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Question for B4, Alan Roser and other tech's

Discussion in 'Projectors, Screens & Video Processors' started by Gordon @ Convergent AV, Jun 17, 2001.

  1. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    There's some debate about screen size v light ouput from projectors going on here and there's another thread where someone is asking about HD6 lenses.

    So, here's something that interests me. Presumably the lenses used in projectors are designed to focus at an optimum distance for best sharpness. Are there lenses which are also designed to have best focus at the edge with 16:9 rather than 4:3 shaped images?

    If so, can you let us know which lenses are designed for what application and ideal focal lengths (if that's the correct term) for the lenses used in some of your Seleco's and the Barco's B4 is familier with.

    Gordon
     
  2. Roland @ B4

    Roland @ B4
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    Gordon
    The HD6 lens is a hybrid lens. It was designed for use on 6" and 7" CRTs.

    There are basically only three types of lenses manufactured for CRT the vast majortity made by USPL in America

    There are the TAC series which are all acrilic good for light output poor resoloution typically 5 lines per mm.

    The HD series 6,8,145 etc Which are hybrid lenses( Part acrilic part glass ) these have good alround performance for resolution and light output. typically 10 lines per mm.

    There were also some special lenses made in the past that were all glass, excelent resolotion but ate up the light.

    A modern 7" CRT projector with TAC lenses should produce 1200 lumens
    HD lenses about 1000 lumens
    All glass about 600 lumens

    TAC lenses had a throw of about 1.2 to 1
    HD about 1.4 to 1

    CRT's with very few special exceptions are only produced in a 4x3 format so the lenses were designed to match. As regards better lenses for 16x9 as you are only using the centre portion of the phoshper edge focus will be better in 16x9 anyway.


    Happy to tell which lens was fitted to what but there are so many variations would have to do it on a case by case. Hope to publish a list soon.

    Hope that helps :)
     
  3. Roland @ B4

    Roland @ B4
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    HD 145 is the newer version it has better contrast and focus. The coatings are much finer.

    It is availale in a colour filtered form on the Cine 7 for better reds and greens
     
  4. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    B4:

    This is great, always learning!

    Excellent thanks but it raises some more questions.

    If HD6 and HD145 are both from the same range, of the same resolution and same throw distance....why would you use one rather than the other. Is it to do with colour accuracy or something else.

    Also, are you saying that all these lenses are able to achieve the same degree of focus throughout their operating range.

    Gordon

    P.S. Can you e-mail me please so I can contact you direct about a matter...thanks.

    [ 18-06-2001: Message edited by: Gordon, StereoStereo ]
     
  5. tryingtimes

    tryingtimes
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    Is this correct? I thought that you would be using all of the phosphor but only the centre of the lens! I suppose the increase in sharpness should still be present because the centre of the lens will distort the path of the phosphors less. Is this right?

    Alex
     
  6. Roland @ B4

    Roland @ B4
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    Alex
    Perhaps I could have worded it better.

    When an anamorphic image (ie 16x9) is displayed on a CRT the vertical height is crushed. You still end up with the same number of scan lines they are just closer together.

    The image is reduced in hieght from the top and bottom. so what was the center of the 4x3 image is also the centre of the 16x9. The width sould stay the same.

    This then means that you are not using the very top and bottom coners of the lens where optical distortion will be worst.
     
  7. Nic Rhodes

    Nic Rhodes
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    Bump.

    Sorry to trawl up an old subject. Can anyone explain about the following other lenses.

    HD 10, TOC-7, HD 144, HD 134, HD 8, HD 300, HACC

    I am particularly interested in finding more about HD 10 and HD 145 (already covered).

    Does anyone know a source of this info?
     

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