What would you capture in a clean plate before striking a setup?

[john2035]

I'm trying to understand what should be captured on set if an empty version of a shot might be needed later. This is a planning question, not a problem from a completed shoot.
Imagine a locked shot of an adult standing beside a window. There is a chance the person will need to be removed in post, but that decision hasn't been made when the setup is ready to strike.
Would you normally record an empty take immediately, with the camera and lighting untouched? Beyond matching framing, focus, exposure and white balance, what do you check before deciding that the plate is actually useful?
I'm particularly unsure about the person's contribution to the image. If they cast a shadow or appear in a reflection, is the empty take enough, or would you want additional coverage of those areas? How do you handle daylight changing between the performance and the empty take?
Finally, how do you decide how long to hold the empty frame when there are moving curtains or changing reflections? I'm not assuming a frozen frame or generated fill would replace captured background. I'd like to know which small omissions most often make a clean plate difficult to use later.

 

[David Jimerson]

That's really a decision which should have been made before you even set up.

As for a clean plate, like room tone, I'd generally suggest shooting it for the length of the scene. That goes against some conventional wisdom, but if you only have, say, 30 seconds, you only have 30 seconds.

 

[CharlesPapert]

That's really a decision which should have been made before you even set up.

As for a clean plate, like room tone, I'd generally suggest shooting it for the length of the scene. That goes against some conventional wisdom, but if you only have, say, 30 seconds, you only have 30 seconds.

I have yet to experience a situation where a plate is needed for longer than the longest shot that it would be used for in the edit. Obviously one adds a safety margin, but if one knows that no single shot would play for more than 10-15 seconds, I can't see recording 4 minutes of plate. Same goes for room tone.

If the goal is to record a back plate where a character may be added, in all instances I can recall we simply shoot the plate without consideration of the person (i.e. a shadow they may cast) because that will relate specifically to the front plate.

For scenarios where we know the back plate will be likely out of focus because of depth of field considerations, i.e the subject to be added later will be at say 5', we will shoot the plate with focus at 5' as reference, but often add an alternate plate with it sharp and maybe even a mid-focus version so that the decision on variable blur could be made later, if it gave the best results. We usually don't bother to cut between these, shooting say 15 seconds of it in focus, then giving a variety of focus versions as a series.

For backgrounds that may involve digital movement like pan and scan, we will tile the plate by delivering a methodical series of frames that for example may require 9 angles, so we start at top left, hold for the length of the plate, pan right giving a little overlap (so the right 1/4 of frame overlaps as the left 1/4 of the next frame), then one more pan to complete the top row, then repeat for the middle row of 3, and then the bottom row of 3. It's not an exact science but as long as we overlap the edges, the VFX artist can stitch these together into a complete wide shot. Conversely, we may opt to shoot a high resolution image on a still camera with wide lens that can be blown up for the pan and scan. I always consult with whoever is doing the VFX to ask their preferences and needs.