The 7 Deadly Sins Of Chroma Keying

Sucker Punch Greenscreen BTSTo say that chroma keying is challenging is an understatement –  sometimes it’s damn near impossible. 

There are many pitfalls to look out for. But, with a little precaution you’ll be on your way to pulling clean keys in no time.

This list of 7 deadly sins will help you prepare to work with green screen and avoid costly mistakes.

1.Fix It In Post Production

This is a big one.

How many times have you heard someone say “don’t worry about it, we can fix that in post”. Attitudes like this are lazy and bad for your production.

Pre-production is the time to do tests and make sure everything is running smoothly.

Fixing problems before your production begins can save your ass and has saved mine on numerous occasions.

The bottom line: garbage in = garbage out.

2.Beware Of Wardrobe & Shiny Objects

Make sure all talent is aware of what colors they need to avoid. A green shirt or jacket worn by an uninformed actor could spell disaster for your shoot.

Jewelry and other shiny objects can also be a problem.

Dulling Spray can be used to help knock down reflections.

3.Dirty Green Screen

Dirt spots on your screen can ruin your shot. Maintain your walls with a fresh coat of paint at least once a year .

Do your best to keep the floor clean.

If the floor is not in the shot – lay cardboard over areas where people will be walking and always keep an extra can of green paint handy for touch ups.

4.Keying In Your NLE

Your NLE(non-linear editing system) is built for editing, not keying!

Many NLEs have built in keying plugins – but they don’t have the proper compositing tools to do the job right. You’ll have a much easier time keying in a program such as After Effects.

Do yourself a favor and invest in the proper tools to get the job done.

5.Poor Uneven Lighting

Keep your lighting as even as possible across your screen.

Use a waveform monitor or zebras to detect any inconsistencies in your screen lighting .

Check back soon for an in-depth tutorial on lighting for green-screen.

6.Compressing Your Footage Before Keying

Never re-compress your footage before keying.

It’s best to export to an uncompressed tiff sequence if your camera is using a highly compressed format – such as hdv or avchd.

Software such as After Effects will run faster by employing the technique.

7.Beware Of Spill

Keep at least 8 feet between your green screen and actor.

The goal is to create two pools of light – one lighting the screen and the other lighting the talent.

Spill from the green screen should not illuminate the actor.

Test this by turning off all but the green screen lights.

Next – move your actor into  position. If they are lit by green spill move them forward until they are in complete darkness.

Now – turn off the green screen lights and use the second light set-up to illuminate your actors .


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