Lengthening the lens throw

Discussion in 'Projectors, Screens & Video Processors' started by md2, Jun 17, 2002.

  1. md2

    md2
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    I have a problem in that I want to move my AE100 projector further away from the screen, but the resulting image size is way too large. Ideally, I'd like to almost double the length of the lens throw.

    Does anyone know of any filter or attachment which could be used on a projector, to achieve this?

    ...there must be a solution.
     
  2. tonyoevans

    tonyoevans
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    I had the same problem in that I needed to move the projector back as I could not mount it to the ceiling (loads of reasons)

    So I did a little experimenting, I figured that if you took a X2 camcorder lens and projected through it (the opposite way it is designed to work) the it should reduce the image by 2.

    I went to tottenham court Rd and got a cheap one to test my theory and it worked. However as the diameter of the lens was a little too small the image was slightly distorted at the edges and the image was slightly cut in the top corners.

    However the principle seems quite sound, and I mentioned this to panasonic but they have no adapter or plans of producing one :(

    In the end after looking for a suitable lens I decided to just move my projector back and get a larger screen, and I'm happy that I did :D

    Tony
     
  3. md2

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    That's interesting. Was the camcorder X2 lens the largest one you could find? If it was possible to source a larger one, this sounds like the perfect solution.
     
  4. tonyoevans

    tonyoevans
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    I looked around for ages. I was basically looking to spend no more than £35 and I eventually found one. It seems that most of these lenses are for older style camcorders, the ones which have a very large diameter lens and as such they seem few and far between.

    I was specifically looking around for a X2 converter as this gave me the perfect viewing size, so I am unsure what you can get. My initial thought is that if the lens went above X2 it would probably be a manual telephoto lens.

    If you look hard enough through second hand camera shops you maybe lucky. You can buy new lenses from many manufacturers but the cost is around £100 so unless you manage to find the perfect one it's probably not worth the risk.

    I will get the details of the lens I bought and will list them here so you can get and idea of what you should be looking for. :)
     
  5. md2

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    thanks. That would be v. useful.
     
  6. RichardH

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    My experience of 2x converters etc (for 35mm cameras rather than camcorders) is that they decrease the brightness - is this a problem for the PJ, too?
     
  7. tonyoevans

    tonyoevans
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    There was a very very slight decrease in brightness but not really that noticable
     
  8. Ian Oliver

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    Yes you right there third party lenes available for most poular projectors. However, they are usually very expensive, normally in excess of £1000. Post or email details to [email protected] and I will arrange a price for you

    Ian
     
  9. Chris Frost

    Chris Frost
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    Ian,
    Just some friendly advice...This forum welcomes contributions from AV professionals, but it is the done thing to put your company details in your signature (but not hyperlinks as this constitutes free advertising).

    You can get the rest of this sites T's&C's from the sticky threads at the top of each forum page.

    Nice to have you onboard.:)

    Regards
     
  10. md2

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    Thanks Ian, but £1000 is far more than I'm prepared to pay. After all, all it requires is a couple of lenses housed in a little tube of plastic. After all, we're not talking about photographic quality optics here - at least not for the AE100.

    Tonyoevans - you mentioned that you'd provide the details of the X2 converter you found. That would be really useful...
     
  11. nwgarratt

    nwgarratt
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    Does anyone know where to get one of these x2 camcorder lens for a PTAE100?
     
  12. NonPayingMember

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    Tonyoevans what size screen did you try the x2 lens on? I would worry that the AE100s 700ANSI (iirc) throwing a longer distance and through an additional lens would result in a more noticeable drop in brightness (and colour strength) if the screen size was large.
     
  13. tonyoevans

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    Sorry guys I dont check my yahoo email account that often so have just seen your posts.

    I ended up not using the lens as it caused the image to be cut-off slightly at the corners as well as some curving of the image.

    In the end I just got a bigger screen!

    I havent got details of the lens but will take a look to see if I can find it.
     
  14. Piper64

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    In 2004 I wanted to move my projector (Infocus X1) a couple of metres further back from the screen, to the other side of a partition panel, so I could hide it behind a small glass window. Our home is 400 years old and the projector just didn't look right stuck in the middle of the ceiling of our front room. Placing it behind the small glass window would also exclude unwanted fan noise. I quickly realised that moving the projector behind the panel, 6.3m from the sceen, would cause the image to be much wider than the 1.8m screen. We couldn't have a larger screen because it already covered part of the fireplace.

    Like tonyoevans above I figured that a teleconverter should reduce the image size. The first one I tried worked exactly as I wanted in reducing the image size but the aperture wasn't wide enough to cover the beam coming out of the projector. I then sourced a Raynox DCR 1850PRO 1.85x converter from Jessops - about £140 at the time. This was a bit of a gamble but they said they would take it back if it didn't do what I wanted.

    It worked perfectly with no image distortion; giving me a throw ratio of 3.5 with some further zoom adjustment. I had to improvise a way of supporting the lens off-axis so that it could cover the whole beam (remember that with a ceiling mounted projector the beam is offset downwards). I had a home-made ceiling projector mount to save height (two pieces of mdf with carefully placed holes and connected by three bolts with wing nuts allowing plenty of adjustment). Two pieces of small (jack?) chain attached to the lower piece of mdf supported the front of the converter lens at the optimal angle. The back of the converter lens rested on the rim of the projector's lens, after removing a plastic focusing ring from the front of it (a bit scary). To further reduce the impact of the "cinema", a clever carpenter managed to hide the pull down screen in a hollowed out piece of reclaimed oak, which luckily looks very like the existing beams.

    In August 2011 I upgraded to a BenQ W1100 projector, and reused the Raynox lens. This time I didn't have to remove anything from the front of the BenQ's own lens.

    A quick search of this forum for "throw ratio" did reveal a projector that could provide this level of ratio, but it costs over £10,000. Jessops no longer sell the Raynox lens but it is still available via eBay and Amazon. The Panasonic Teleconverter Lens For DMC-FZ30 (DMW-LT55E, 1.7x) looks like it might be wide enough but I couldn't see a thread spec.

    This is a long long time since the last post here, but if new enthusiasts are hitting the same problem I had, I hope they may find the above useful.
     

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