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Discussion in 'Electronic Repair' started by Arfa Daily, Jun 16, 2007.

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  1. Arfa Daily

    Arfa Daily Guest

    I went to a cinema last night that I hadn't been to before, to see Ocean's
    13. We sat about half way up the theatre, so not too close. Both of us
    commented that the picture didn't look *quite* in focus, although that
    didn't seem to quite cover it. When the picture stood still though, it was
    pin sharp. During the advert session, they mentioned that some sporting
    event or other, was going to be covered live via satellite, which got me
    thinking that this must be an *electronic* cinema, using DLP projectors. It
    then occured to me that what we were seeing as being 'out of focus' might
    actually be motion blur, typical of digital display technology. With this in
    mind, when I looked even closer, it seemed to me that the picture was not
    evenly illuminated either - a bit like I see on this widescreen LCD monitor
    that I'm using here. During the main presentation, a film-stock 'scratch'
    appeared at the left side of the screen. However, it went on for a long
    time, and was absolutely dead straight, although it did jump back and forth
    a bit, but very 'precisely'. Also, it's colour seemed to change with the
    surrounding content, so if that was black, the 'scratch' would be white, and
    so on, so I then got to thinking that this might be an error on a line of
    mirrors on the DLP chip. As we left the cinema, I took a look up at the
    booth window, as best I could, and there didn't seem to be any film looping
    around the ceiling that I could see.

    So, does anyone out there work on these DLP projectors - either commercial
    or domestic ? *Was* it one of them that was showing this film ? Are these
    DLP chips slow enough that you can see motion blur ? Was that 'scratch'
    typical of a DLP chip problem ? ( it wasn't there at the beginning, and it
    went away before the end )

    Sorry it's a bit OT, but it seemed like an interesting subject, with a
    potential repair-related angle, and we sometimes have some good discussions
    on here about such things.

  2. I have a DLP rear projector and it certainly has motion artifacts on some
    material. It's most noticeable on TV material that is interlaced
    originally. But then plasma and LCD also have artifacts. You need a decent
    CRT to avoid them. ;-)
  3. Charles

    Charles Guest

    MPEG compression artifacts are very distracting when the scene is changing
    rapidly. Don't know for sure if that is a factor in your post. Satellite
    video seems very prone to this phenomenon.
  4. Arfa Daily

    Arfa Daily Guest

    Yes, I've seen that on satellite channels that use a low bandwidth
    transponder, where the station presumably has to apply severe levels of
    compression to get the data rate down. These are of course the 'cheapo'
    stations that can't afford transponders capable of handling high data rates.
    When you look at stations like QVC which shows very fine detail stuff like
    jewellery, or the premium movie channels, it's much less noticable. I'm also
    well familiar with typical motion artifacts that come from both LCD and
    plasma display technologies. It's the one thing that has stopped me
    replacing my large screen CRT set so far, whilst I hang on and wait to see
    what SED has to offer when it finally hits the market. Word is that the
    drive system required is much less 'digital' than either LCD or plasma, and
    that the individual SED cells are *much* faster. As a result, these displays
    are a lot more 'CRT-like', and don't suffer the typical motion artifacts
    created by the drive electronics.

    Going back to the cinema thing, 'motion artifacts' in the way we
    traditionally understand that term, didn't seem to be what we were seeing.
    Normally, with 35mm film stock, camera pans appear just as they would with
    your own eyes, if you were turning your head. The (apparantly) moving scene
    stays in sharp focus. What we saw on any protracted camera pans, was what
    appeared to be an annoying shift in focus. No pixellation at edges, or
    motion trails on bright or saturated areas. Just what looked like a uniform
    shift in focus over the whole screen. You were actually thinking "boy, my
    eyes are getting bad". But as soon as the pan slowed to a stop, the focus
    was back pin sharp again. It's hard to describe, but it was only a few weeks
    ago when Spiderman came out, that I went to a U.S. cinema - actually one in
    the Orlando area that's been completely refurbished over the last year -
    that was using film (you could see it looping round the ceiling through the
    booth window) and I noticed nothing out of the ordinary, at all. The cinema
    in my town that I usually go to, also uses genuine film, and I haven't
    noticed anything wrong worth commenting on there either, so I'm sure it's
    not just me. Plus the fact that my wife said that she was seeing exactly the
    same thing, and it was she that made the first comment.

    I guess that it might just be the price that we are paying for technological
    advance, but I sure hope that this part of the technology doesn't now get
    considered 'mature', and all development efforts go into other areas. I
    would hate for this to be the future of cinema. In some ways, I think that
    all the 'digital' hype is a bit of a con. Yes, it allows a lot of good
    things like being able to cram lots more channels into the band space,
    eliminating noisy pictures from a poor signal, and ghosting and so on, and
    the digital display technology allows for slimline sets, consuming less
    power etc, but with the best will in the world, if we're absolutely honest,
    the displayed picture doesn't come close to a good CRT set with a good
    analogue signal going in, and the same seems to be true now of film stock
    versus digital cinema projection.

