[Tig] Measuring a DCI-theatre projector - new vs old lamp

Gareth Havard thebighopper at gmail.com
Fri Mar 1 20:06:19 GMT 2013


Hi Ken, Carl, Richard, Graham et al!

This is something that I'm dealing daily (and can weigh in on the Spirit
too!!!)

As Ken said, the stated life of the Spirit lamps is down to performance of
calibration by FPN, to match the FPN from X number of years ago...

when a colourist throws up a previously scanned neg, after a fresh FPN and
recalls TK mems / SCC values onto the same model of machine (not necessary
the exact machine) the picture should be the same! Although this is also
down to the service conditions of the machines etc... Unfortunately I've
dealt too many times with customers running happily for thousands of hours
on a classic, only to find a lot more work when re-scanning years down the
line! It's a hard job trying to justify to customers why they should change
lamps while they're still burning... years worth of experience is why I'm
changing them religiously in my new facility + regular servicing.

On the DCI side, I'm finding in Cape Town the digital theatres are all
different. I'm using Truelight colour management for our DI grading suite
and taking tests to the local cinema via Doremi's FCP plugin...

I've mostly found environmental changes with projection windows letting in
ambient light and low level floor lighting pushing the blacks up. As Juan
stated, we also get a good picture if our lamp is at 13.5Ft-L or 17 Ft-L ,
the contrast is greater but no overexposure is seen!
I've asked to meet with the calibration company who does our local screens
and will be taking our Filmlight probe to see exactly what's going on...

I can't even imagine the drama after the Red Carpet viewing... I'll be
taking Carl's opening email to the manager of our local as I'm sure he
thinks I'm being a little anal!

Regards

Gareth Havard
Engineering Manager @ Collective Dream Studios, Cape Town
(and former DFT/ThomsonGV engineer)



On Fri, Mar 1, 2013 at 1:06 PM, Ken Robinson <flight4 at gmail.com> wrote:

> Sohonet www.sohonet.co.uk sponsors the TIG.
> Support from Digital Vision www.digitalvision.tv
> =====
>
> Hi Carl,
>
> I cant really comment on DCP projectors, but I can regarding Spirit. The
> whole point of that machine and its feedback loop was that if you changed
> the lamp within the correct time, colour temp never changed.... Well at
> least for me! The only time I had a problem was when I turned up somewhere
> as a freelance, didnt check the lamp hours, started grading wondering why I
> couldnt see through the film very well.... Some hours into the grade I
> decided to have a look at the lamp hours... 4000+, so changed the lamp, and
> everything came back! The exposure was so different that I dont remember if
> temp changed or not.
>
> Ken
>
>
> Ken Robinson
>
>
> On 1 March 2013 05:49, Carl Skaff <carl at stopp.se> wrote:
>
> > Sohonet www.sohonet.co.uk sponsors the TIG.
> > Support from Digital Vision www.digitalvision.tv
> > =====
> >
> > I just know from working on a spirit classic.... If the lamp died in the
> > middle of a grade it wasn't fun. A brand new lamp vs an almost dead lamp
> > had a very different temperature. Although that could usually easily be
> > adjusted with the sprit primaries.
> >
> >
> >
> >
> > /Carl
> >
> >
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> http://tig.colorist.org/wiki3
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