7 Helpful Green Screen Tips to Ace Your Next Shoot
From Hollywood blockbusters to news broadcasting, green screens are a powerful tool every filmmaker should know how to use. Green screens allow filmmakers to separate a subject from the background in post-production. Once the filmmakers have taken out the background, they can replace where the green screen originally was with whatever footage they wish. For your next project, apply these practical green screen tips to take your production to the next level.
What you need to create a green screen effect
● A digital camera or smartphone
● A green screen — you can find portable, industry-standard ones online for a reasonable price.
● Lights — if you do not have battery-powered LEDs or hot lights, a practical lamp or bulb will work, too.
● Editing software — for example, Adobe Premiere Pro and Final Cut X have chroma key built into their software already. You just have to search for it under the effects tab.
How green screens work
In post-production, a process called chroma key is used to eliminate the solid green background from your subject. Chroma keying is a form of composting, a post-production term for editing in layers. Once you select the solid green color you are trying to key out, you are left with a subject and a transparent background.
Now you can add in a new layer of footage that will take the place of where the green screen once was. Make sure the subject layer (what you would like to see in the foreground) is above the background layer in the sequence. When done well, a proper chroma key can add substantial production value to your content. The following are seven green screen tips for how to produce footage for a perfect key.
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 a difficult time distinguishing the darker greens from the lighter ones. Make sure when lighting your green screen, 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 just focus on lighting the subject. However, be sure to use whatever lights you have to evenly expose the green screen background.
2. 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. Having your subject wear colors that are 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.
3. Separate the subject and background
Putting distance between your subject and the green screen will eliminate the possibilities of casting harsh shadows from your subject 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. Having several feet of separation will allow you to place lights behind the subject to light your green screen background.
4. 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 appear softer in the background. Soft focus smooths out the green screen to blend it into a more uniform color.
5. 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 as double your frame rate. If you are shooting 24fps, then make your shutter speed 1/48. If there is in fact 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 when making the shutter speed too high, it will change the exposure of the image.
6. Adjust native ISO
The ISO is the sensitivity of the camera sensor. When the ISO is too high, then you will get grain on your footage that will make the chroma keying process difficult. Every digital camera has a native ISO, and it varies depending on the camera, but 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.
7. When to use a green screen vs. blue screen
Green is not the only color that editing software can key out. A blue screen is also commonly used in the industry because it has a lower luminosity, which is better suited for low-light shooting. However, there is a downside — subjects and set design are much more likely to contain the color blue than green.
Blue screens also have less of a spill around the edges of your key than a green screen. Sometimes a hairline can be difficult to key out when using green screens due to this spill. Make a judgment of what color you believe will work best for your production.
The use of a green screen is more common than one would think, and these green screen tips demonstrate how the process of using one is not too challenging. Green screens open up a whole new world of creative filmmaking from VFX to allowing talent to perform driving scenes safely in a parked car. When subjects are keyed out properly, the viewer should never suspect there was a key in the first place.