how far can you take a slide projector?

Discussion in '35mm Cameras and Accessories' started by sherwin, Aug 16, 2010.

  1. sherwin

    sherwin Member

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    Hi there,

    So i am considering possibilities for an arts project involving outdoor projection. The projection surfaces are the sides of a large concrete building. I will project from distances varying from 10 to 30m. Budgetary concerns and a preference for film grain over pixels, has led me to considering slide projectors.

    These are my concerns:

    1. From what i understand, at 30 metres, 500w 35mm slide projectors won't cut it. Will larger format slide projectors such as the Beseler Slide King give me a rich image from such a distance (minimal ambient light)?

    2. I want the projection to be as big as possible but many of the projectors I come across come with 70mm or longer lenses. Are wide angle lenses a rare commodity?

    I live in Australia so there seems to be less of this stuff on ebay compared to the states. Any local tips would be much, much appreciated.

    Cheers,
    Sherwin
     
  2. Leigh Youdale

    Leigh Youdale Member

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    Not sure how helpful this is but I seem to recall that the light from a projector falls off at a rate equal to the inverse of the square of the distance. In other words it's not a linear reduction.
    So a projector optimised for use in a room at (say) 5m distance is going to look pretty dim even at 10m and probably hardly viewable at 30m. Maybe check that out first.
    Second is that boosting the light output is problematic because the heat will likely destroy the transparency, if not the projector. Standard cooling fans might not cut it.
    The longer lenses you're noting were made so that conventional 35mm slide projectors could fill a standard screen in a larger hall or venue. There were also zoom lenses made.
    I think you'd suffer less frustration by hiring a powerful digital projector from a specialist audio visual supplier. Kayell might be a useful point of enquiry.
    I don't think the subtlety of film grain is going to be apparent when projected on the side of a large concrete building!
     
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  3. sherwin

    sherwin Member

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    Thanks Leigh. Digital projection is probably the way to go and if it weren't for the significant cost difference I probably wouldn't be considering analog. This project is set to screen every night for 22 nights so the costs add up!

    I may be able to rig the slide projectors so that they are 10-15m from the screen. This makes a wide angle lens imperative. I was wondering if anyone could name a few lenses (that I might be able to find on ebay) or any 35mm or medium format projectors which come with a wide-ish standard lens.

    Cheers
     
  4. Greg Davis

    Greg Davis Member

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    When I was in college, some of the classrooms used a slide projector that was 30 meters away, roughly. I don't know what kind they used, but they do exist.
     
  5. Steve Smith

    Steve Smith Subscriber

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    For the size you want to magnify the images to, I don't think a digital projector will be bright enough. They are only just bright enough at 'normal' projection sizes.


    Steve.
     
  6. Lee L

    Lee L Member

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    It's really more a matter of how large your projected image is rather than distance. You're concentrating the illuminating passing through the slide over a given area. With a wide lens at a short distance covering the same screen area as a long lens at a large distance, the image will be approximately the same brightness. Both digital and slide projectors have a wide enough range of brightness that you'd have to be specific about models to get any relative brightness information, and you'd also need to be specific about the ambient light levels you're trying to overcome.

    Projector lenses vary widely in quality, from plastic zooms (and zooms are typically slower than fixed focal lengths) to great fixed length fast lenses with excellent glass. If image quality is a concern, you'd need to factor that in. Schneider, Zeiss, Leitz, Buhl (in the US), among others make excellent slide projector lenses. Wide angle slide projector lenses are rare. Usually a 90mm or longer lens works for the majority of common slide projection setups. Also, with a short lens, you'll need to have the projector closer and tilt it more to cover the same area, leading to 'keystoning' in the projected image, i.e. the bottom of the image will be narrower than the top, and the sides will fan out going from bottom to top.

    Lee
     
  7. David Brown

    David Brown Subscriber

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    Lots of variables here, but what you are talking about is a "long throw" projector with appropriate lens. Such things do (did) exist. 35mm projectors were routinely used in auditoriums for distances over 30 meters. Sorry, I do not have any suggestions for sources; but if it were me, I'd start with the AV guys at a local university.
     
  8. sherwin

    sherwin Member

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    Thanks everyone.

    Based on your feedback, I'm going to dig around for some long throw projectors (did i mention that I need more than just one!). I don't hold out much hope but to maximise my chances, what kind of variables am i looking for to indicate that a projector is 'long throw'? So far i've only been looking for a high watt lamp and a fast lens. Anything else?

    Thanks again
     
  9. holmburgers

    holmburgers Member

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    When has a digital projector ever looked brighter or better than an analog projection? IMHO, never. Not to mention, once you find the suitable analog projector, you could probably buy two and do a stereo slide show before you could afford one digital projector. But I digress....

    There are always some long throw lenses on eBay, specifically I remember seeing some Buhl ones. I'm sure they're now selling for a fraction of what they cost new. I'm sure resources abound with regards to high-power projectors, etc. Make sure you have backup slides and an excellent cooling system.

    Long throw simply equals long focal length I believe.
     
  10. David Brown

    David Brown Subscriber

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    Well, yes and no. As for the lens, think of telephotos. But the light source matters for true distance projection, also (as mentioned). You might even have to mount the slides in glass.

