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:
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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.
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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"?
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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
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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.
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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.
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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.
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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.
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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!
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