[tig] Spirit and C-PD

Digital Praxis digital.praxis
Tue Jul 1 19:33:00 BST 2003

While on the subject of image data, I recently had to find a different way to set Spirit for C-PD log output as we were not able to use Thomson's technique as we couldn't monitor the testpoints they suggest. I was at The Film Unit in New Zealand and must say that their technical engineer, Ian Bidgood, was a key part of this discovery. I'm mentioning this as the technique seems to provide better/easier setup than the Thomson method.

In general, we used TAF to setup the system by using an normal output waveform monitor (HD but I guess SD would work too) to set black to a representative level of 95 samples and mid grey (18%) to 470 samples while the Spirit was in normal video mode (cant remember what the actual voltage reedings on ther waveform monitor but it's not rocket science to work out and as 18% grey is 50% illumination it's kinda obvious).

Obviously the whites were very clipped but this is corrected when the Spirit is set to the data/C-PD output LUT.

All setup was done via the Spirit local panel as Pandora/da Vinci tries too hard to control all aspects of the grade and you need to make sure TV Gamma is OFF and all secondry setup are bypassed. Don't inadvertantly swap control over the the grading panel (as I did once) as this changes all the local panel setups.

With TV Gamma off and secondry's bypassed uses lift and gain to set blacks and 18% grey as described. This takes a while as the two interact, as all colourist know.

When set the TAF can be replaced with the real film to be data transferred. Looking at the frame bar the blacks can be 'tweeked' to re-balence as there will be some variation, but this should be a small change...

I'm interested in comments from people doing data transfers via Spirit and the Phantom to see if this method of setup makes sense. Worked for me!

Oh, the Spirit also sets the LOG flag in the data put to LINEAR so be aware when grading later with a system that understands LOG vs LINEAR data (like iQ) as this changes the grade methodology. I hope Thomson will fix this soon.


Steve Shaw
Digital Praxis
+44 (0)7765 400 908:m
digital.praxis at virgin.net

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