[Tig] Measuring a DCI-theatre projector - new vs old lamp
richard at filmlight.ltd.uk
Fri Mar 1 15:09:13 GMT 2013
> From: Carl Skaff<carl at stopp.se>
> Got a question. Has anyone out there done any measurements on a theatre
> projector with a new vs old lamp?
I have been around when it happens a few times.
New arc lamps can be a bit bluer for the first few hours. I don't know
why that is, but if it is like tungsten-halogen lamps, there is an
equilibrium between the hot bit and the material deposited on the glass
envelope that takes a while to establish.
More significant is the alignment of the lamphouse. You may have to
twiddle several screws to get the lamp into the right place in a
projector to get a uniform screen temperature and brightness. As you
twiddle, you can be imaging different parts of the lamp, so the colour
temperature goes up and down. If there is nothing to twiddle in your
digital projector, this may not mean it is in the perfect position.
As the electrodes wear (it is an arc lamp, right?) the arc can change
position. I think arc lamps are retired because they flicker rather than
the colour drifts, but I bet there are plenty of people on the TIG who
will put me straight if this isn't right.
> They said they just did a full calibration... But that was just BEFORE they
> changed lamps!!!
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