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jarseneau
Joined: 06 Nov 2007
Posts: 323
Location: WI
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| Posted: Tue Mar 17, 2009 5:47 pm Post subject: NEC XG 1352 LC - shifting optical focus?? |
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I've been an NEC XG owner for years. About a year ago I upgraded to a 1352 LC after owning an AC model and I've noticed what seems to be drifting optical focus over time. When I setup optical focus in the first place, I use the Guy Kuo method of defocusing electronically and then using a 3x5 card to check if the phosphor grain from the CRT surface is in focus at the screen. A recent re-check of this had the focus fall at about 6" out from the screen surface.
My guess is that it has some connection with the LC but not sure what to do other than to refocus every few months. I've checked that the sheimflug screws and wingnuts are tight and it all looks fine. Is this common? Doctor, is there a cure?
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Jerry
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MikeEby
Joined: 24 Jun 2007
Posts: 5237
Location: Osceola, Indiana
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| Posted: Tue Mar 17, 2009 6:39 pm Post subject: |
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I have noticed this too on my 1351 especially at higher scan rates. It seems like it will “drift in” but it can take several hours. Recently I reloaded my HTPC with Windows 7 and just for fun of it I setup 1600X900@72hz the focus seems to “drift in” much quicker. It’s purely subjective but it seems like Windows 7 scales 1080p to 1600X900@72hz much better then Vista did and right now that is the resolution I’m running.
Mike
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Doing HD since the last century!
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perisoft
Joined: 29 Aug 2007
Posts: 2920
Location: Ithaca, NY
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| Posted: Tue Mar 17, 2009 7:37 pm Post subject: |
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I would presume this has something to do with the index of refraction varying with temperature. Is that the case?
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MikeEby
Joined: 24 Jun 2007
Posts: 5237
Location: Osceola, Indiana
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| Posted: Tue Mar 17, 2009 7:38 pm Post subject: |
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| perisoft wrote: | | index of refraction varying with temperature. Is that the case? |
LOL...yes.
Mike
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perisoft
Joined: 29 Aug 2007
Posts: 2920
Location: Ithaca, NY
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| Posted: Tue Mar 17, 2009 7:58 pm Post subject: |
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| MikeEby wrote: | | perisoft wrote: | | index of refraction varying with temperature. Is that the case? |
LOL...yes.
Mike |
Which would imply that varying scanrates heat the projector up at different rates - but what you're saying suggests that higher scanrates take longer to get the projector to equilibrium...
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jarseneau
Joined: 06 Nov 2007
Posts: 323
Location: WI
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| Posted: Tue Mar 17, 2009 9:09 pm Post subject: |
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Hours to settle.. that would explain how I would have adjusted it and then come back later to see it out. It's reassuring that it's not just me.
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Jerry
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Tue Mar 17, 2009 10:33 pm Post subject: |
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I've never noticed it change.
Now you have me paranoid....it's been a few years since I set it, and I've never touched the optical focus.
Have you guys got your lens screws done up adequately tight?
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Gary M.
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| Posted: Wed Mar 18, 2009 8:44 pm Post subject: |
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I used to have a Barco 808s that did this every day, it would always move off the exact amount and it was very minor and never more, set the focus for nice grain and it is gone in a few hours, I tried compensating in the other direction the exact amount and that didn't work, tried tightening to near breakage and the opposite leaving the lock nuts loose, nothing I ever tried worked, I was doing 1080i/60hz
there are units out there that have shifting optical focus and from my experience it can't be fixed, there was a story on AVS of a shifting G70 that never would act right and stay focused
-Gary
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