Having a Green-Screen Thumb
With cheap editing plug-ins becoming more affordable and available, more and more productions, particularly for the web, are utilizing Green Screen FX, sometimes called Ultimatte and Chroma-key, which are actually slightly different processes. Blue-Screen Ultimatte used to be more of the industry standard, but most of the editing software now favors Green Screen.
What it is for:
All these techniques are used to allow someone to film something in the foreground and then make the background something else, from a graphic or animated background, to a photo or moving video background. If shot properly, you can even film someone against a Green Screen and then make it look like they are standing on the White House lawn or any other location you have a shot of.
Types of Backgrounds:
While many studios have a large green screen wall, there are also portable green screen curtains, cloths and there are even collapsible polyester reflector-types. You can find these products from many reputable dealers online including Digital Juice, B&H Photo and even Amazon.
What the Professional Videographer Needs To Know:
An experienced videographer will bring a green screen that is in good condition, not too faded, and without creases and rips. Wrinkles on curtain material can often be smoothed out with an iron, steamer or just by hanging; the polyester variety should not be ironed or steamed!
Some cameras work better than others for this effect. HD cameras typically work best. Avoid standard definition DV cameras if at all possible.
Camera movement should be avoided! The perspective of the background will be all out of whack with any zooming. If you are filming wide shots and close-ups of the subject, you should just edit them together. More on this later. Even pans and tilts are best avoided.
An experienced videographer will also know how to light properly for Green Screen. This will include the usual 3-point lighting, but the backlight should be a little stronger than usual to make the subject “pop” out from the background. The camera aperature should be set and locked for proper exposure on the subject prior to lighting the background. The subject should be placed far enough away from the background so that the lighting for the background does not light the subject (and vice versa). The background should then be evenly lit from both sides so that it is a bright green (or blue) color with no shadows on it. One technique for even light distribution across the background is to focus the light on each side toward the opposite end of the background so that the light doesn’t start off bright on each side and get darker toward the middle.
What the Client and Subject Need to Know:
Firstly, hire a videographer with green screen experience!
Find a filming location that is not only out of the traffic flow and relatively quiet, but is also big enough to set up a green screen (small flex-fill types are at least 9’ wide; curtains are often 25’ wide). Additionally, the room should be deep enough so that you can place the subject at least 10’ away from the background and then the camera needs another 6’ – 12’ back from there depending on how wide a shot. Filming a person’s head & shoulders doesn’t require as much space as a full body shot, obviously. The further away from the green screen the subject is, the less green screen you will have to work with. However, if the subject is too close to the background, it cannot be lit properly as mentioned earlier. If the subject moves around, he or she may go outside the green screen background from the cameras’ vantage point. Always make sure to set up a nice monitor to view the shot. Also, if you are want to show a full body shot from head to toe, the floor will also need to be either painted or draped in the same green-screen material. This will require considerable more room to work with and care will need to be taken that the material on the floor does not rip or wrinkle. Everyone but the subject should avoid stepping on it and the soles of the shoes of the subject should be clean. Flats will work much better than heels if there is any walking.
Clothing, Hair and Make-Up:
People who are going to be recorded are often told what not to wear including white or black (contrast issues), bright red (“bleeding” issues), or thin stripes or patterns (wavy “moray” effects). For Green Screen or Blue Screen, you also must avoid wearing anything with green or blue in it (many blue colors have some green in them and vice-versa). Best to wear gray, yellow, gold brown, beige, pink or muted red. This includes make-up – avoid blue mascara, for instance. It is highly likely that the videographer may apply some transluscent powder to the subject’s face (males and females) because more light than usual is used in these applications and it is easier to appear shiny. Men who are balding may particularly need powder on the tops of their heads because of the strong backlight. People with long, wispy hair, particularly blondes, may need to pull their hair together. Blonde wispy strands of hair may be extremely difficult to matte or key around.
Background Images – Perspecitve:
Before you even begin setting up for your shoot, you should have an idea of what you want to eventually edit into the background. For example, if you want the whole White House behind someone you are shooting from head to toe, then they would appear to be a good hundred feet away from it and the White House background shot would be slightly out of focus to look realistic. If you cut to a close up of the person, the background image of the White House would then show only the small portion of the building around the person – not the whole White House – and the background would need to look a little more out of focus.
Background Images – Outdoor vs. Indoor:
If the video image is an outdoor location, that would require using daylight-balanced lighting on the subject, rather than tungsten that you may use for an interior.
Background Images – Infinite White
If you simply want a bright white background that is so popular today (also called “Infinite White”), it is much simpler to just use a white seamless backdrop or paper. This will save you a lot of time in the editing room. The white still needs to be shot and lit much like the Green/Blue Screen; in fact, more light is required on the white background so that it is over-exposed evenly (without over-exposing the subject).