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5 misconceptions of panel projectors

Discussion in 'Projectors, Screens & Video Processors' started by Jeff, Jan 7, 2002.

  1. Jeff

    Jeff
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    Panel projectors are plug'n'play.

    There is a vast array of changes that can be made to a panel projector in order to get a better picture. Stock settings are usually well out. Gamma tables can be modified. Colour levels can be changed. People like Thumper and KBK make a living out of calibrating and performing hardware mods on these things.

    Panel projector work well with ambient light.

    Well they are better at it than CRTs, but they still work much better in a light controlled room with dark walls and ceiling.

    Panel projectors are best run at native resolution.

    I wouldn't have guest this one, but the down scalling (at least on my projector) is pretty good. If you feed it something like 1440x960 which a DVD sweet spot being 2 x 720x480 and let the projector down scale to 1024x768, you get a better picture than a PC scalling to 1024x768 and pixel matched to the projector.

    Panel projectors work well with large screens.

    I take the oposite view, while the image might be brighter allowing larger screens to be an option, you do need to have a larger screen to viewing distance ratio than with CRT. Also a quality screen with good black velvet masking is just as important as with CRTs.

    CRTs are better than panel projectors

    I'm not silly enough to believe that my little Plus DLP projector is as good as a Barco 808, but then it only cost about £2000 new. I can't think of many price points (if any) where a new CRT will outperform an equivalently priced panel projector. Even if you take the price thing out, how does a Cinemax compare with a QXGA DILA ?(I don't know by the way). That said, I do understand that 2nd hand CRTs are very good and offer great value for money.


    Jeff
     
  2. Nic Rhodes

    Nic Rhodes
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    Good common sense. Well written. A reality check.
     
  3. tryingtimes

    tryingtimes
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    WOW this is interesting. Do you see a technical explanation for this?
    I find it hard to see this as just being down to the high quality of the projector's downscale - especially when you see how well they upscale :)
    Obviously, you are seeing a better image and we have no doubts that kryton is as good as hcpc gets but it would be interesting to find if this can be repeated with other projectors.
     
  4. Jeff

    Jeff
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    HTPC DVD scalling has been very well covered on AVS, it turns out that our video cards don't do a great job when when scalling from 720x480 to something like 1024x768. 1440x960 is much easier to do because its exactly 2X DVD resolution. They have also found out that once you get passed the 2X resolution then exact multiples don't really matter, ie 1900x1080 also looks good. The idea to try higher non-native resolutions came from KBK, I all ways take what KBK says with a BIG pinch of salt, but this is an easy thing to try out. When I first tried this I couldn't really tell much of a difference which was a suprise in itself. The clincher was Zorgs shirt in the fifth element superbit. At native 1024x768 you can see that the thin lines on his shirt are slightly jagged. At 1440x960 and down scalled to 1024x768 by the projector the lines are completely smooth. There are 2 other benefits that I didn't expect and can't explain. The first is a considerbly reduction in visible rainbows (others have reported this too), the other is that I was getting an annoying problem where if you have a completely black scene that lasts more than a second or 2 (unbreakable has this when Bruce falls into the swimming pool) the projector goes out of sync for a second and might only show the top or bottom of the screen, after about a second all is normal again. Mid film it is very rare, but I often got the problem between the film companies logo and when the film starts. This problem has now mostly gone away.
     
  5. Mr.D

    Mr.D
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    Two main reasons the second one being almost an urban myth in certain circles.

    When you upscale an image then downscale you are effectively averaging out interpolation errors. This is actually similar in principle to anti-aliasing. However there is normally some softening of the image that makes this less ideal than using better more sopshisticated filters to scale.

    Second one is a bit tenuous these days. Scaling an image in whole numbers : some go as far to say even rather than odd ,supposedly makes life easier for more simplistic resizing filters. To be honest this went out the window with the ark but I suppose it might have some validity if very simple filtering is being used. ie some inbuilt scaling.

