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Clockit Jamming 23.98
Published : 18th August 2003
>>>The only thing I could
think of would be if the Clockit was jamming at 29.97 into a 23.98
Camera. Has anyone else seen this or has any suggestions as to how
this mistake could have been made that would cause the problem to
occur<<<
I don't use a Clockit Box
But I was asked by a producer that told me about a problem
that she had on a HD Shoot.
Post said that Timecode was being laid down but it was jumping and
skipping frames :01, :03, :05, :07, etc
Only thing I could think of would be if the Clockit was jamming
at 29.97 into a 23.98 Camera. Has anyone else seen this or has any
suggestions as to how this mistake could have been made that would
cause the problem to occur.
I suggested to Clone the Tapes with New Timecode, That is what they
will be doing to fix it.
B. Sean Fairburn SOC
Director of Photography
Castaic Ca
>The only thing I could think
of would be if the Clockit was jamming at >29.97 into a 23.98
Camera. Has anyone else seen this or has any >suggestions as
to how this mistake could have been made that would >cause the
problem to occur.
To the best of my knowledge "23.97" and "23.98"
are the same thing. That is, the actual frame rate is close to halfway
between 23.97 and 23.98, and is therefore randomly referred to in
technical literature as both "23.97" and/or "23.98"
Lew Comenetz - Video Engineer, USA.
(I forgot the exact frequency. Perhaps someone else could write
in with it? Its a big long fraction, as in: "23.975465454 etc.")
LC.
>Post said that Timecode was
being laid down but it was jumping and >skipping frames :01,
:03, :05, :07, etc
Sean,
Is it skipping every other frame consistently, or is it seemingly
random?
Lucas Wilson
--------------------
Master of Widgets
Los Angeles
Sadly, Americans and Japanese already know this stuff, but for the
rest of the world that wonders why in the hell NTSC is the way it
is...
[bizarre NTSC history lesson on]
In NTSC, the color subcarrier frequency is 3.579545... MHz. There
are 227.5 subcarrier cycles per video line. Where Fsc is the color
subcarrier, the horizontal line frequency (Fh) is 2/455 * Fsc.
2/455 * Fsc = 15,734.265... Hz
The field frequency is 2/525 * Fh = 59.94005994...
This can also be represented as 60 * (1000/1001)
Originally, NTSC B&W TV was locked to the power frequency of
60Hz. When Color TV came along, the amount of information that needed
to be added to the signal came out to be 1/1000 bigger than 60hz,
resulting in a slightly slower framerate.
Applying the same math to 24fps...
24 * (1000/1001) = 23.0976023976...
[bizarre NTSC history lesson off]
sigh. Maybe if I click my heels 3 times, everybody in the world
will use 24fps as a standard and all this NTSC nonsense will go
away...
Lucas Wilson
HD/2K Online
Los Angeles
>24 * (1000/1001) = 23.0976023976...
I think you meant 23.976... fps? (it's confusing enough without
typos!)
Tim Sassoon
Sassoon Film Design
Argh... yes, of course. thanks...
Lucas
---------
2K/4K/8K a dollar...
Los Angeles
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