Pro Tips, Tutorials

Why You Should Always Capture Clean Plates for Post-Production

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You can do a lot of great things with your video once you get it to post, and if you’ve gotten a few clean plates, you’re going to be able to do even more. You can split screen your frame, add basic or complex VFX, and even fix visual errors, all just by shooting some clean plates for every scene. The great thing is that it’s easy to do — but, as with anything, it has its nuances. Here are the best ways to maximize your clean-plate acquisition, along with some common use cases and techniques.
 

What a Clean Plate Is and Why You Need It

A clean plate is an “empty” piece of video (or a still image) of your scene that has the exact same composition, lighting, and movement as your “final” clip. It’s the background of your scene, basically, just (usually) without your subject or other objects in it. This can be anything from a locked-down tripod shot to a dolly or aerial shot — even handheld if you’re good. VFX are actually added to shots all the time that utilize the original plates without us even knowing.

Drive Plate, Forested Hilly Rural, Light Traffic, Mostly Sunny, #8 by Stockshooter

It’s always good practice to get 10-15 seconds of your background plate for each scene or interview (or whatever you’re shooting), because it gives you a baseline for how everything can and should end up looking. If you’re shooting an interview on a day where clouds are coming and going, you can keep the lighting consistent with a clean plate and a mask/matte/crop. If you’re doing a split screen where an actor plays multiple parts on screen at the same time, you can keep them separated with a clean plate. If you’re doing any flying or super speed or explosions, you can use a plate to keep your subject separate from the background and give you more freedom.
 

How to Capture and Use Clean Plates

It can be quite easy, surprisingly. You record the scene, shot, or interview without the subject(s) in it and make sure that it’s the exact lighting and composition you want it to be. Get the footage or still from every angle and/or camera you plan on using so that you’ve got it all covered. You usually want to shoot this on a tripod to keep it easy on yourself in post, but it is possible to make a handheld or moving shot be the plate (remember you can always add “handheld” movement in post). You just need to be as close as possible (if not exact) with your movement, and you need to be good with After Effects or other compositing software. Film Riot did this with a programmed camera move and multiple takes:

 
There are basic ways to use plates, like cropping out an unwanted reflection or fading out your subject — think Yoda in Return of the Jedi (semi-spoiler? He is 800 years old for Force’s sake, though) — but you can also use it for more advanced techniques like the example above, or inserting a CG subject in frame, or even throwing an object miles away. As long as your background plate is solid and consistent, you can do almost anything. This popular video from RocketJump uses plates to get the knife tosses to seem real:

 
Check out the BTS to see how they use a tripod to make plates that are exactly the same for each trick:

 
This technique is also employed here in this short sketch from Jimmy Fallon’s Tonight Show:

They have a plate with just the actor moving through the frame and no car, then a plate with just the car driving through, hitting a dummy, then they crop, mask, matte, and make it look seamless. So, you know, if you’re into making people look like they’re violently run over by speeding cars, then (clean-ish) plates can get you there.
 

Matching the “Real” Footage to the Plate

Some of the key things you need to remember about using a background plate — whether it’s your actual scene or a background you’re adding to a green/blue screen — are the lighting, focal length, focal depth, and inclination/angle of your camera’s perspective.

For the lighting:

Keep the time of day or the light source’s position in your plate consistent by adding a glow, flare, or actually lighting your subject to match it evenly. Watch the section in this video when they put a green screen behind the subject (1:12); they put a touch of sun right on his head where the sun would be:

 
For the focal length:

Normally you don’t have to worry about this if you’re just shooting empty plates of your scene before or after your subject is there, but this needs to be followed more closely if you’re inserting the plate later. Your composition needs to look realistic within your plates; if you’re shooting at a wider focal length, it would be weird to have an extremely close up background plate. The perspective would look… off.

For the focal depth:

If you’re shooting with a wide open aperture, your depth of field will be very shallow. The same goes if you’re wide open. This needs to be reflected in your plate. You can add blurring very easily, so don’t hesitate to keep the depth of field larger to avoid any irreversible mistakes.

Close Up on Focus Pull on Film Set by Video_StockOrg
 
For the camera angle/perspective:

Again, if you’re shooting clean plates of your scene before/after your “live” shooting from the same spot, this isn’t as big of a deal, but you will have a way easier time making your project look seamless by keeping everything at the same angle and perspective. If your camera is positioned at ground level, having a birds-eye background plate doesn’t really make any sense. Mark your tripod legs, take photos of your rigs, and do everything you can to ensure you’ll repeat everything consistently.
 

Rotoscoping and Motion Tracking for Additional Effects

We talked a bit about the easier ways to manipulate the clean plates with basic cropping, masking, and mattes, but another one of the important reasons to use clean plates is that you can easily replace background elements with more complex tools like rotoscoping and motion tracking. If your sky is blown out, you can replace it. If you want to change signs, logos, or any background text, you can just put a new text box over it with these tools.

You can track that sign or logo through the whole clip and use that data to apply to your new sign or logo. You can rotoscope out an ugly garbage can or other object in the plate and then have a totally usable background exactly the way you want it.

If you’re using the 3D camera tracker specifically, you can place almost anything on a plate as long as you have it tracked correctly. This opens up so many possibilities for adding extra objects or characters into your frame to fill it in; it’s pretty much ubiquitous in movies today, as trees, people, and animals are all added to frames to make them seem more “full.” RocketJump captures this in their video about VFX really well:

 
If all else fails, you can take a still frame from your shot and create your own clean plate with the clone tool, then use that. However, it’s always much easier to just get clean footage beforehand, however.

Experiment with getting some clean plates on your next shoot and see what you can accomplish!

Do you have questions or comments about the techniques covered in this post? Tell us below!

Top image: Still from Autumn Scene with Empty Road by CaptureLight