[Tig] 16fps Film Transferred on Rank Cintel & Pulldown

David Tosh dlt at earthlink.net
Fri Oct 22 16:44:05 BST 2010


Craig Leffel wrote:
> Isn't it true that the Meta-speed add on for Ranks delivered a locked transport...

> ----- Original Message -----
>...As far as I know, most, if not all telecines are not capable of a "locked" sequence when transferring any speeds other than 23.98 and 29.97 in 525 worlds, as well as 25.00 in 625 worlds.  Later URSA telecines were designed with a "locked" sequence when running at 24 fps in a 25fps video standard.  In the URSA handbook, the sequences were described for various frame rates but they were not guaranteed.  So while most of any given sequence would indeed follow the exact sequence, there would be the occasional added or missing field to make up any long term variation of the linear film speed with respect to the video output.  
> 

In my studies of Rank sequences I learned that MKIII and URSA machines 
Vari-Speed and fixed speeds were driven by a write vertical pulse 
generated from the digital scan converter's reference. A system of 
counting horizontal lines (which are always at a constant rate,) to 
result in the closest frame rate was used. This means that all speeds on 
a Vari-Speed MKIII and all URSAs (as well as all Meta Speed servos) 
result in a locked, predictable sequence of film to video fields.

The trick is in determining the start of a sequence. The longest 
sequence is a couple of dozen frames.

I'll have to dig up an old program that calculates the sequences to tell 
you what the sequence for a given selected transfer is. This is true for 
525, 625 and 656 system standards.

More after I crack open a few floppy disks containing 1980s era Turbo 
Pascal source code...

---
David Tosh
Recovering 3perf PROM reprogrammer



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