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CRT Lens question

Discussion in 'Projectors, Screens & Video Processors' started by Mr Cinema, Oct 9, 2004.

  1. Mr Cinema

    Mr Cinema
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    Now this might be a really dumb question, but here goes.

    I recently got hold of a Seleco SDG 700 to replace my ailing Barco 701s.
    (It worked out cheaper than replacing all three tubes)

    However, I've ended up with a smaller picture because of my limited throw (12Ft) Now I know I should have checked etc etc. But my question is are the HD145 lenses on the Seleco going to be the same focal length as the HD145
    lenses on the Barco? If they are different would changing them bring my picture back up to its original size?

    Thirdly would it be a sensible thing to do or am I entering a world of pain?

    Any help sincerely appreciated.
     
  2. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    This is one for Roland I suspect. However I woudl expect the HD145 lenses to be the same focal length on both. Perhaps the difference is down to the electronics in the projectors and how much phosphor they each actually used when displaying an image.

    Are you running the new SDG at same rate you ran 701? I am unware if the SDG does this but many projectors limit the amount of phosphor they use as you up the resolution and refresh rate of the signal you send to them. This is due to limitations of their electronics not being able to scan all the way across the face of the tube then get back to start next line in time...so they make the width less.

    Might be worth trying lower signal resolution to start.

    Just an idea anyway. No doubt Roland or Chris will be here soon.....

    Gordon
     
  3. Mr Cinema

    Mr Cinema
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    Thanks Gordon. The image is actually filling all the available width on the face of the tube. Bags of height left though. Perhaps I could turn it on its side :)

    I was under the impression that the Seleco had slightly bigger tubes than the 701s, so if the lenses were the same focal length then wouldn't more tube mean a wider picture at the same thow? I'm obviously wrong but can't work out how.

    I'm using and Isacan pro from a Denon 2800II to feed the Pj which doesn't have the ability to change res as far as I know.

    Nice picture though, if only it was a little bigger!
     
  4. JMPremier

    JMPremier
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    The lenses should be the same as gordon says.
    The difference will be the distance from the phosphor to the lens.
    Just think of a magnifying glass, you only need to move it a very small distance from the subject for the magnification to change.

    John
     
  5. Mr Cinema

    Mr Cinema
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    Thanks John. Makes perfect sense.

    Arse! No getting round this one then.
     
  6. JMPremier

    JMPremier
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    Are there no spacers that you can add or remove?
    Maybe roland may have something that would fit?

    John
     
  7. Mr Cinema

    Mr Cinema
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    Will look into that. There is a bag of spacers for schlimmphunthingymcwhatist adjustment. It's a question of which way to go. Presumably closer to the tubes?? And would the teeny amount of distance we are talking make that much difference?

    Good Idea though. Thanks!
     

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