Insert Poster - Does Chroma Keying help at all

So I’ve watched the videos on how to replace a sign in the shot with a plate. All well and good. However, this would be necessary mainly when using a run and gun production style because there’s no time to setup the prop sign.

So, what If you have the option to setup a green poster inside the poster frame and hang that on the wall instead of an actual poster. Is it easier to use continuum Complete to insert the plate using a chroma key, corner pin operation or just use the standard Mocha Pro Insert module?

If the Mocha Insert Module is easiest, is there any reason to use the green poster rather than the normal poster that would hang there on a normal day?

Well, Mocha would need a flat wall around that poster with enough detail to track instead, so using a green poster would even be contraproductive if the original poster has good detail.

A four point tracker is more critical than the planar tracker in Mocha when it comes to contrast, partial coverage or motion blur.

There are a couple of reasons to shoot with a green poster (if you can get the tracking detail you need from frame or adjacent wall).
i) If anyone or anything crosses in front of the poster, keying means you cut down on any roto work to keep the screen replacement looking realistic.
ii) You get to keep realistic shadows and reflections over the replaced poster if your camera is moving.

I had to do a ton of these a few months back and they shot with a green poster. It made life easier for simple setups or where the actor crossed in front of the poster. For more complex camera moves, it made things harder as there wasn’t always enough detail to track or a co-planar object. At that point it was a case of getting the best track possible and working it with the AdjustTrack module.

I actually did some tutorials on this topic for Master Mocha Vol. 2, which go into different strategies for exactly this topic.

Cheers,
Ben

2 Likes

Makes sense. Thanks

Hi Ben,
I bought the master mocha Vol. 2 as you suggested. I’ve been working with these techniques you demonstrated in exercise #3. Thanks for the detailed instructions. I’ve been able to use Primatte studio to key out the green and keep the reflections. However, Avid is a little different than premier in the way you layer stuff. When I have multiple plugins on the shot, they seem to create difficulties with one another. For example, On V1, I have the background footage which was shot on a Canon C100 at 28mb/s compression (and most likely, not 4:2:2 color space). Then I have to color correct the shot to match the other two cameras using the Avid color corrector. then I use BCC beauty studio to dial in the actor the way I want. Then on V2, I have a filler segment with Mocha Pro plugin applied. In MP, I roto/track the poster on the wall and setup the shape for the insert. I apply the insert clip inside the mocha pro plugin and it shows up fine in the final composition. I also use this shape as a matte on V2. When I enable the matte and adjust the feathering, the reflections show up in the final comp. This is all well and good but there are two problems. 1) The reflections change over time when I render and play the final comp 2) I need to color correct the insert clip so that it will look more natural, but when I apply BCC to V2 (the matte/insert) and set background to “filter layer”, the color work affects layer V1 as well. Any idea what I’m doing wrong here?

Thanks,
Blake

Hi Blake,

Are you asking how to not make the reflections change over time? Because the reflections should be from the original footage, isn’t it desirable that they change over time?

Can you try applying the matte for the insert, nesting the insert, and applying a color correction on that? It might fix your issue. Otherwise, @rosss might have some suggestions, he’s an Avid genius.

Cheers,
Mary

Hi Mary,
Well, it’s a static shot. The only thing moving is the actor. The reflections were pixelated and the pixels changed over time which looked really fake.

On point two, that worked even with keeping the insert applied within Mocha. Thanks!