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Topic: PROJECTOR IS SHIFTING COLOR TO YELLOW (or other)
Joined: Mar 28, 2005
This FAQ will be updated as more information is gathered
This has been coming up as a frequent topic on these forums for people who are having a dramatic color shift issue with their projector. Most often, the color is shifting towards yellow and is only affecting a certain portion of the image.
Please - do NOT start a new post.
This is the topic to post into after reading the tips below and to see what other comments have come up in this topic.
1. DO NOT REPLACE THE LAMP
Lamps generate light from a single point and then direct it through the lens and optics of the projector. It is nearly impossible for a projector's lamp to cause one area of the projector to color shift. Instead, a lamp starting to go bad will appear as a general dimming of the image, a lowering of contrast, and a very mild shift of the entire image away from a natural look.
2. IF IT IS AN LCD PROJECTOR, IT IS LIKELY A BAD POLARIZER
Most often there is a color shift towards yellow that is a little bit spotty. A large 4 inch or more section will become noticably yellow, then more and more of the image will shift to yellow. It's not a definite, but the most common issue.
3. IF IT IS THE POLARIZER, WHAT IS THE REPAIR COST?
Typically, about $500 from most of what has been posted online. This amount is typically not something that people want to pay to repiar their projector as when a polarizer failure occurs, the projector is often several years old. Look at the specs on a brand new projector, it is likely less than $2,000, includes a warranty, and has better resolution/brightness/contrast.
4. WHAT IF I HAVE AN LCD PROJECTOR AND I DON'T HAVE THIS ISSUE?
Great! To keep it that way you want to make sure that you keep your air filter clean on the projector and that your projector is properly ventilated. The yellowing is often due to heat issues within the projector and the most sure fire way to cause a polarizer to fail is for heat to build up inside the projector due to poor airflow. Keep it clean!
5. IS THIS ONLY A LCD ISSUE?
It seems to be, and new LCD projectors may not have this issue going forward. The polarizers in a projector have organic compounds that break down under light and heat. This causes the failure. New LCD projectors are using inorganic compounds which are reported to be far more durable. DLP does not use polarizers. I have also not heard about this issue with LCOS (SXRD/DILA).
- Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.
Joined: Sep 22, 2006
and i would like to add in the technical details for the technically curious, partial copy and paste from my recent reply:
an lcd works by polarizing the light into horizontal and vertical wavelengths. there is a simple science experiment that can be where you can take one horizontal polarizer and shine a light through it and see horizontal lines shine through, as you would expect. then do this again but with a vertical polarizer, you see vertical lines shine through. now add these two together and what do you get? the two filtering out both the vertical and horizontal wavelengths, leaving no light. now, here is where the liquid crystal comes in, it sits between these two polarizers. the liquid crystal is bifrengent when current is passed through it (it twist) and in turn rotates the light and allows it to pass through the second polarizer. however, as it gets untwisted less and less it rotates the light less and allows the second polarizer to block the light more and more. fully untwisted it allows the light to be blocked by the second, vertical, polarizer.
now, for single lcd panel designs there are simply subpixels with different color filters. for 3 panel lcd designs there are three black and white/colorless panels where white light is shined through equally. but before the light reaches the lcd panels it passes through a different color filter for each panel, one filtering all colors out except for blue, another green and another red. after colored light passes through each panel it is then reconverged back into a single, aligned, beam and is then projected through a lense and onto the projection surface.
so, when a polarizer goes bad for a particular lcd color panel that light is not blocked when it should be. there for disrupting the process of either blocking certain colors to reproduce another color, or producing blacks. whites are least affected since white is produced by all light passing through.
there are different types of polarizers, some organic and some metallic based. previously it was felt that the metallic ones were not practical so the organic, photofilter ones were used. even so some manufacturers still did use non-organic polarizers in the past in some models, but this was a rarity.
so if you see splotches it may be an organic polarizer going bad.
some examples of the problem (taken from various bigscreenforumers when posting their problems):Picture 1Picture 2
[Edited by jarrod1937 on Apr 3, 2007 at 2:21 PM]
Joined: Aug 8, 2005
- Now I'm the one that get's to say "I mean no disrespect", but this post seems rather Anti-DLP and very Pro-LCD. I'm just saying ya know.
[Edited by Natja-ss-1334 on Jan 1, 2008 at 8:58 PM]
Experienced with Yamaha Dpx-830sl, Mitsubishi HC1500, Infocus SP7210, Optoma HD80, Optoma H78DC3, Optoma H27,Optoma H31, BenQ 6100,Infocus 4805, and many others.
Joined: Jan 23, 2008
Well probably because LCD projectors have this problem and DLP's don't?
Joined: Jan 8, 2008
Sorry for bum in here. I might not have the same yellow patch as described but the vertical green strips following all images certainly a problem in my Panasonic PTL592. Please see pic. I hope some experienced users here can shed some light for me. Thanks in advance.
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