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No Drift




WHOOOOPs.  I did not intend to indicate that  everything in telecines was
one hundred percent non drift. If that's how the message came across I
apologise.

In response to S Harman, S Russell,  R Lovejoy  and others I would like to
clarify my view on the subject.

I was not claiming that Ursa or Gold had ultimate in stability only that it
had an auto align that helped stability.

My main response on stability was considering today's latest telecines,
Ursa Diamond and Spirit.

I agree CRT brightness decays with age, so do incandescent lamps as used in
traditional CCD telecines, 
xenon lamps like CRTs  also decay in brightness with age, typically
reducing in light output to 60% over 1000 hours according to Cermax 300
watt lamp figures. 

I perfectly agree with Steve Russell that Xenon lamps do not change color
over time. 

CRT's themselves show little color change with age, we find that the auto
align differences that Steve Harman refers to are largely PEC based. 

In the instances of today's telecines the likes of Twigi and Diamond Glow,
as Steve Harman points out, fully compensate for these CRT changes of
brightness in run and stop modes and as Steve Russell points out Spirit
uses precision correction to hold the Xenon at a constant brightness. In
this respect I hope we can agree that the light sources of both
technologies are held stable, CRT by Twigi/Diamond Glow compensation and
Spirit by lamp supply feedback.. 

The only other source of potential drift in today's telecines is the
detectors and as Robert Lovejoy points out the "front end". My original
posting referred to Diamond Set which actively stabilises the PEC detectors
and front end. This should also help address Steve Harman's comments about 
PECs needing "tweaking" if the job is re-presented to the telecine.

I agree I was a bit contentious asking what means Philips took to stabilise
their detectors, the CCDs, and even re reading Steve Russell's posting I
see no reference to how this is done.  We know PECs drift and from our
experience of CCD scanners, ADS 1 & 2 and Klone,  so do  CCD black levels, 
in asking the question I thought I might be giving  Steve Russell the
opportunity to equally explain to our mutual users how today's CCDs are
stabilised. This is not a snipe I just  think we all want reassurance that
drift is a diminishing issue in telecine transfers.

I was surprised that Steve Russell regarded my whole posting as "a snipe at
our (Philips) technology", in my original posting I acknowledged that the
Spirit had lamp stabilising feedback and appreciate Steve Russell putting
figures to it's accuracy, I also asked the question about CCD
stabilisation, but the rest of the posting was an attempt to answer Robert
Lovejoy's observations about telecine drift.  Of course I biased it towards
Cintel, what else would you expect. 

Finally OK, OK maybe the term absolute stability was overdoing it a bit,
how about very significant improvements in stability on ALL  today's
telecines.

I shall now batten down the hatches, go into a deep dive and wait for the
depth charges.!

Peter Swinson.

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