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Try a CC05M, CC10M or CC20M Kodak Wratten filter. These filters are magenta, and tend to fix orange-reds, along with greenish yellows and overly vibrant greens.


FLD filters (a salmon color) have also been used.


Of course, they lose luminence and are something of a heavy-handed solution, but many members have found this useful.


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Filters cause a loss of contrast range. With a digital PJ, you ain't got much in the first place. Fix it -properly- at the screen. See the classifieds.


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Ken Hotte

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Red and what color make Orange? That is right, Yellow. The yellowish tint from the type of bulb that the LT150 uses contributes to the orangish-hue of the reds that you see.
 

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Ken,


"Filters cause a loss of contrast range. With a digital PJ, you ain't got much in the first place."


I think with the illuminated blacks of digital, this is not the case, because filtering will lower the black level the same percentage as brights.


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Noah
 

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Discussion Starter · #7 ·
I believe Niggenz is correct, although He is addressing the problem and not the solution. The funny thing is until recently the reds were great. I am assuming that the gamma tables were set with a brand new bulb. Now the bulb has aged and turned more yellow. Does this sound correct?

I have ordered colorfacts so I will be receiving it soon. Could this problem be fixed in software? What ever became of adjusting the gamma tables?
 

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Quote:
Originally posted by SofaCinema:
The funny thing is until recently the reds were great. I am assuming that the gamma tables were set with a brand new bulb. Now the bulb has aged and turned more yellow. Does this sound correct?
I also have an LT150 wih about 60hrs on it. So further down the road with more number of hours..will I be looking at an inferior picture?? So what does the 1000 hr lamp life mean?
 

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Quote:
I think with the illuminated blacks of digital, this is not the case, because filtering will lower the black level the same percentage as brights.
I've used a magenta filter with an LCD projector I used to own, and I did find that the lower black level was a nice side effect of using the filter. However, Ken is right, adding another component into the optical path does lower the contrast. I just had to look at the projector-side of the filter while I was using it. Even though it was a coated filter, a substantial portion of the light hitting it was reflecting back into the optics, thus lowering the contrast.


Dave
 

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Dave,


"Even though it was a coated filter, a substantial portion of the light hitting it was reflecting back into the optics, thus lowering the contrast."


This can be addressed by tilting the filter so the reflected light is directed away from the optical path.


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"At this point (introducing a tilt), it had better be a quality filter."


Why is that?


"Still...it is best done at the screen."


Sorry to take a fall on this one, but I agree (to absorb some ambient light hitting the screen, right?). However, it's way easier to use a filter.


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Noah
 

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In my broken optic-lais.. having to do with distortive characteristics of cheap filters when placed at an angle. Refractive, perhaps?


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Ken Hotte

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Ken, when using dlp projectors with vip lamps (that doesn't happened with uhp lamps) to project shades of white we can see that yellowish color on the screen, do you think that we can correct that with the color of the screen?


Federico

 

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I've done exactly that for a few DLP screens. i've re-balanced the color at the screen for proper reds. The same caveat about available contrast range being affected by grey levela and screen size, also applies to the color correction as well. I need to play with DLP units to get that right as well. I can fake it, which I did with the last two screens I did, but the best is done in a totally custom fashion, on site, with the given projector in question. Granted, the differences will be minor, and, a color corrected screen (period) will do wonders for the overall color balance, even if it is not an exact match. The one DLP screen I made, I sent to Alan. That was, oh, quite along time ago. He seemed to like it. I made it ona scrap of material that was totally unsuited for such work, as I wanted to see the effects of making mistakes with the screen paint.


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Ken Hotte

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