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Magenta Cast -Tungsten Fluorecents


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#1 Miguel Bunster

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Posted 27 October 2005 - 03:22 PM

Hi,
I am using a LCD projector for a scene where a character is watching a movie. With LCD us I understand I dont have flicker problems but another DP who shot with it had another issue. The light bounced back from the screen made a magenta cast. Any one knows why this happens and how can I avoid it please?

My second question is about tungsten fluorecents. I was planing to rig some office areas with fluorecents (practical roof lights) and I have the option of going day light or tungsten. If I go tungsten I have to gel the windows (85+ND) to make them match but I gain 2/3 of a stop (shotting 5218) but it was explained to me that the tungsten fluorecents have a pink cast. It is easier to go day light and just ND windows but still looking at whats better. Any opinions on this matters would be of great help.

Thanks!
Miguel
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#2 Laurent Andrieux

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Posted 28 October 2005 - 06:27 AM

1- You can meter the color temp of your LCD projector and correct it with +/- green (some gel in front of the lens should be possible to fit, even if you have to do something so it's not close and burn..?). Otherwise, if you can't correct the projector, make your other sources have the same cast, and correct in post/timing

2- Same thing : color time the fluos and correct them...
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#3 James Mann

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Posted 01 November 2005 - 12:23 PM

if a color temp meter is not in your arsenal...

chances are that your LCD projector has a bulb in it that is somewhere close to 5600k (daylight). The magenta cast may have come from an older bulb. To be safe, find out what buld is inside and get a new one. Or put up a daylight source (kinos?) and attempt to judge the difference from your projector bulb and your daylight bulbs. This will clue you in to any strange color shifts.

as far as the tungsten kino tubes go, sometimes the 2900k bulbs appear slightly "pink" or magenta. I haven't seen it too much with the 3200k. But it is not out of the question, particularly if they are aging. You can always get a few extras from the rental house and change out which ever ones appear problematic. again, use your eyes.

But it sounds like your best bet would be to use daylight tubes, unless of course you want to feel/see a difference between the light outside and the light inside. That's sort of up to you and the director. But I wouldn't shy away from the tungsten b/c it might give you strange color spikes. Just be careful when using an incandescent (fresnel or open face) this is where you will see a difference between "kino tungsten" and tungsten. Again, use your eye. Or color temp meter.

Or if you are really concearned, use a stock that is slightly more forgiving to changes in color temp. Fuji Reala 500D is great at mixed light as is Kodak's 5205 (250D). There may be others, ask around...
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#4 Laurent Andrieux

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Posted 01 November 2005 - 12:57 PM

chances are that your LCD projector has a bulb in it that is somewhere close to 5600k (daylight)


It should be over than that but you certainly can set that in its menu...
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#5 Miguel Bunster

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Posted 02 November 2005 - 02:18 AM

HI, Thanks for all the info! I made a test on 5218 with a LCD projector and color temp. I putted the projector with a white image and measured the temp. It was about 4500K and then I shot the test with some images. It turn out well, little cold but for what I am doing it works fine.
I will try to post and image any time soon.
Best
Miguel
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#6 Laurent Andrieux

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Posted 02 November 2005 - 06:12 AM

Did you meter the cc/green/magenta as well ?
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