April 04, 2018

Green screen, lighting, and Mr. Miyagi

by: Adam Loehr
Editor

Green screens are everywhere, it seems. Where they once were only used in expensive productions, or to add dynamic visuals to the weather report on the daily news, now even basement-studio YouTubers are implementing green screen technology to present composite images – like the weatherman standing in front of a giant map -- together into one seamless presentation. It’s a powerful tool, but it’s also one that’s really easy to get wrong. Let’s take a cue from Mr. Miyagi in the first Karate Kid movie, as he teaches his student the mindfulness that leads to success. With patience and a methodical approach to lighting and shadows, you can get the green screen results you want when everyone is watching.

“Paint the fence” evenly with correct lighting

Green screen is also known as chroma key compositing, or just “chroma keying” – it refers to the differentiation between specific colors in the frame: Chroma = intensity of color, and key = importance. The reason green is most often chosen is because it is most unlike human skin tone. If you’re shooting outside with lots of existing greenery, a blue screen would be the right choice. In either case, a properly lit green screen is crucial.


 
Denver Bronco Von Miller on our ReadySet Cyc filming for Bleacher Report and Old Spice.

Just as Miyagi doesn’t want his fence splotchy and uneven, we want our green screen to be nicely lit and even. If you have a light meter handy, your goal should be for the green to reach a luminance of 70 I.R.E. across the board. The even green will help the visual effects team out in post-production immensely.

Viewers likely won’t directly associate how they’re feeling about your commercial with bad lighting, but if it looks lousy, those negative feelings can easily carry over into the consumer’s perception of your brand. Lighting is how you paint your fence, so do the work to ensure an even coat.

“Sand the floor” and eliminate green spill

The next common pitfall of most green screen shoots is ‘green spill’ and casting shadows. Casting shadows speaks for itself, but green spill is a glowing halo that completely surrounds the talent’s outer edge, like a chalk outline.

  • Green spill is the result of the green screen reflecting onto the subject’s skin or clothing, which can leave the edges of your talent fuzzy or less sharp in the post-production process.
  • Casting shadows has the opposite effect, where the nice flat green screen that you just lit has a similar fuzzy particle effect where the shadow is changing the intensity of the green, and therefore not being removed with the rest of the Chroma key.  

 
Actor Scott Takeda makes a new acquaintance during a Brock Creative production.

Instead of physically ‘sanding the floor’ we’ll tweak this saying slightly to ‘span the floor.’ Each shooting environment is different, but try to keep 15-20 feet between the green screen and your talent. Use your best judgement based on the shoot. You don’t want them so far away that the green screen isn’t filling the background, but just as a light bulb shows more on your skin when you’re closer to it, so will the green screen. This practice will minimize how much the green screen is reflecting on your talent as well as the shadows they cast on that ‘nicely painted fence.’

“Wax on, wax off” with lighting gels

Light the green screen and subject separately. The key here (pun intended) is to make sure that the source lighting, both on your set and in the final product, are identical. The final Miyagi-ism, “wax on, wax off,” relative to our green screen analogy, simply means “gel on, gel off.” A lighting gel can aid in matching color temperature all the way from fluorescent bulbs (tungsten) and the Sun (daylight). Again, your actual lighting schematic is shoot-specific. If the ultimate goal is to green screen your talent to be at the center of Madison Square Garden, your setup will be different than if the Sahara Desert was your background. Spend the extra time to light the talent individually from the green screen – it’s really going to elevate your production, and ultimately your product as well. The more time you spend in pre-production with your cinematographer and gaffer, the better the final deliverable will look.


 
The hosts of Xfinity Latino record a standup promoting the upcoming FIFA World Cup.

If your plan is to make the next Jurassic World movie with the green screen in your basement, well . . . we need to talk. There are a lot of variables to account for, so for a first-rate result it’s always advantageous to shoot in an actual studio with a proper lighting setup. An entire master class can be (and is) taught on the art of using a green screen. Some of the most effective visual effects are those that an audience has no awareness of (biggest visual effects Oscar snub = Castaway, look it up). Mr. Miyagi says to his apprentice Daniel, “first learn stand, then learn fly.” Relative to your green screen techniques, the moral to the story is simply that a professional result comes first from learning to perfect the basics.