Stretching algorithms?

Discussion in 'Displays' started by Robert K, Dec 17, 2003.

  1. Robert K

    Robert K Agent

    Dec 8, 2003
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    I've come to realize that most my TV watching (95%)will be of 4:3 material (due to limited cable offerings). I would still buy a 16:9 as I love DVDs and that alone merits a 16:9 for me. My TV choice right now would be a SONY CRT based 65" RPTV.

    Of the CRT based RPTVs, does a mfr or model (or all) offer approaches for 4:3 screen fill that do not distort or minimally distort to fill a 16:9 screen. Would visual distortion be imperceptible except for visual clues like a ticker bar running across the bottom of the screen?

    I don't see this discussed or rated in the TV reviews I have read.

    This has come to be important for me for two reasons:
    1) To prevent screen burn I really need to use the stretched mode.
    2) Past screen fills I have seen were horrific to view, fat and squatty. If thats still my choice for screen fill, Im going to have to consider a LCD RPTV instead to prevent screen burn.

    Any way, I thought worth a thread to discuss this aspect of big screens that I don't see talked to much.

    I hope interesting enough to respond to.

    thank you in advance for any thoughts,

  2. Steve Schaffer

    Steve Schaffer Producer

    Apr 15, 1999
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    All widescreen sets offer a variety of ways to modify a 4/3 picture to fill the screen horizontally. Without exception it is impossible to modify the picture without either distorting the geometry or cutting off the top and bottom of the picture.

    All mfgs offer the following modes:

    1: unmodified 4/3 picture in screen center with gray bars on sides. If you take the set out of torch mode (calibrate with a test disc, run contrast under 40% or so) and watch a considerable amount of true widescreen material the gray bars instead of black will go a long way toward preventing burn in.

    2: Full (Sony designation as well as most other mfgs) This is the native mode for anamorphic dvd and the mode the set will default to when fed a true HD scanrate. 4/3 material in this mode will be uniformly stretched sideways, no picture lost off top or bottom, everything looks short and fat.

    3: Zoom This is also called different things by some mfgs.
    This mode is a uniform vertical and horizontal stretch.
    No geometric distortion occurs but top and bottom of 4/3 images is cut off. This is the mode one would use for non-anamorphic widescreen dvds if one does not have a player capable of scaling the pic up. It's also the mode used for displaying letterboxed movies on 4/3 stations. Most crt sets achieve this by actually spreading out the raster so scanlines will be more visible in this mode. Most all sets also allow the picture to be scrolled vertically up or down to make newscrawls and such visible.

    4: Variable stretch--called WideZoom by Sony. This mode is the one that differs the most from one mfg to another.
    This mode basically stretches more at the sides of the picture than in the center but different mfgs add different modifications to minimize the resulting funhouse mirror effect.

    Hitachi and Mitsubishi a couple of years ago (haven't checked them out lately) did this very badly. Stuff in the center was normal, lots of stretch occurred at the sides. Nasty looking. Mits and Hitachi may have improved on this lately.

    Toshiba, Pioneer, and Sony do it much better. Sony, for example, still has a minimal amount of horizontal stretch in the center, virtually undetectable. They also do a bit of vertical zooming but with some compression at top and bottom. As a result the horizontal stretch at the sides is not nearly as extreme as on the older Hitachis and Mits.
    In most sitcoms and such it's virtually invisible. Since there is partial vertical stretch the scroll feature (remember Zoom mode?) is also available. Nescrawls do reveal what's going on but for most shows you don't really notice the geometric distortion much and soon get used to it.

    I beleive Toshiba has 2 different versions of variable stretch available on all their sets, but could be wrong.

    Some sets may also have a "Zoom 1" and "Zoom 2" choice. One Zoom being an equal vertical and horizontal, one being full horizontal but only half vertical (stuff is still short and fat but not as severely as in Full, which is a horizontal only stretch.

    I've had a Sony 16/9 rptv for a couple of years now and have found Widezoom to be ok for casual viewing of news, sitcoms, etc. For serious viewing of 4/3 stuff like old movies I use the Normal (Gray Bar) mode. I've got an HD box that has the "zoom 1" and "zoom 2" digitally so there's no raster expansion, and find that a lot of 4/3 stuff looks pretty well framed when displayed in an equal zoom mode. Again, serious movie watching is done in gray bar mode on the box.

    Overall about a third of my 4/3 viewing is in graybar mode, the rest either zoomed or stretched. This is about half the overall use of the set, the rest being Full HD or anamorphic dvd, the latter mostly 2:35 aspect ratio so there's still black bars on a 1:78 set. I have my contrast set around 40-45% and calibrated with Avia. No burn in whatsoever in 26 months of use.

    If you can, go to a store that has a native 4/3 source available on their widescreen sets and check out the variable stretch modes yourself to see what's easiest to live with.
  3. Jeff Gatie

    Jeff Gatie Lead Actor

    Aug 19, 2002
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    Toshibas have "Theaterwide 1" and "Theaterwide 3" (Theaterwide 2 is zoom and crop for non-anamorphic DVD's and widescreen NTSC). "1" is the variable stretch (very goo IMHO), "3" is a uniform stretch with a slight vertical crop, plus scrolling. Not as stretched as Full, not as cropped as the Theaterwide 2 zoom and crop. I use all three depending on the source and found they equal or better the modes on other sets.
  4. John S

    John S Producer

    Nov 4, 2003
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    In looking at this very issue, it actually drove me to a large 4:3 set of 60". Now I find myself wanting to watch HD and DVD's in the sets native 16:9 mode.

    The different plus's and minus's on each side of this 16:9 -vs- 4:3 really is enough to drive one crazy.

    I have at least one IMAX DVD, that is native 4:3, and man, does it ever give you that IMAX experience on this set.

    I'm not a fan of stretch modes in general myself, I do not find them usefull at all for my tastes.

    I still think I would of had to get a 73" widescreen to make me happy with my 4:3 material, but not near as much as I thought I would. I do love my new HDTV though. After only two nights with it now, I find myself, just sort of gawking at the PQ, more than really watching / enjoying the actual content, I would assume that wears off with time right??? lol

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