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Re: Telecine No- Drift !

Mr. Swinson comments:
> Robert implies that telecines are not stable in terms of their
> representation of transferring film image densities to video levels. 
> (deletia)
> However modern CRT based digital telecines have built in absolute
> references and drift correction. The earliest version of this was Ursa's
> automatic alignment.

This is indeed good news!  Does this mean if a client does a transfer 
at facility A he can copy the list to a floppy and take it to 
facility B which has the same models of telecine and color correction 
devices, and it will look the same?  That, to me, would be absolute.
I doubt we have that yet, perhaps in a few years...

> I can assure you
> light bulbs age a lot faster and over a much greater brightness range than
> CRTs.

Over 2000 hours on my light bulb and still zero changes.  The 
compensation circuitry certainly does its job!
> Modern telecines, both CRT & CCD based utilise digital color channels, no
> drift here.

Front ends are still analog.
> Bear in mind that CCDs are analog detectors that do drift quite
> considerably, so while the latest CCD telecines have feedback to help avoid
> the relatively large variations in their light sources, what is done second
> to second or even hour to hour to remove CCD drift ?  Maybe something or
> maybe not.

PECs are also analog devices and I've seen them become unstable at 
high gain settings (of course this was on an older machine)...  As 
far as CCD drift, it's a non-issue so I'd hazard a guess something 
was being done.

Anyway, I'm glad that telecines in general are more stable now than 
they were ten years ago.  I wonder if an absolute standard will be 
achievable or necessary.  The important thing is that in newer 
telecines, clients have a better chance of recovering their 
corrections than they do with older telecines.  As far as the battle 
goes between manufacturers and imaging devices, I'm sure there are 
strong points and weaker points in each system.  I'm glad that there 
is variety in the world, that we as facilities have options like 
these available to us.  It was not my intention to beget a war over 
which system is more stable, but to bring my own (limited) experience 
to bear to answer a question posed to the list.  Peter's reply has 
informed me of the increased stability of newer CRT machines, yet I 
think we all have a way to go before we have any absolutes in the 
transfer business! 

Robert Lovejoy 

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