[Tig] hdcam aliasing and illegal luminance

Color dwooldridge at mac.com
Mon Mar 21 17:02:59 GMT 2011


I've seen similar issues when going to 444 sr.. 
The accidental two a links will cause the problems you are describing.
Also some I/o cards do not scale properly..

Now that being said. QT's are a pain in the butt to manage..
Gamma shifting from app to app is very common.  

Darin Wooldridge
DI Colorist _ Technical strategist
Technicolor Digital Intermediates
818-653-3918-cell
DI.Colorist at me.com



On Mar 21, 2011, at 2:14 AM, Steve Roberts wrote:

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> 
> I would imagine that the artefacts are produced because of the sample
> conversion between 1920 pixels incoming to 1440 on tape and then back
> out to 1920 again on replay - maybe a sharpening algorithm? Not seen
> this myself, but then again we tend to be pretty much SR only these days
> too.
> 
> Steve Roberts
> Senior Post Production Engineer
>> BBC Studios and Post Production 
>> 
>> 020 857 64556
>> Room B093 Television Centre, Wood Lane, London, W12 7RJ
>> 
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> 
> -----Original Message-----
> From: tig-bounces at colorist.org [mailto:tig-bounces at colorist.org] On
> Behalf Of R. Adam Berk
> Sent: 21 March 2011 08:16
> To: Telecine Internet Group
> Subject: [Tig] hdcam aliasing and illegal luminance
> 
> Sohonet http://www.sohonet.co.uk sponsors the TIG.
> Digital Vision is patron of the TIG.
> Marquise Technologies supports the TIG.
> Colorist Directory at http://tig.colorist.org/wiki/Category:Colorist
> ====
> 
> So I've just been through a weekend from troubleshooting hell.  A few
> good things did come of it, one of which is that we've without a doubt
> confirmed for ourselves that any mac application that uses quicktime for
> video i/o is completely unreliable and is under no circumstances to be
> used or trusted for mastering, but I digress.  I'll spare us all the
> immense list of details but what it all boils down to is some issues we
> had with recording an hdcam master.
> 
> Viewing a scope being fed 75% smoke bars coming from tape, it was clear
> that there was a bit aliasing.  To be expected of course.  The confusing
> part is that some of the aliased peaks fell above 100IRE, and some below
> 0IRE.  The signal coming from the smoke did not exhibit these anomalies.
> The tape was first recorded on an F500, then repeated on an SRW-5500 in
> HDCAM recording mode.  Recording the same signal to HDSR on the 5500 did
> not exhibit these anomalies.  What's worse is that the actual program
> material also threw up illegal luminance errors here and there in the
> log.  Some of these errors went as far as -9 IRE and 109 IRE.  Again,
> the same program recorded to SR throws no errors into the scope's log,
> and running a full qc report on the actual signal coming from the smoke,
> pre-vtr, reports no errors also.
> 
> Has anyone dealt with this one before?  We usually master to SR and
> rarely go to HDCAM so if this is old news, please excuse my dumb
> question.
> 
> thanks so much to the collective experience in advance
> 
> 
> 
> R. Adam Berk
> Creative Director
> office +1.415.513.5918
> mobil +1.330.310.3950
> ichat   adam at ct-sf.com
> www.CT-SF.com
> San Francisco
> 
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