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blinkstar
Joined: 29 Dec 2010
Posts: 11
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| Posted: Wed Jun 15, 2011 12:40 am Post subject: Lowering Black Level=Red Faces--Any Idea Why? Please Help! |
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When I try to improve black level by dropping my projector's brightness setting, faces, particularly faces in shadow, become very reddish in hue. To avoid this I have to bump up the brightness setting, but then the whole picture gets washed out and blacks are a light gray.
I'm running HDMI out from a WD HD Player to an old LCD projector (PLV-Z3) with many hours on the bulb. I've calibrated using the Dummies guide and my grayscale is far from perfect, but I'm not sure it is a grayscale problem ...
Any thoughts as to why lowering black level would make faces red, and/or how to fix this? It's kind of driving me crazy ...
Thanks for any and all input!
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Wed Jun 15, 2011 5:26 pm Post subject: |
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Grayscale problem was my first thought. If brightly-lit faces look good, but dim faces look red, that tends to indicate your low-end grayscale is off. Can you post your calibration curves?
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blinkstar
Joined: 29 Dec 2010
Posts: 11
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| Posted: Wed Jun 15, 2011 9:34 pm Post subject: |
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| garyfritz wrote: | | Grayscale problem was my first thought. If brightly-lit faces look good, but dim faces look red, that tends to indicate your low-end grayscale is off. Can you post your calibration curves? |
Hey, thanks for responding!
I don't have a recent set of calibration curves but I will make some. I think you are right about low-end grayscale--it is difficult for me to set with the EyeOne meter because anything below say 40 IRE is bouncing all over the place. My bulb is pretty dim so it just can't get a good reading on the lower end of the scale is my theory. I'll try to get a defusor and see if I can take a reading directly from the lens. Thanks again for your input!
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed Jun 15, 2011 9:51 pm Post subject: |
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Couldn't that be the problem right there, the bulb is off? (not off as in turned off you wits), but off color balance, which makes it way off 6500K?
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blinkstar
Joined: 29 Dec 2010
Posts: 11
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| Posted: Thu Jun 16, 2011 6:02 am Post subject: |
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| Curt Palme wrote: | | Couldn't that be the problem right there, the bulb is off? (not off as in turned off you wits), but off color balance, which makes it way off 6500K? |
Thanks for weighing in, Curt!
I've seen LCD bulbs go bad before, but isn't it still possible adjust/compensate for that? If the bulb is off, shouldn't the meter still be able to read it correctly and tell me what I need to add or subtract? I know there must be issues with this bulb. For instance, I have both a 20 CC R and a 20 CC B filter attached to my lens, because without them, red and blue are just way too low, no matter how high I crank up the cuts and gains ...
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Thu Jun 16, 2011 7:56 pm Post subject: |
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Yes, the chromatic properties of the bulb can change as it ages. Might be more than your CMS can compensate for. I wouldn't think that would affect low IREs differently than high, though, because the bulb is constant. It's the LCD panel that affects the brightness. If the grayscale is on for high IREs, then the bulb must be reasonably OK.
If your eyeOne can't read below 40IRE, yeah, try pointing the sensor at the projector. It's not ideal but it should give you an idea if the bulb itself is off.
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blinkstar
Joined: 29 Dec 2010
Posts: 11
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| Posted: Thu Jun 16, 2011 11:22 pm Post subject: |
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| garyfritz wrote: | Yes, the chromatic properties of the bulb can change as it ages. Might be more than your CMS can compensate for. I wouldn't think that would affect low IREs differently than high, though, because the bulb is constant. It's the LCD panel that affects the brightness. If the grayscale is on for high IREs, then the bulb must be reasonably OK.
If your eyeOne can't read below 40IRE, yeah, try pointing the sensor at the projector. It's not ideal but it should give you an idea if the bulb itself is off. |
Thanks for responding, gary! I put the diffuser on and adjusted HCFR accordingly. I put the EyeOne a few inches from the lens and started taking measurements. No fluctuations in low IRE readings so I went ahead and started setting them. Switched back and forth between my old settings (taken from the screen) and the new taken from the lens, and was surprised to discover I couldn't see much difference between them, at least not with my naked eye. My impression was that blacks are now more accurate however ...
But ... the problem with reddish faces or darker areas remains. If I drop black levels (or gamma) then everything starts taking on a reddish hue. If I lower black a LOT then the whole screen darkens and turns red ... so I still haven't managed to solve my problem, I'm afraid.
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