chroma-key
Chroma key
Chromakey Production is the magic process of creating images where the background or any object in your scene can be made transparent allowing you replace it with a different image. From the Invisible Man to Perfect Storm to the nightly news Weather Report, chromakey is an essential part of today’s video, cinematic, and photographic production industry.
Not only is Chromakey a powerful production tool, using the process is some of the most fun you can have with your projects.
Chromakey is achieved by shooting your scene with a solid color background or covering an object in the scene with a chromakey color then keying out that color in post production with the use of keying software or a hardware keyer.
Especially for novice producers, setting up for chromakey production can have it’s challenges. Proper lighting and having enough space to work in are the most important aspects of getting professional looking results.
The following is, “Chromakey Set-Up 101″ for “head-to-toe” full body framing. Follow these instructions to the letter and you will get superb results with most any keyer. Varying from this formula will almost always result in less than desirable keying results
Eos MAGIC 10x 20 and 12×24 Chromakey Backdrop Kit offers incredible quality and performance at an unbelievable price. You MUST have this size screen at a minimum to a get quality head-to-toe framing video. DO NOT buy a screen that is smaller than 10″ x 20′ for head-to-toe framing. They simply will not work properly for anything but waste-up head-shot or "talkin head" work.
The Basic Rule when setting up for Chromakey production to get quality results like you see on a hollywood production;
- The ideal "minimum" room size for head-to-toe full body chromakey production is 16′ wide x 18′ front to back x 9′ Tall.
- Set up your Backdrop Support System by threading the Crossbar through the Rod-Loop in the Muslin, attach the Crossbar to the Support Stands and elevate it to a height of 8′ from the floor. Ensure you are perfectly level to the floor.
- Ensure you use the 6″ Spring Clamps provided in our kits to stretch out wrinkles in the cloth by attaching them around the vertical side stands and clamping firmly to the edges of the muslin cloth. Then adjust the crossbar to pull the muslin tight between the left and right stands.
- Roll out the remainder of the screen as far as it will go.
- Ensure you create smooth “Cyc” (radius) in the cloth where it transitions from the vertical back to the floor.
- Smooth out all wrinkles. Use gaffer’s tape at the edges to secure the cloth to the floor allowing you to stretch it tightly.
- Do what is necessary to achieve a smooth wrinkle free vertical and horizontal surface.
- Place 2 Heads of equal power on the extreme right and left edge of the screen 7″ from the back vertical wall of the screen. Draw an imaginary line across the screen floor between those 2 lights.
- Your subject needs to be 8 feet in front of the back of the screen.
- You must use a lower power Overhead Hairlight of lower power than the other lights in the system positioned behind the subject illuminating the back of their head and shoulders.
- Place an overhead “Hairlight” 4 feet out from the back wall as high as you can go in your room (maximum 9 feet) and face it forward toward the back of your subject. An EZ LITE400 or DayFlo-PRO500 fixture is ideal for this light.
- Position your subject just in front of the imaginary line that goes between the 2 lights illuminating the back of the screen. Ensure your talent never crosses that line during their performance.
- The camera needs to be the same distance from the subject as the subject is from the screen.
- Position your camera 1-2 feet out from the front edge of the screen.
- Set up a Keylight 4 feet to the right or left of your camera.
- Set up a Fill light to the opposite side of your camera mirroring the Keylight.
- DO NOT USE AUTO EXPOSURE SETTINGS OF ANY KIND ON YOUR CAMERA . Manually set the exposure on your camera to make your talent look perfect.
- Refer to the main picture on this page for proper lighting configuration.
- You are ready to get started with shooting!
You must have the ability to light the back of the chromakey screen independently from your subject. To accomplish this properly you must use a minimum of 4 to 5 light heads when working indoors to do the job correctly. You’ll need 1 to 2 light heads to light the back of the screen, a Key-light, Fill-light, and overhead “Hair-light” for your subject.
Your chromakey screen must be evenly light from edge to edge with smooth soft light. Adjust the lighting until there are no cold spots at the edges. You will get substantially better result if you use highly diffused light. Fluorescent Production lighting like the DayFlo series of lighting is optimal. If using Tungsten lighting ensure they are equipped with softbox diffusers.
If you don’t use separate lights for the screen and place the subject too close to the chormakey backdrop the Key and Fill lights will cast shadows from your subject onto the screen making it virtually impossible to get a clean key on a moving subject because your keyer will see those shadows as a different color green/blue in the area of the shadow directly around your subject than the rest of the screen.
The biggest mistakes producers make when setting up for chromakey work is trying to use too small a screen and not using 5 light heads as described above.
Being that the camera ends up at a minimum of 16 feet from the chormakey screen, you’ll need as wide a background area as possible to ensure your framing is filled edge to edge with the background to key properly.
The next most important thing to consider with a complete Chromakey Kit is it’s ability to stretch the Muslin material tight to eliminate wrinkles that get into the material when folded up and stored.
Now widely copied, our Chromakey Kits feature a Telescoping Crossbar and we supply you with 8-10 Heavy Duty Screen Clamps which allow you to effortlessly adjust the distance between the stands to exactly the width of the Muslin Screen and create tension across it’s width. This feature instantly smoothes out wrinkles in the cloth thus eliminating the potential for shadows which create dark lines on the screen which can make keying difficult..
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