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Carbon arc and xenon lamps


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#1 L K Keerthi Basu

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Posted 12 January 2007 - 10:33 AM

I have a doubt about what is the color temperature of the Carbon arc Projectors and the Xenon lamp film projectors. Is it necessary to grade the print for different projectors like carbon and Xenon lamp film projectos. Please explain me in bit detailed.
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#2 David Mullen ASC

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Posted 12 January 2007 - 11:50 AM

They should be similar (daylight-balanced, like around 5500K) but Xenons are slightly bluer I think. But since carbon arc projection is extremely rare these days, most people color-time for Xenon lamp projection.

It's a bit of an issue when projecting old Technicolor dye transfer prints with modern Xenon lamps since the print looks slightly cooler than it used to, since it was timed for carbon arc projection.
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#3 John Pytlak RIP

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Posted 12 January 2007 - 05:27 PM

I have a doubt about what is the color temperature of the Carbon arc Projectors and the Xenon lamp film projectors. Is it necessary to grade the print for different projectors like carbon and Xenon lamp film projectos. Please explain me in bit detailed.
L.K.Keerthibasuj


The color temperature of xenon and carbon arc are similar (near 5400K), and most differences are due to the dichroic heat filters used in the lamphouse. Today, xenon lamphouses tend to be a bit higher in color temperature (near 6000K average) and a bit on the green side of the black body locus. In practice, the slight differences do NOT usually require a change in the print balance.

Many still favor the color quality of carbon arc, as it tends to have a spectrum that is a bit smoother and less "spikey" than xenon, but the vast majority of modern theatres use xenon lamps.
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#4 L K Keerthi Basu

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Posted 13 January 2007 - 11:05 AM

The color temperature of xenon and carbon arc are similar (near 5400K), and most differences are due to the dichroic heat filters used in the lamphouse. Today, xenon lamphouses tend to be a bit higher in color temperature (near 6000K average) and a bit on the green side of the black body locus. In practice, the slight differences do NOT usually require a change in the print balance.

Many still favor the color quality of carbon arc, as it tends to have a spectrum that is a bit smoother and less "spikey" than xenon, but the vast majority of modern theatres use xenon lamps.



Thank you john, what is the standard color temperature for the projection, is the bluer xenon is ok for the projection under the standard conditions. Why you didnt mentioned about this in your practical projection points, for the better image on the screen.

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#5 David Mullen ASC

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Posted 13 January 2007 - 11:18 AM

Plus the lab is likely to use Xenon projection for its print viewing and timing decisions.
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#6 L K Keerthi Basu

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Posted 13 January 2007 - 11:42 AM

Plus the lab is likely to use Xenon projection for its print viewing and timing decisions.

Thank you David.

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#7 Dan Goulder

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Posted 13 January 2007 - 11:47 AM

Having run a carbon arc Simplex projector at a drive-in, I can tell you that the arc required continuous monitoring and adjustment, since the distance between the electrodes would widen as the carbon burned off. This would affect not only the intensity of the arc, but also gave the appearance of varying color temperature as well. The move to Xenon has enabled a single projectionist to supervise a whole multiplex. Xenon does subjectively appear to have a higher color temperature, although I don't have the actual data to back that up.
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#8 David Mullen ASC

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Posted 13 January 2007 - 01:18 PM

What's interesting regarding the issue of "white point" in digital cinema is that we now have the potential to digitally correct for any color temp variations in Xenon projection so that every viewing of a movie has the same color temp for white.

However, since a projector bulb is the only source of light for a screening, the truth is that we accept it as "white" (our eyes compensate somewhat) even if it's not the exact same color temp as the Xenon bulb in another theater. If our eyes couldn't compensate, then a 16mm screening with a tungsten lamp would look horribly orange.

I mean, we still need standards of course of screen color temp and brightness, but some variations are always going to happen. Even if I make every color print in a book match every other book, I can't know what sort of lighting people will read that book under.
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