Re: Luminance of movie theater projection screen

In article <C43B2DC8.2549C%graxx@xxxxxxxxxxxx>, Roger Breton <graxx@xxxxxxxxxxxx> wrote:
DougD, grADE,

Thank's for your informative replies.

So, Xenon -> 6500K white for chromatic adaptation. Interesting.

This means that only graphic arts (printing) currently uses 5000K. The old
Ektagraphic slide projectors used 3000K or thereabout.

So, television and cinema both use 6500K.

Surpisingly, most television still uses 3200k, sometimes even lower
if the fixtures are ancient. Motion picture lighting is a lot better at
being up in daylight range with the variety of Xenon and HMI, HTI
sources. I worked as a video engineer for the MN Twins/Vikings
and it used to drive me nuts trying to get a consitent white balance
as you had to fight the flood lights of the domed stadium, but they
would use 3200k up in the booths and down on the field for doing
interviews. Thank god for multiple page memory's in the camera
control units where you could store a few dozen white/black
balances per camera. I TRIED desperately to get the few techs that
handled the lighting to put on color correction to bump up to at least
5600 or better, but they just didn't get it.. The few times I was able
to color balance the interview lighting to the higher temp, field
backgrounds looked really great, and folks noticed, but it was just
too much "extra work" to get it to stick.

Obviously, our adaptation to 6500K is complete otherwise we'd be annoyed
watching a movie for 1.5 hours in the dark with bluish cats all along.

Well, it's kinda one more thing that gives film it's "look". But most of the
new digital cinema projectors that you will start seeing replace film are
all high temp sources, so that won't change and the film prints will still
be timed for daylight. Which is a good thing..
One thing to keep in mind about theater projection, is that there
are no longer any real projectionists in the booth. These days, everything
is run from platter systems that are all automated, so whoever is the
Manager for that shift is also the projectonist. So, lamps don't get
attended too as they should, and they get left in until a warning lamp
goes off somewhere. If it weren't for some smarts built into the
automation, lamps would only get changed out once they failed, and
by then the output can drop to 25% of spec. And once they get replaced,
it's no guarantee that they will get tweaked into the lamphouse which is
not physically part of the projector head, so there can be mis-alignments
between lamps that show up as hot spots, etc. on screen. Thankfully,
most of this will go away with the digital cinema!

d.

.

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