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Discussion Starter #1
Ok - its getting close to deciding what distance I will be going back so I can plan my hidden wiring.

Please keep this constructive. My goal is to "try" and get the best picture with the worn tubes before I decide to retube later this year. If you want to approach it as "here is what I would do, thats fine too)


Lets assume I am not changing the mounting method, the tubes, rebuilding the tubes or anything like that right now.


I will give the facts and lets see what the best option would be for anyone in my situation.


Table mount - screen size omitted because everyone freaks out if you go 8'1" or larger. No need to comment on size. Screen right now will be either...


This decision will be contingent on price alone.


1. New smooth foam rollered primed drywall with Behr UPW or KILZ 2 outside chance a DIY Goo copy (ala scoobi, crma, Mississippi posts)

2. High Power on DIY frame (waiting for Jason's quote)


Heres it is:

What are my options to remove the 4:3 burn from a 16:9 view? Note: The burn is an even pattern no text burn in.


Which option produces a better picture, clarity, color etc?


Which option hurts the tubes further, is this a concern?


Is it more advisable to live with the burn in and maximize the raster (whatever that means, I am new)


If the projector needs to go back further than the published spec - whats an average amount...10" back, 12" back 15" back


If I use the "move it back over by der" method does everything else have to be done by eye during the setup?


How does this effect alignment? Convergence? Angle of lense? Brightness? Anything I need to know before beginning on ALL these subjects?


I think that about covers it.


Hopefully I will be able to make a solid decision based on your experiences and others can use this post as a reference.
 

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If the burn is even, you will want to set your raster within the burn pattern, so you don't see the difference between the clean and worn part of the tube. If they are spot burns from some desktop application, you will see them, nothing you can do about it.


Obviously the smaller the raster on the tube, the less brightness and resolution you will have and the projector will need to be set further back to fill the screen. The further back you set the projector, the less bright your image will be on the screen. Bit of a catch 22.


Each time you move the projector, you will need to at the very least re-do the convergence and focus. If more than a few inches, you will likely need to do a mechanical allignment as well.
 

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The reverse watermark/digital masking technique can be of use to you if you're runnign an HTPC. Refer to the threads on that subject for more info. In short, you're making a watermark of the burn pattern and displaying it in negative format, resulting in the brighter parts of the phosphor being driven less hard, thereby equalizing the brightness across the whole screen. You lose a little in the way of total brightness capability, but the screen burn can be, at least in theory, TOTALLY eliminated.


CJ
 

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Discussion Starter #4
Ok - now that sounds complicated as all hell - but I finally understand what you are saying.


Feed a sound wave the opposite and it cancels out - the same principle!


Hmm - this would allow me to use the full raster right?


This sounds like a really good option for my situation.
 

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To do it, first you need to perfectly align and converge your projector. The convergence needs to be STABLE, too.


Now you need a good digital camera capable of taking high resolution photos of your screen, and a tripod.


Project a full screen pure white field onto your screen. Take a reference photo of it. Now take photos of the screen with only one CRT displaying a picture at a time. You want pure red, green, and blue fields showing, and nothing else. Whether you can do this from your remote control, via internal switches, or by just covering the other lenses is going to depend on your projector brand and model. On a Marquee, you'd just hit the COLOR button on the remote and then hit the 1, 2, or 3 key. (Actually, 1 thru 8 all do something on a Marquee.)


Snap a picture of each pure R, G, and B color field.


Download the images to your PC. Presuming that you have PhotoShop or some other software that will allow you to manipulate the image and then create a mask from it, you would then create said mask by first turning each image into a negative, and then playing with the brightness and contrast (and maybe the gamma) settings until the mask exactly cancels out the burn on a given tube.


Of course, you would do this with your PC actually hooked up to the projector so you can see your results in real time.


When the resulting image is free of burn-induced intensity variations, you've got it. Save your work. Now you can use that work as a watermark of sorts, using the mask feature available in some DVD software, as I understand it. (I haven't actually done this myself, lacking both a suitably powerful HTPC and also the software to make the masks with, plus I have no burn issues worth addressing anyway.)


This can also be used to iron out the "hot spot" in the central portion of the projected image. The dimmer outer sections of the image can be boosted slightly (well, you actually make the center dimmer to match the outsides) and you end up with a highly uniform white field.


But, your convergence has to be stable. If it drifts, you'll have to move it back to where it was or your mask will be virtually useless, if not actually worse than no mask at all. It has to be well aligned to the burn for it to have the desired smoothing effect.


CJ
 

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Discussion Starter #6
Quote:
Originally posted by cmjohnson

worse than no mask at all. It has to be well aligned to the burn for it to have the desired smoothing effect.


CJ [/b]
Ok well this sounds good. I am going to have to setup from scratch anyway and get aligned and converged in the room (new room)


This way I can utilize the most raster ( I think) and just set up like normal.


Then work on what your saying.


This would also allow me to leave my projector at the correct distance from the screen according to the manuals which in my case is very important!


If I have any of this wrong - someone please correct me.
 

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Just make sure that you post before and after photos of the screen with and without the masking trick, once you've got it working!


CJ
 

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CJ,


Good stuff, I saw some conversation on the mask, but didn't pay much attention to it as I run a scaler and it was HTPC related. It sounds like a pain to figure out and get right, but could work really well.


Jay
 

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I for one choose the "live with the burn" route. For me, it was barely visable and the guests really dont' notice.... Gonna retube as well in the future.


I say use that phosor! Unless the burn is hideous, I have a hard time with the concept of abusing the rest of the surface thats fresh.


Marc
 

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Discussion Starter #10
Quote:
Originally posted by genmax
I for one choose the "live with the burn" route. For me, it was barely visable and the guests really dont' notice.... Gonna retube as well in the future.


I say use that phosor! Unless the burn is hideous, I have a hard time with the concept of abusing the rest of the surface thats fresh.


Marc
Guests would not matter...I have to look at it more than guests.


I dont think I would like any white or bright scene to show discoloration of one or both sides of the picture.


Even when I threw up a picture whe I got it home (completely setup wrong) I could see the discoloration here and there - when I white screened it - bammo its there both sides.
 

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FYI, and just in case anyone might have misunderstood it, the watermark masking technique doesn't attempt to burn the phosphors evenly. Far from it. It drives burned phosphor at normal levels and drives unburned phosphor at REDUCED levels, to keep the average output the same.


A contrast-enhanced original positive of the screen could be used to even out the burn by intentionally burning the rest of the screen.


CJ




CJ
 
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