  5. jakdedert

    jakdedert Guest

    Recently helped present the premier of Spiderman 3 at a large
    convention. The projector was--I believe--LCD, the screen, about
    30'x50' (or whatever the correct ratio would be). The film looked great
    in the Aladdin Performance Theater (Vegas). I don't have a 'film'
    reference to compare.

    I have noticed that sharpness in movie presentation has suffered over
    the last decade or so. I recall watching Titanic at my local multiplex
    and being very disappointed at what looked like focus issues, only to
    see the presentation sharpen up for static scenes.

    I think it's just an indication that the art still requires an effort to
    suspend disbelief. For some reason, I've never experienced an IMAX
    presentation. I'm afraid I'd be disappointed. Despite all the hype
    about hi-def TV, I'm still not all that impressed so far.


  6. Arfa Daily

    Arfa Daily Guest

    That sounds like the same thing on the Titanic show,Jak. I've seen IMAX film
    presentations, and they are stunning. We've also got some HD transmissions
    on sat here now and, leaving aside the motion artifacts from the actual
    display technology, I think that they look pretty good,but I'm not sure
    that's good enough for me to want to put my hand in my pocket to pay the
    extra subscription.

    Is Alladin's refurb finished yet ? It was still in progress when I was there
    last year. Are you based in Vegas ?

  7. Ron(UK)

    Ron(UK) Guest

    I noticed on my mates super mega expensive Sony HD giant flatscreen,
    (which he was enjoying showing off to me using Sky`s HD demo channels),
    that only the stationary parts of the picture were really sharp, as you
    say, pans seemed to me to leave a streaky mess and the way the picture
    seemed to pop back into super sharp focus when the motion stopped, I
    found disturbing - I wouldn`t have been happy if it had been a 100 quid
    telly, but as a top of the range state of the art mega expensive piece
    of kit, I was definitely disappointed.
    He doesn't seem to notice anything wrong, he`s very happy with the quality.

  8. Eeyore

    Eeyore Guest

    Yes, that's how video compression works. That's where the high data rates are (in
    the moving bits).

    " He doesn't seem to notice anything wrong " is how they sell it.

  9. Ron(UK)

    Ron(UK) Guest

    They wouldn't be selling one to me then!

  10. Eeyore

    Eeyore Guest

    It's very disappointing.

    Quality has been sacrificed so we can have 500 channels of brain-dead blandness.

  11. Arfa Daily

    Arfa Daily Guest

    But I don't see why we should have to endure this at the cinema, where it
    must be just about distribution costs ( and possibly being able to show some
    live moronic football or somesuch occasionally ). 35mm film suffers from no
    such problems, so if they are now using electronic projectors, and this is
    as good as they're going to get ( coz I guess that the micro-mirrors
    actually have significant inertial mass, as well as suspension resistance,
    both of which which will limit the maximum transition speed of them ), then
    I think that cinema has taken one giant step backwards. It's not as if it's
    cheap to go. For the two of us, with a bucket of post-mix Coke, that
    actually tasted like watered down toothpaste died black, and a hot dog that
    did my stomach no good at all, we got about 20 pence change out of twenty
    quid. Compare this to the cinema we went to in the U.S. a few weeks back,
    where the admission was $6.50 each, and that came with a free sack of
    popcorn and about a gallon of very acceptable Pepsi AND the film was shown
    from proper 35mm stock ...

    I did a quick bit of looking up on these DLP cinema grade projectors, and it
    seems that the horizontal resolution of the DLP chip is 2k, with a maximum
    screen width of around 70 feet. that makes pixels in the order of about a
    half inch, which seems potentially quite big ??

  12. I'd have thought it child's play to make those mirrors move rather faster
    than a projector shutter. ;-)

    Trouble with 35mm film is the cost of the prints and the susceptibility to
  13. jakdedert

    jakdedert Guest

    I have an IMAX here in Nashville. I'll have to brave the crowds some
    time. I've seen hi-def and not been 'that' impressed. OTOH, I'm
    comparing NTSC, so your mileage would be different.
    The casino has been sold to Planet Hollywood, and is under expansion,
    but the theater--though attached--is still Aladdin. Very nice facility
    with VDOSC sound and extensive lighting rig. Despite the quality of the
    in-house audio, the movie people insisted on bringing their own,
    consisting of big bass bins with old 4' square JBL constant-directivity
    horns with a smaller JBL horn mounted coaxially for high end. I think
    they were concerned that they wouldn't be able to match the surround
    gear they brought with the house system.

    I was working a convention in Vegas. Spidey was part of the
    entertainment, along with Hall & Oates, Jay Leno and the Blue Man Group.

