Green Screen using AVC-Intra 100 ugly

Question

Been using the hpx300 for approx two months mostly in 720p with great results. Just wraped our first true HD green screen shoot using avc-intra 100 at 24p with the intent of producing a white background mac-ad type, 5 min talking head corporate piece in SD. I had the camera mounted at 90 degrees to capture the 1920 pixels of subjects head-to-toe so I could then manipulate individual zoom and placement in post within a SD timeline. I've got two issues: one is that the images in post seem noisy, and any movement, as in subjects walking across screen, is a total mess - I say seem because all recording and playback on location looked just fine on a 1920x1200 monitor via blackmagic i/o box. I normally do basic editing in premiere with much help from AE for composting and color correction etc. Keylight has always worked great in the past. I must have something wrong with settings in the avc-intra HD content? Secondly, workflow is a bit convoluted... Keylight doesn’t apply in premiere, and AE doesnt do avc-intra. The workaround is to export avc-intra premiere timeline to AE and key that.  In theory it should work just fine, but again my images are just noisy. Could this PR to AE workflow degrade image quality?  Any suggestion greatly appreciated! Thanks, Matt

Answer 1

Poster must be busy shooting more stuff....
Found some info on that " hollywood camera " site.....
IS HD REALLY HD- GREENSCREEN ISSUES
These plates were all shot with an HVX-200, mostly with the 100 MBps DVCPROHD codec. This was good enough for us for Visual Effects For Directors because we had specific needs, but we don't consider them good enough for full film production.
Here's why:
COLOR SAMPLING: We      prefer all green screen to be 4:4:4, so every pixel has a unique color.      4:2:2 only updates the color every second pixel, but green screen      desperately depends on a sharp, accurate, scientific color transition.      With 4:2:2, you're operating in half resolution. But if you downsize, like      we downsized to 720x480, you're at full resolution again. So because we're      delivering in SD, the plates are 4:4:4 for us. They'll just be 4:2:2 for      you if you're delivering for an HD movie.
PIXEL ASPECT: When      a camera is listed as 1920x1080 HD, that's really stretching the truth.      You'll see that all our plates are in 1280x1080, which is the original      camera resolution, meaning that the plate has to be stretched 150% on the      X-axis to be in the right aspect. In other words, you're only operating at      66% resolution on the X-axis. Did someone say "smearing"?
NOT EVEN 4:2:2: By      the time 1280 has been stretched to 1920 to make up for the 1.5:1 pixel      aspect ratio, 4:2:2 has been stretched out too, basically becoming      4:1.5:1.5
LENS RESOLUTION: Nobody      besides DPs really thinks about the fact that a lens has a resolution.      Zoom lenses are made of many lens elements in a clever configuration, and      each element introduces some blur. That's why top-notch DPs like to use      prime-lenses cut from diamonds from King Solomon's mines, because if the      lens limits the resolution, it doesn't really matter how well you record      the signal after that. Some people have come to the conclusion that the      HVX-200 is really a 720p camera, because the 1080p resolution doesn't      really come through. We tend to agree, but we don't want to start a      religious war, and will say that it's just our personal experience. On top      of that, we've used a $500 wide-angle adapter on some shots, which really      butchers the pixel resolution, so even though we're recording at 1080p,      we're really not. But 1080p allowed us to record with the 100 MBps      DVCPROHD codec, which meant that we still got a very respectable resized      SD signal out of it.
BAYER PATTERN: Most      cameras use a Bayer pattern on the chip, so that every pixel is EITHER      Red, Green, or Blue — but not at the same time. A full Red-Green-Blue      pixel is derived mathematically by interpolation. It's no wonder that some      organisations are starting to call for an objective standard for what      really constitutes a pixel, because a Bayer pixel is definitely not a real      pixel — more like half a pixel. By the way, there are twice as many Green      pixels than Red or Blue in a Bayer sensor, so you're far better off using      green screen than blue screen on video.
HALO: Even      with the internal sharpness generator completely disabled, the HVX-200 has      a clear black fringe several pixels wide on the right side of actors on      green screen. Panasonic vehemently denies it, but it's very easy to see.      In this      picture, notice that white areas get a fringe, but darker areas, like      her legs or hair, don't. Panasonic's explanation has been that it's just a      shadow from the lighting (huh?), but the halo is on the KEY side — so the      only plausible explanation is a quantum singularity localized to the actor      which bends light as it passes by her body. We think it comes from the      Bayer pattern, but we're not sure. And Panasonic shouldn't feel bad. A Nikon      D80 does it too.
HEAVY COMPRESSION: Even      though it seems like a lot that we're recording at 100 MBps in the      DVCPROHD codec, if you calculate the bit-rate per true output-pixel, we're      actually still compressing at a whopping 15:1.
NOISE: Video      cameras in this price range tend to have rather high noise, and on top of      that, they're usually 8 bits per color channel. This can result in some      highly visible shadow noise that almost pixellates when the brightness is      just on the edge of a bit-threshold. You can see some of our plates doing      this.
An HVX-200 and all its brothers and sisters in its price range simply don't have the horsepower for full pixel, high dynamic range, high resolution, uncompressed production that you need to do truly professional green screen. Green screen is ultimately a scientific process, and is one of the most demanding things you can do with your camera. Regular live-action images are MUCH easier for your camera to handle, so for regular filmmaking, your camera is fine, don't feel bad.
We have nothing against the HVX-200 or its brothers or sisters — come on, we shot a whole DVD set about visual effects on it — but it's important to really understand what the limitations are. It's fine to own your own camera for regular filming. For green screen, you should consider renting the very best you can afford — and make every decision right, which is where we come in.
Thanks for reading!
Rod