Super Black
Thanks for the detailed description from one who does it. I will save your
excellent description for my references.
One thing I might caution you is when you read certain terms in 3DS such as
"video post" "Super black" "keying" "rotoscoping" etc. don't always assume
these terms have traditional video definitions. They are similar terms but
have been redefined by Yost group to more accurately describe the video world
as seen by the 3DS animator rather than an experienced video editor. This
doesn't make the definition wrong. It just adds new definitions to an existing
vocabularity. Thus, alpha in the 3DS arena is all about transparency, by
definition. Actually about transparency in layers of graphics files to be more
accurate. As a side bar: I once attended a lecture by Lon McQuillon. He was
asked a question about "Super Black" in a talk about the Ultamatte blue and
chroma keying. His [funny] answer was "Super Black??, I'll have to try a
bucket of that. Do you spray it on, brush or roll it?" <G>
>>><<The only way I know of to generate a value of black below 7.5 IRE is to
adjust it in a procamp with the pedestal or black level set-up before feeding
the alpha to the key input on your switcher.>>
>>That's work only if you're feeding a pure alpha signal, which doesn't need it
since it is made up of pure blacks and whites, and shades of gray to give
transparency. If you drop the pedestal on a color image you''ll pull the video
level down as well. Pulling the video level up again will change the contrast,
and the look of what one hopes is a carefully made image, besides, dropping the
pedestal will not create a difference between lowest black and the next lowest
level in the image.
I only meant that the output from 3DS will be at black 7.5 IRE. Super Balck
does not lower this when the _ALPHA_ channel is viewed from the frame buffer.
However, you can of course lower the blacks in this alpha file with the
procamp. This would in no way affect the color image blacks which would remain
at 7.5 IRE. Since I've never actually done alpha channel keying they way you
describe I'm not sure this lowering of the pedastle will have relevance. I
only originally mentioned it because I thought you were confusing 3DS
definition of what "super black" does and what you thought it should do.
With respect to your problem, I take it you use the VTR control function from
3DS??
I agree that this makes the recording of the alpha split rather difficult.
This is probably a wish list item. I don't see any way to record the color
portion of the alpha rendering to a VTR to save disk space while splitting the
alpha off to disk and recording later. I never used the alpha split when I
used the VTR function with 3DS for my diaquest board so I never ran into it.
Without going to a double rendering you would have to render to the disk both
files and then lay them to tape individually. FWIW: I spent two years
rendering and single framing from 3DS and found it was in my best interests to
render to disk, then record the frames to tape from disk. It prevented unusual
wear and tear on my VCR and tape. Also if something went wrong such as a
corrupted frame of a stretch in the tape I could just go back and re-record.
The lengthy rendering process was complete and the files safely on disk. Once
I had a confirmed tape I erased the rendered files freeing up disk space for
the next job. Even with this I still had trouble recording more than 1000
frames at a time due to tape stretch, wear and tear. I used a 7750 and a 5850
and the 5850 was far superior. Today I use a PAR and output to all formats and
do 30 times the quantity of work to tape.