  14. jakdedert

    jakdedert Guest

    I don't get to movies much, but the last time I took two 10yo's I
    forbade them to buy goodies as we had just stopped for treats
    beforehand. They asked if they could at least have a bottle of water,
    so I thought 'what the heck' and got one for myself as well.

    Total cost (just for the water): $10.50.

    I don't think the cineplex I usually frequent--and where I saw
    Titanic--could have been digital as far back as that. It must have been
    film. I think the issue lies in shooting the CG (computer generated)
    I didn't actually ask the resolution, as I had numerous other things to
    attend; but I did see the light box, which used a 6 kilowatt lamp. The
    projector was made, IIRC, by NEC. The picture overall was actually
    superb, but did suffer the issues under discussion. Whether that was in
    the production or projection, I couldn't say.

  15. James Sweet

    James Sweet Guest

    I feel the same about HDTV for the most part, but IMAX is really something
    else. There's no comparison between standard cinema and IMAX, it's amazing.
    Most of the IMAX movies I've seen have not been regular movies but features
    relating to science and technology.
  16. Arfa Daily

    Arfa Daily Guest

    Likewise. There's a good IMAX theatre at the NASA complex in Florida that
    shows some stunning views of the earth from space, and a particularly
    impressive sequence containing an 'astronaut's eye view' sliding down the
    escape wire from the top of a launch gantry. That's an interesting point
    that Dave P makes above, about the mirrors being faster than the inter-frame
    shutter on a conventional film projector. I wonder if the difference is that
    the whole frame is rapidly blanked each time, then snapped back on as a
    whole frame with the new-position in the pan, as opposed to 'waves' of
    micromirrors moving *with* the pan. Perhaps the human eye is better at
    integrating these individual whole-frame pictures, than it is at doing the
    same for pixel-level movements at such a large size - if you see what I mean
    .... Maybe, it's something to do with the different colour and monochrome
    resolutions of the eye. Now that I'm thinking about this a bit more, perhaps
    it's a combination of the speed of the movement, AND the size of the screen
    AND how close you are sitting. Perhaps there are combinations that show the
    problem worse. Next time I go to this same cinema, I'll try sitting in a
    different place, and maybe taking my glasses as well, just to see if it
    makes any difference to place some optics in front of the eye.

  17. Ron(UK)

    Ron(UK) Guest

  18. b

    b Guest

    I hear what you're saying Arfa. bit do the displays you mention really
    consume less power'? In the case of the plasma sets in particular
    you'd have to go back to the early 70s valve colour tvs to find
    anything approaching their wattage consumption! so much for progress
    and ecology. instead of ranting on about not leaving sets on standby,
    they should bring in laws against this modern [email protected]!

    I think at least in the Uk, what has been done to broadcasting is a
    disgrace. Sell everyone flat screens with awful artefacts especially
    on tv reception, then use that as an excuse to phase out analogue and
    also prepare the ground to sell HDTV.
  19. Arfa Daily

    Arfa Daily Guest

    Yes, you're right, the plasmas, at least, do consume a lot of power. I don't
    think that the LCDs are too bad - I haven't really looked to be honest, but
    I seemed to think that low power consumption was a 'selling point', although
    this could be just sales hype; I suppose it depends what you're comparing it
    to. I agree with what you say about broadcasting in the UK, although I think
    that the whole situation is a lot more political than just phasing out
    analogue in preparation for HD. The government stands to make billions
    selling off spectrum space to rich users like cellphone companies, just as
    soon as they can drive all the existing users off. 470 to 860 megs give or
    take a bit of 70cms amateur space and a few other users between bands IV and
    V, is an awful lot of spectrum to be able to put up for auction, if you can
    make the new users co-exist with the originals by making it all digital ...

    We are heading back for the old days of band III TV in terms of ironwork on
    the roof now. We had got it down to nice neat little 10 ele yagis for the
    most part. Now, in order to receive the crap digital signals - which let's
    remember are, according to Monkey on the TV adverts, going to be dead easy
    to receive just by plugging into a set top box - you need a 650 element
    triple reverse co-phased crossed dipole anti-ghost log periodic about 6 foot
    long and with a bloody great cake-cooling rack on the back ! Cost to install
    ? Oh, only about 180 quid ...

    And let's not forget, as most people seem to have, or have not really
    understood in the first place, every little portable in the kitchen,
    conservatory, kids bedroom, garden shed, and every VCR, analogue DVDR, PVR
    etc, is going to need yet another 30 quid STB ...

  20. N Cook

    N Cook Guest

    The driving force is the sell off of much of the then released UHF
    "airspace" - talk of intangibles, how many billions was that "commodity"
    sold for ?.
    So people can drive their cars watching films via the extra bandwidth to
    their mobile phones - brilliant.
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