    Softening an image on sizing up may in fact be preferable to maintaining sharpness at the risk of exacerbated aliasing/jaggies.
    On occasion for similar processes I'll use a bilinear in preference to a sinc or minify filter as whilst the latter preserve more accurate detail relationship to the original image the can contribute towards aliasing and pixel grain.
     
  6. Roland @ B4

    Roland @ B4
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    It's an iteresting effect by upping then downing the image. It was used a good deal on the early LCD professional projectors in putting a higher resoultion scalled source because it was easier to throw away and join pixels than it is to split them up. It certainly got rid of the jaggies but it softend the image.
     
  7. Roland @ B4

    Roland @ B4
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    Good man - delivery address?
     
  8. JohnAd

    JohnAd
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    Jeff

    Interesting observation with the scaling.

    One possible thing to throw into the mixer is that some graphics cards have problems with scaling the UV bits of the YUV signal they get sent properly, blight on AVS was going on about this at one point. This bug may be minimized at even scaling factors and so overall you might get a better image.

    If you said the effect was noticable on b&w films as well this would be ruled out.

    John
     
  9. Jeff

    Jeff
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    I just checked, out of 200+ DVDs the closest I get to a B&W film is the Matrix. :)
     
  10. tryingtimes

    tryingtimes
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    LOL:D
     
  11. Jeff

    Jeff
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    My little DLP is having an operation tomorrow to help reduce black level and reduce noise, wish him luck. I promise to be gentle. :devil:
     
  12. Gary Lightfoot

    Gary Lightfoot
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    Hi Jeff,

    Will this be a secret thingy, or are you going to share it all with us? :) (pics would be nice ;) )

    I'll keep my fingers crossed and hope for a full recovery!!

    Talking of scaling, I noticed something quite interesting with my old MPact2 HTPC. If I let the software do the scaling, there would be no jaggies. I believe it was downconverting the image to 340 lines, then upscaling/interpolating to (800 x) 450.

    If I output an anamorphic image, then used YXY to convert it to 450, the 30 droppedlines were very noticable. Increasing the height to 480 (losing a few pixels off each side in the process due to keeping the correct aspect ratio) eliminated the dropped lines, and the image was sharper.

    This wasn't really an option with PAL 576 DVDs do to the amount of image that was lost each side (loads).

    I've just upgraded to a Radeon and using Zoom and the ATI filters, but I haven't looked into the scaling situation yet. The image is far better than I could have imagined, and I'm not sure if I'm getting a down up conversion or what! :)

    Gary.
     
  13. JohnAd

    JohnAd
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    Jeff

    I'd forgotten your dislike of older films...

    You could try turning overlay saturation down to 0 to fake it.

    Good luck with the mods

    John
     
  14. Jeff

    Jeff
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    Nothing secret, I'm looking at doing a few mods, for know I'm looking at doing a colour wheel mod to blank out the clear section of the wheel. I'm also going to remove the grill that covers the fans and the wire mess in the back of the lamp, the idea being that if I improve air flow around the fans I should be able to decrease the noise.
     
  15. Jeff

    Jeff
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    ITS ALIVE!!!! HA HA HA

    Well it still works which is a miracle in itself. Th first mod I did was to cover the clear section, I did so with a silver permanent marker so that blocked light is returned to the lamp and reused. After the mod colours are more vivid, redsg look I bit strong so a recalibration looks in order. Contrast has improved maybe about 20% (these things are dificult to judge with the naked eye). The second mod was to remove the case grill in front of the fans and the mesh on the back of the lamp. It still sounds noisy, but less harsh. The 3rd mod was to remove the front part of the case and construct a replacement cover that lets me get the lens closer to my ISCO, this also worked by reduceing distortion.

    Anyway its getting late so thats all for now.

    Jeff
     
  16. Mr.D

    Mr.D
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    Nice one Jeff.
    I'm all for "user intervention" !
     

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