How ISO, Exposure, and Shutter should be used on a Green Screen.
There are a lot of factors that go into shooting and compositing a great looking green screen. The lighting, the spacing, the camera settings, the compression, and even the lens will all effect the quality of the green screen footage you shoot. Going through most tutorials online, I found none that are thorough about the importance of camera settings to your green screen shoot.
The three main settings I want to focus on in this blog post are the three exposure settings on all cameras, so lighting is still very crucial. The three settings are ISO/Gain, Exposure/F-Stop, and Shutter speed/angle. The ultimate goal for a properly lit green screen shoot is to composite your foreground footage on another background scene. You always want to make sure that your foreground matches your background as much as possible in order to create a believable scene. Using all three of the exposure settings on your camera correctly will help you.
ISO – Keep you ISO or Gain as low as possible to avoid adding grain to your footage.
Grain, or noise, on your footage will always make it harder to key out your background. The more film grain there is in an image the harder it is for your camera to read colors, especially the color green. Really high ISO adds red, green, and blue color grain. That will make it very difficult to key out a green screen when you have green noise bouncing around on your image.
There are other camera settings that cause grain on your video like upping the detail levels and master ped. You should get to know your camera very well and avoid all those settings that add noise to your shot and use the lowest native ISO for your camera. These settings sometimes add more noise than the ISO.
If the final background you will be using has a lot of noise, then I suggest you add noise to your foreground in post-production in order to cleanly key out the green screen. This will help you match your keyed foreground footage with your final background in order to match both sources and create a more realistic scene.
Shutter speed – Use a higher shutter speed to avoid motion blur.
Motion blur in green screen video can be problematic. When your subject is moving in the frame it will have motion blur and blend in with the green screen in the background. If your subject blurs in with your green screen, it will be much tougher to key out the green screen in post-production. This will cause the part of the subject that is blurred to key out with the green screen and look horrible and amateur.
A higher shutter speed like 1/125 – 1/250 is pretty good for most hand motions and small movement from actors. Higher shutter speeds will make the actors fingers or their hair looking crisp. This will help you key out the green between the fingers or the hair. Just remember that shutter speed will effect your other exposure settings and that you will have to adjust your iris or your lighting for a properly exposed scene.
Exposure / F-Stop / Depth of Field – Depth of field will effect the way your foreground matches with your background in your final scene.
The most important thing to remember about all green screen footage is that you want the foreground image that you are capturing on a green screen to look very similar to the final background you will be using in your final scene. You really want to match both the foreground and the background as much as possible for a more professional looking final scene. There are a lot of ways to achieve this but the depth of field is the most important and the most noticeable.
If your background has a shallow depth of field, you want to shoot an image with a shallow depth of field / lower f-stop. If you have an image with a lot of depth of field, you don’t want your actor to have shallow depth of field. This will cause a lot of problems with blending the foreground and background together in a scene and will make your scene look goofy and unrealistic.
Your audience will probably not notice the difference in depth of field like a professional cinematographer would, but they will notice something is wrong with the scene. If your audience thinks there is something wrong with your scene, they will not pay attention to your video and will be trying to figure out what is wrong the whole time.
Based on how much depth of field you want to allow on your green screen footage in order to match it to your background, you should always try to use a higher F-Stop and more depth of field. This will help you in post-production when you key out the green screen. The more depth of field you have in your green screen shot, the more in focus your image will be which will make it easier to key out the green screen in post-production. If the outside edge of your foreground is soft, the more it will blend in with the green from the green screen and it will be harder to key out without keying the edges off.
There are a lot of great editing software and plug-ins out right now that make a horrible looking green screen key out really well. My favorites are The Foundry’s Keylight plug-in for Adobe After Effects and Red Giant’s Primatte Keyer. Like everything though, shooting it right will save you a lot of time and headaches in post-production. The three major exposure setting on your camera play a huge role in how well your green screen will key.
These are just three things out of many to remember when shooting on a green screen. The lighting, spacing, and tripod are just as important as the camera to the overall outcome of your green screen. I hope this has been great information for anyone looking to start shooting on green screens. If you have any questions, feel free to write it in the comments below or contact us.