Chroma Keying

02 Jan 2024

19 Jan 2024

pro tip, really watch out for your shutter speed because if its too low, getting the green screen out is gonna be a pain.

Currently at 1/50: moderately slow.

Other comment: match to frame rate of your video.

All lights at 5600K.

21 Jan 2024

  1. Set up even lighting
    Among green screen tips, this is the most important. If the green background is not a solid color, then the chroma key software will have difficulty distinguishing the darker greens from the lighter ones.

When lighting your green screen, ensure there is even, soft light on the entirety of the green screen. This is crucial for a proper key.

Many filmmakers overlook this essential part and focus on lighting the subject. However, be sure to use whatever lights you have to expose the green screen background evenly.

  1. Have your subject wear contrasting colors
    Do not wear green, as you will blend into the background, and the chroma key will make whatever green article of clothing you are wearing disappear. Have your subject wear colors on the other side of the color wheel to help avoid any potential mistakes.

Although, purposefully dressing your talent in green can produce a desired effect that is often used in the industry if you are trying to portray an amputee.

For example, in the film, Forrest Gump (1994), Lieutenant Dan’s infamous amputated legs are just green tights that they later keyed out in post-production.

  1. Separate the subject and background
    Putting distance between your subject and the green screen will eliminate the possibility of casting harsh shadows onto the green screen.

If your subject is standing right in front of the green screen background, it will be impossible to keep the screen evenly lit behind your subject. Several feet of separation will allow you to place lights behind the subject to light your green screen background.

  1. Use low aperture
    Opening up the aperture of the camera lens translates to a lower F-stop number. The lower the F-stop of your camera, the shallower the depth of field.

With several feet of separation between your subject and the green screen, if your subject is sharp in focus, then the green screen appears softer in the background. Soft focus smooths out the green screen to blend it into a more uniform color.

  1. Apply a high shutter speed
    Setting your camera to a higher shutter speed will prevent motion blur. If your subject is not moving, for example, during a news broadcast, keep your shutter speed double your frame rate. When you shoot at 24fps, make your shutter speed 1/48. If there is a lot of motion happening in front of your green screen — for example, an action sequence — make sure the shutter speed is higher, around 1/80 or 1/100.

Keep in mind that if you make the shutter speed too high, it will change the exposure of the image.

  1. Adjust native ISO
    The ISO is the sensitivity of the camera sensor. When the ISO is too high, you will get grain on your footage which will make the chroma keying process difficult.

Every digital camera has a native ISO, and it varies depending on the camera. Still, with a simple glance at the manual — or by conducting a quick Google search — you will get the answer for your particular camera. The native ISO is the best ISO for the sensor, where it does not have to up its voltage to increase exposure in low-light scenarios.