Optoma HD20 Possible Image Retention/Burn In - AVS Forum
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post #1 of 9 Old 08-21-2010, 07:57 AM - Thread Starter
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Hi,

I've read here for years, but never posted. Many of you have given me a lot of good advice, thank you for that. Now I have something to ask finally directly.

I purchased the Optoma HD20 last Jan. It has about 1,500 hours on the bulb. I've been noticing, well, all my family has, that during dark scenes there is a strong ghost\\burn in of the last scene left on the screen. This ghost causes weird smudging effects on some shows.

When my DirecTV goes to screen saver mode, then the logo that moves around does a drawing effect on the dark blank screen due to this image retention\\burn in effect.

I figured a DLP projector would not do this, has anyone else had an experience like this, is it perhaps because my bulb is getting higher in hours? It is really annoying and I hope it is not a permanent thing?

Thanks for any help?
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post #2 of 9 Old 08-21-2010, 08:20 AM
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Have you tried that receiver on a different television?

Maybe it is the dtv box.
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post #3 of 9 Old 08-21-2010, 08:23 AM
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DLP cannot have burn-in. Its impossible. Its just millions of mirrors reflecting light through your color wheel and each of them are either on or off at any given time.

Have you tried using a different source hooked into the projector to see if the problem isn't isolated with the current source that you are using now?

Swap those sources and see if the problem still occurs.
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post #4 of 9 Old 08-21-2010, 08:46 AM
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And the lamp cannot cause that, either.
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post #5 of 9 Old 08-21-2010, 08:48 AM - Thread Starter
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I have not tried another source hooked to the projector. I will do that. On the box, we have the DirecTV's whole home system and the other TV's do not seem to have any image retention like what I am seeing on the projector. But, I will switch some things around and experiment more.

Thanks for your responses.
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post #6 of 9 Old 08-21-2010, 10:53 AM
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Maybe a stretch but..what if the mirrors are opening/closing fast enough?
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post #7 of 9 Old 08-21-2010, 11:42 AM
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Quote:
Originally Posted by loudtoyz View Post

Maybe a stretch but..what if the mirrors are opening/closing fast enough?

Possible, but not probable. If this were the case, any change in mirror on/off speed (which is 16 microseconds) would also affect the color uniformity as each affected mirror would not be able to stay in sync with the color wheel when it was commanded to.

For some reason, the new mirrors are displaying the new image while the old mirrors are still receiving a command to display the old image shortly. It really sounds like his tuner-output on the DirectTV box.

The only thing I can think of that would cause this on the HD20 would be the fact that DLP chip boards have some kind of buffer system that supplies image data to the DLP chip through on-board memory. If for some reason that buffer has left over information in it, it may be projected onto the screen and create the effect he is seeing.

That's a long-shot though.
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post #8 of 9 Old 09-15-2010, 04:45 AM - Thread Starter
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I'm resurrecting this thread as I have an update in regards to ghosting/image retention on DirecTV with the Optoma HD20.

I never did see the ghosting occur on our other LCD TV.

The ghosting still occurs on the HD20. The other day I was watching a fairly dark movie and the ghost/afterburn was terrible. When people's heads would move, there would be many outlines of their heads or body left behind as they moved across the screen.

Just for fun I started trying different settings on the projector. I went through movie, then bright setting, both the same problem. Then I clicked the "photo" setting and poof, my ghosting was gone??

How is that for weird? I would assume then that it is something with the projector and not DirecTV at this point. Since I use movie and bright only, now since I am using photo mode if eventually it to will start to have the problem or if it is a permanent fix - sort of anyway?
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post #9 of 9 Old 03-25-2012, 07:57 AM
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Quote:
Originally Posted by lostsole1976 View Post

I'm resurrecting this thread as I have an update in regards to ghosting/image retention on DirecTV with the Optoma HD20.

I never did see the ghosting occur on our other LCD TV.

The ghosting still occurs on the HD20. The other day I was watching a fairly dark movie and the ghost/afterburn was terrible. When people's heads would move, there would be many outlines of their heads or body left behind as they moved across the screen.

Just for fun I started trying different settings on the projector. I went through movie, then bright setting, both the same problem. Then I clicked the "photo" setting and poof, my ghosting was gone??

How is that for weird? I would assume then that it is something with the projector and not DirecTV at this point. Since I use movie and bright only, now since I am using photo mode if eventually it to will start to have the problem or if it is a permanent fix - sort of anyway?

I know this is an old thread, but the last info given doesn't sound accurate to me so I want to post extra thoughts on the subject for archive sake. If I (or anyone) run across another thread to link here, I will return. Likely not though.

This sounds like the rainbow affect to me. Not ghosting. This is normal when a scene is mainly dark with high contrast that moves left and right. Of course that is based on the description only.

Also, burn in would not have any moving artifacts. Not to mention what has already been discussed, that DLP can't have burn in, which is an effect that affects phosphor based displays. I have also never heard of the micro mirror engines getting "slow". I have heard of them getting stuck though, which gives the appearance of dead or stuck pixels that you most often see in LCDs.

So, if you are reading this thread because you are searching for ghosting issues, DLP is burn in and ghost free. Ghosting is when the polarized grid in LCD panels can't change state fast enough to keep up with the moving image.

But DLP does have the rainbow affect which can appear similar to ghosting with fast movements with high contrast. There are other threads that explain how RBE occurs.

I have noticed that on some projectors, vivid, contrast, and sharpmess settings can make RBE less or more. Which likely explains why the photo setting eased the issue.

This reminds me of my first LCD TV which I still use today. A Sony 40" Bravia with only 60Hz refresh. Most TV content is ghost free for me. But some content has terrible smearing going on that sometimes looks like ghosting, but is really just the crappy compression used on that particular source. In this case for me on that TV, I have found that crushing the blacks and high with higher contrast actually reduces this source issue for me.

So I just wanted to record in this old thread, that for this type of issue, the problem is most likely the source. The test would not be to test the same source on a different display, as that only means a different display handles the source differently. But to try a different source, such as a quality BluRay film, on the same "problem" display.
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