    Something like an Elmo or this:

    http://cgi.ebay.com/Kodak-Ektapro-9020-slide-projector-nice-/360288885982?pt=LH_DefaultDomain_0
    Note the 300W lamp!!

    Here's one in Oz - http://cgi.ebay.com/KODAK-EKTAPRO-5...0455246688?pt=AU_Cameras_Projection_Equipment

    In the Kodaks, at least an Ektagraphic, not a Carousel made for home use.
     
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  11. Sirius Glass

    Sirius Glass Subscriber

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    What he said. Get a long lens.

    Steve
     
  12. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    Most modern outdoor projection equipment is, of course, digital. This would be a rather pricey rental item, try A/V rental firms.

    You might be able to get by with an auditorium projector: if you only need it for a short time, and can put an educational/arty-farty slant to your usage, you may be able to borrow a few from a local university. Also try A/V firms, a big one might have some available for not that much money. These things normally take 3x4" (whatever the standard size) glass mounted slides. Using these with color transparency materials may be problematic as the light intensity in these things is fierce. Color ink-jet on mylar film might work.

    Your second problem is 'the side of a concrete building'. You will need an outdoor projection screen, trying to project on concrete isn't going to work very well. Outdoor screens can be rented. You can make one from Tyvek and screen paint, or you can paint the side of the building with either screen paint or the best white titanium paint you can find.
     
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  13. sherwin

    sherwin Member

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    Thanks Nicholas but unfortunately, a screen is not an option as i'm projecting onto the walls of a high building.

    Your note about protecting the slide is also a main concern - I plan to leave the projectors on all night (or at least for 4-5 hours straight). Do you think ink-jet on mylar film will be able to cut it?
     
  14. Ektagraphic

    Ektagraphic Member

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    You could get an extra bright lamp modual for an Ektagraphic or even one of those very, very high power xenon units put out by NOVA as far as I know. Plus the proper lens. You'd be all set.
     
  15. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    I have a Beseler Slide King, and they do project a beautiful image, though I haven't tried projecting on a surface as large as the side of the building. The one I have was used in an auditorium. There are wider lenses, but they're hard to find. I've picked up a lens or two and some slide carriers from a place that specialized in them. The projectors are usually fairly cheap on eBay, but the accessories can be a little pricey in comparison.


    Bear in mind that you may have to make custom mounts for your slides with a Slide King, since carriers for standard sized mounts can be hard to find, but once you've narrowed down the images in your show, it's not so hard. You can cut them from mat board like little window mattes.

    It is also a totally manual projector like in old movies--insert slide, move carrier, remove old slide, insert new slide, and then move the carrier back to the previous position.
     
  16. E76

    E76 Member

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    There are many specialty projectors made for exactly these types of applications, but even they are only so bright. Typically, when very high brightness is required, multiple projectors are stacked, each projecting the exact same image on to the same screen, with the optics adjusted to bring the images into register. I'm not sure if this is possible with ordinary slide projectors, as you need to be able to shift the lenses.
     
  17. 68degrees

    68degrees Member

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    If the Slide King cant do it I dont know what can. They dont call it the Slide King for nothing. That thing comes in a metal box that looks like a rocket launcher case.
     
  18. munz6869

    munz6869 Subscriber

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    For your interest, the throw in my little venue at work here is 15.5 metres from projection room to screen, and our fancy new HD projector needed a lens upgrade for that. At 6000 lumens, and with the longer focal length, it projects a 2.5m x 4.44m (16:9) picture really brightly. The 16mm Kinoton here has a 45mm f/2 lens for the same throw with a 1.2kW lamp, and is also very bright.

    It has been interesting looking at some of the fancy new projector installations in lecture theatres here - one I looked at yesterday had a 4 lamp DLP projector installed (ceiling mounted, really close to the screen), just to compete with the GIANT west-facing window running the length of one side of the space. Technology battles architecture...

    new lecture theatre.JPG

    Marc!
     
  19. polyglot

    polyglot Member

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    Distance is irrelevant, it's magnification that matters for power/brightness, i.e. image size. For the side of a building and decent brightness, you need a thousand watts or three. You get the same effect from a short lens up close as a long lens further away as long as their relative aperture is the same.

    As choosing the focal length, it's a function of your slide size and how far away you want the projector. Same geometry as with a camera.

    There are occasional events where people project patterns on whole buildings and that particular one is done 5kW lamps shining through 5" mylar rolls that advance every two minutes; I think the image is around the 5x7" size. They're 4-story-high images though and projected onto dull sandstone - if your building is white or concrete, you will get better brightness.

    I would suggest you look at getting something at least as grunty as a Goetschmann G67 (it's like a Slide King but more modern; takes the 85mm mounts). 35mm WILL NOT cut it because the optical flux through the slide required to light up a building will melt it. If you wanted to hack a Slide King or similar for wide angle, you could start by mounting shorter RB or RZ lenses to the front.

    Of course you can get a digital projector to do it, but you're talking about a cinema-class Barco for many tens of $k, not a powerpoint-thrower designed for office use.
     
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