Can't see all the picture!!

Discussion in 'Projectors, Screens & Video Processors' started by Donnacha, Sep 3, 2002.

  1. Donnacha

    Donnacha
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    Hi,

    I'm running a PTae100 (which I got at the weekend, and pleased!!) fed by a pioneer dv535 with a s-vid cable. At the moment I'm only projecting ont a sheet as I haven't set the room up yet and I couldn't wait to see it in action.

    Anyway, while messing about with the picture settings in the menu I noticed that during The Phantom Menace i wasn't seeing all the picture. When I adjusted the horizontal position left or right there was more picture. It looked like the image was cropped at each end, therefore I am missing out on all the image.

    The PJ is set to 16:9. Anyone else notice this, and is there any way round it? Would the HCPC route fix this, as I seem to be able to see all the image on my PC. Or is it the PJ.

    Any help, greatly appreciated.

    Cheers

    Donnacha
     
  2. Gojira

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    Have you tried reducing the zoom by adjusting the lens?

    Or changing the viewing aspect?

    (Simple I know but that's the first things I would check)
     
  3. Donnacha

    Donnacha
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    Thanks for the reply - If I explain clearer then it might make more sense!!

    Episode 1 - During the Duel of the Fates, Darth Maul uses the force to pick up an object and fling it at the controls of a door in order to open it! OK?

    On the PJ and my Panasonic TV I can see this happening at the edge of the screen, just ! There is the explosion half on / off the screen.

    On my PC I can see it all clearly at the side, not half on /off.

    Does this make sense? So when I go into H-Position in the picture menu on the Panny PJ and move the image left or right, there seems to be plenty of image form the film that is lost at the sides.

    Clear (as mud)!!!

    Any suggestions on why this is, or is this a good reason to go HCPC via VGA?

    Thanks

    Donnacha
     
  4. karkus30

    karkus30
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    You have set the DVD player to 16:9 format ?
     
  5. CSGardner

    CSGardner
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    That sounds like OVERSCAN to me .. i.e. the intentional blanking of the left and right edges of the image.

    Its easy to confirm - IF you have a test disc such as Video Essentials. On that disc, there is an OVERSCAN test image - which allows you to measure exactly how much overscan you have on your display device.

    I can confirm that the AE100 using the VGA input shows the whole image, but using the COMPONENT input, cuts about 5% off from left and right. I suspect S-Video input would be similar.

    Chas
     
  6. Donnacha

    Donnacha
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    Thanks Chas,

    I suspect you're right, as it isn't much of the image that's missing, about 5%.

    I'm going to try and get hold of a VGA cable and test with my PC.

    Karkus30 - yes it is set to 16:9.

    I'll post up my result after a comparison. Its strange that this doesn't seem to be something that is mentioned in the Standalone dvd player vs. HCPC.

    Thanks for the help

    Donnacha
     
  7. Bert Coules

    Bert Coules
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    Chas wrote:

    I can confirm that the AE100 using the VGA input shows the whole image, but using the COMPONENT input, cuts about 5% off from left and right. I suspect S-Video input would be similar.

    If you're right about the s-video input, this explains my absolute (but baffling) conviction that my widescreen images from DVD are not in exactly the same aspect ratio they were in the cinema. Thank you!

    I'll check this today.

    Bert
    www.bertcoules.co.uk
     
  8. Donnacha

    Donnacha
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    Its not just me then !! Thank God for that !
     
  9. snelly

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    I can understand why this (overscan) occurs with broadcast signals to CRT TV's but...

    I am really annoyed that this happens to the projectors. I guess that even if the native signal coming out of the back of your DVD was identical to the panny and you connected via svideo or component the internal scaler will come into play. Makes me wonder if it is worth bothering with a PS DVD player or just to go straight for an HCPC after all - something I wanted to avoid initially.
     
  10. Chris Frost

    Chris Frost
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    Being able to display the entire video image without overscan can be equally frustrating!

    Common problems include the picture size changing on TV broadcasts as shots change from studio to outside broadcast and back. This is particularly bad with satellite and cable channels as they all use slightly different phase settings on broadcast.

    Other quirks are that you might see bits of film & sound equipment popping into the edge of the frame. The classic is the overhead boom mic dropping into shot - this can really ruin the illusion that our heros are out in the wildness miles from civilisation.:eek:

    I agree that we want to see as much of the picture as the director intended - that's why I and many HC enthusiasts prefer Widescreen. But be careful you don't go too far, or you'll end up watching for the mistakes and missing the film.:)

    Regards
     
  11. snelly

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    Thanks Chris thats interesting. I suppose the overscan does give them some margin of error. However if a director actually places visuals in these extremes then we are going to miss out.

    I accept this for broadcast as I said in my original post...But when you have a source like DVD that has hopefully been skillfully mastered in a studio and any glitches removed it would be nice to see the whole pic. Perhaps an on off overscan function or even just a good old H-Size adjustment...That said I still have not worked out how to do this on my new portable Sony 14" TV :confused:

    It really bugs me though that things might get scaled like this :mad:

    Tim
     
  12. Chris Frost

    Chris Frost
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    Snelly, even if the film is transfered to DVD correctly (and that's a big if), there are still several steps to getting a viewable picture. These can increase the amount of overscan without you realising.

