delete. Continue moving forward frame-by-frame by pressing "2" making adjustments by adding and deleting whenever your pink outline goes off track. Manual rotoscoping is better and sometimes necessary if there is alot of movement or some motion blur.

Automatic rotoscope

In areas of your video where your character or object is still or the motion is very slow and smooth, you can use the automatic rotoscope. Just click the space bar on your keyboard the program will automatically move forward in frames. The pink outline will adjust by itself and this can save you time. However, if there's a lot of movement or the edges of your character are blurry, the pink outline easily and quickly goes off track, and you'd have to go back frames and re-adjust manually. Here you see that only Peter's mouth is moving, and his body is completely still. Since my pink outline is just encirling his body, this is the perfect time for me to use the automatic function. In most of my rotoscopes, I usually use of mix of automatic and manual rotoscoping.

Finishing up the rotoscope.

When you've gone through all the frames and reached the end of your clip, click on the "Composition" tab on the top left over your preview window. This will show you the clip with everything keyed out so only your background color and everything that was within the pink outline showing. You can move your timeline marker across your timeline to check and make sure it's how you want it to be. If you see any frame that has something you missed (deleted areas you wanted to keep or added background you wanted deleted) just click back on the "Layer" tab next to the "Composition" tab and re-adjust the pink outline accordingly. You can further fine-tune your green screen with the options in the project window on the left of your preview window. First, check the box that says "Refine Matte". This will make some alterations to make your green screen look better automatically. You can play with the setting as you like. As every green screen is different, there's no one particular set of settings to go by. Just play around with the settings until it looks the best you can make it. The "Smooth" setting smoothens out the edges. "Feather" will soften the edges. "Choke" will delete 1 pixel layers at a time from the edges if you decrease it and add an outline 1 pixel layer at a time as you increase it. "Reduce chatter" reduces the amount of change to the edges as the video goes from one frame to the next. "Motion Blur" is used to clean up edges when there's motion blur in the video.

Your finished green screen.

When you finally got it as good as you think it'll get, render your video. Remember you can still further improve on it when you apply your green screen to another video. To see how to do that, refer to my tutorial about using green screens. Once you apply the green screen and key out the background color, you can make more adjustments. For example, if the edges are still too rough or there's an outline you can't get rid of, you'll be able to do it then.

Use your green screen.

Finally, just find the best use for your new green screen. I used this for an example. If anyone has any questions or problems, please feel free to send me a message anytime. Happy giffing! :)