Blockies, jaggies and posterized areas after color-correction

I'm working on an ad which was shot in color, need to convert it to B&W. We (the DP and I) found a combination of filters that gave us the look we wanted: Magic Bullet Look Suite Basic Black & White, Look Suite Red Light, plus Color Corrector (for small level adjustments). It looks really great, as it provides a slightly fuzzy, dark contrast look that's way better than just cranking down the saturation (the Red Light filter functioning just as if we had put one on the camera and shot B&W).

However, I'm getting some weird splotchy/jagged/posterized business going on in a few of the shots. All of the same angle, a MCU of one of the actors with a bit of red wall behind him. The original video has a lot of grain and just a hint of these artifacts, but the B&W filter combo really makes it apparent.

I've posted a sample here, showing before-and-after of the affected shots. See what happens to the red wall behind him, and even a bit of the picture frame when he moves his head in shot #3:
video: [www.weirdsmobile.net]

Video was shot DVCProHD 720p24 (with 35mm adapter), compressed here to H.264/Vimeo preset (it's final destination) from Cram. Any thoughts on what I could try to smooth this out?

JK

_______________________________________
SCQT! Self-contained QuickTime ? pass it on!

You're seeing a combination of two effects at once. First, DVCPRO HD just doesn't have very much latitude. It's an 8-bit format, which means it can only resolve a couple hundred different levels of luminance. Normally you can get away with that, thanks mostly to the chroma noise coming out of the sensor, which kinda-sorta looks like film grain. But take away the chroma noise ? by, in this case, taking away the chroma entirely ? and woah, that's only eight bits.

The other problem is H.264 compression. H.264 works by throwing away resolution where the encoder thinks you don't need it. Basically it looks for areas without high-frequency detail and makes them lower-resolution. Once again, you can get away with it most of the time, because the H.264 algorithm is really good at guessing what's important and what's not, and hiding reduced luminance resolution behind chroma. Except there's no chroma here, so H.264 can't hide.

There's really nothing you can do to fix this, per se. Both of these effects are intrinsic properties of the two formats you used, DVCPRO HD and H.264. One was your acquisition format and the other is your delivery format, and there's no getting away from either.

But you can try to game the system. If it were me, I'd try doing a grain pass on my footage before I color-correct it. My tool of choice for that would be Shake, because I love its film-grain node, but you can get not-as-good-but-similar results in After Effects. I'm not aware of a good film-grain plugin for Final Cut, but I wouldn't be surprised if one exists.

Adding grain is a really good way to minimize visible banding. For instance, if you shoot a grainless, high-bit-depth format like Red, but have to deliver in an eight-bit format, adding grain before you output can help smooth out areas that would otherwise band on you, like a clear blue sky behind an actor. It's also pretty much mandatory whenever you work with motion graphics that include subtle luminance gradations.