    Nearly all DVD players apply a small amount of pixel cropping. This is what Chas Gardner was refering to.

    This cropped signal then gets to your TV or projector, where it is probably cropped again! You can see how the compound errors mount up.

    With a video system the manufacturers are working with a "lowest common demonitor" approach. That is not to say quality suffers, just that they need to ensure that the image fits everything from a high quality W/S TV down to a basic portable telly. The trade off is overscan.

    A HTPC system will give you the entire DVD image including the areas beyond the overcsan limit. It is then up to you to decide how to frame that on your projector.

    Trying to do the same on a TV is going to be difficult. Unlike PC monitors, domestic TV tubes aren't designed to do width underscan for long periods. Professional TV monitors can, but then a 15" 4:3 set costs around £1000.

    As much as it annoys us HC enthusiasts, we have to accept that the average man in the street can't understand what all the fuss is about.

    Regards
     
  13. snelly

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    Point taken Chris and perhaps I was being fussy and expecting too much of what is after all domestic equipment :blush:

    When you say a domestic Tube can't handle underscan - I am not sure I fully understand what you mean. I could imagine that it might damage the tube if the electron beam strayed off the phosphor onto - I dont know some structural part or something...but wouldn't udnerscan imply that *all* the pic is displayed on the tube, possibly with black vertical bands?:confused:

    I guess why I am peaved is that I can see no reason why the Panny could not have a H-Size adjustment. I can't see how it would cost panasonic anything significant to implement it and yet it is not there.

    Tim
     
  14. Guest

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    Using a HTPC you can eliminate overscan, but as Chris mentioned, some overscan is desirable. But there are other reasons why action my occur at (or just over) the egde of your screen.

    Actually showing the picture completely as the director intended, can be a a bit hard. This will become clear as you learn a little bit about film formats and the process of matting a film.

    As you might have seen most DVDs are either formatted as 1.33:1, 1:85:1 or 2.35:1 aspect ratio. There are, however, a lot of aspect ratios and techniques than can be used to produce a film.

    The final aspect ratio of a film depends on:
    -Method of filming. There are some exotic techiniques for filming. Cinerama f.e. uses 3 cameras to produce 1 frame (and 3 projectors to produce 1 picture).
    -The negative size and film size. Widely used is the Academy format (4:3).
    -Matting. A lot of films are (still) shot in Academy format. During post production a process called soft matting is applied whereby only the part that is to be shown on the print is left uncovered. There really isn't a fixed aspect ratio the filmmaker has to adhere to. Most used are 1:85:1 and 1:66:1

    There is one other issue: a widescreen TV or Projector has an aspect ratio of 16:9 (ie 1.77:1). This format is only recently starting to get used by filmmakers, as it previously only was available as a "non-standard" aspect ratio by using soft matting.

    As you can see there are a variety of image formats, and almost none will fit your 16:9 image perfectly. As a result, DVD producers have to create some (or a LOT !) matting (and a bit of resizing) of their own to fit the usual DVD aspect ratios, and the resulting picture on your television or projector is almost never the same as in the cinema.

    For a list of image formats see this site : http://www.widescreen.org/aspect_ratios.shtml (Missing from the list is IMAX which has an aspect ratio of 1.337:1 (not quite 4:3))

    (edit:some typos)
     
  15. snelly

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    Mr Custard,

    Thanks I was aware of some of these issues but not to that level of detail. I appreciate that as the AR of our monitor device is likely to be fixed in the case of a PJ or TV.

    What I want to make sure of is...

    1)I am seeing the film at the correct aspect ratio i.e a circle is still a circle!

    2)I am viewing everything that editorially has been left in.

    Basically the implication of this is that if the source material has different AR to your monitor device then you will end up with black (or grey for LCD;) ) bars - but that I can live with, I don't like missing out on part of the picture.

    It is dawning on me just how much there is still to learn in the AV world. And also how the world would be a better place with more open standards...

    Thanks for the input guys I have found it really interesting and educational :)

    Tim
     
  16. Chris Frost

    Chris Frost
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    To be honest Tim I don't fully understand it myself, but I can take an educated guess that it is to do with the energy generated by the electron beam when it parks at the end of the retrace line before scanning the next image line.

    If this was parked on the viewable part of the shadow mask/aperture grill of the TV tube it would create a heating effect that could distort the shadow mask. The effect would look like really bad misconvergence.

    Regards
     
  17. Guest

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    1) you can be reasonably sure of that ;)

    2) just use a device that gives you control over the output or input (or both) and you should be OK (ie HTPC (control over the output) or CRT projector (control over the input)). Using a standard DVD player with a digital projector gives you neither control over the output nor the input, so you'll have to suffer at least some cropping.
     
  18. Donnacha

    Donnacha
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    Great info guys - it has given me another good reason to move to HCPC - eventually!

    I'd always noticed this on my TV before I got the pj that some of the action at the edge was a little off-screen. I was surprised to see this on the PJ. However as I can see everything intended on the PC I now know what route to go in the future.

    Thanks for the input

    Donnacha
     

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