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Re: URSA Color Drift

On Sep 11, 12:57pm, Dave Corbitt wrote:
> Subject: URSA Color Drift
>                       Subject:                              Time:  12:43 PM
>   OFFICE MEMO         URSA Color Drift                      Date:  9/11/96
> In searching the TIG archives I was unable to find URSA color drift as an old
> topic, only MK3 color drift.  Maybe it's in there somewhere.  Anyway, here's
> the situation.  We have 2 URSA's upgraded to 444 and both at one time or
> another have exhibited slight changes in color balance or level relative to
> auto align or standards change.  This is most noticeable if we correct and
> down to tape in one standard and then change over to the other standard and
> lay down again with the same color list.  The black levels and overall color
> balance will be noticeably different (looking at parade scope so let's not
> into possible set up problems with encoders, proc amps, etc.).  The colorist
> is typically  auto aligning at the start of the session and then re-aligning
> after switching standards.  If we switch standards and DON'T realign then the
> color levels are close but not exact.   We have clients who want rock steady
> archival color correct lists that they can return to in 3-4 months but so far
> it seems that even a few hours causes enough drift that the auto align
> come up the same way twice.  Measuring the light output of the CRT doesn't
> point to a change there.  The operators try to put an opaque card in the gate
> whenever the machine is open gate/no film to minimise PEC drift but that may
> be be a problem still.  Any feedback?
> Dave Corbitt
	Hi, there is certainly a drift when you change standards, but if you
auto align it will not improve the problem since the picture is never the same
after auto alignement even when you don't change standards, I am always careful
with pec clipping, tube/pec temperature etc, I realized by seeing this problem
on other machines in Paris, that the Ursa is not stable and I have to live with

	Jean-Clement Soret