Replacing slide projector bulb -- is an LED light an option?

Discussion in 'Film and Processing' started by farkle-mpls, Apr 2, 2016.

  1. Hello. I just ordered a replacement 300W incandescent light bulb for my Kodak carousel slide projector but the process did get me
    thinking ... those bulbs are hot and for (especially) Kodachrome slides there was always the concern about the heat of prolonged
    projection causing the color dyes to fade.

    I realize that color temperature would be a concern but has anyone found a "cooler" (less heat) option for projector bulbs? I'd love it if I
    could get an LED bulb but I've searched Google and Amazon without any luck. I did see some halogen options. Does halogen burn
    cooler (less heat)?

    Thoughts? Ideas?
  2. I thought the same thing after I replaced an enlarger bulb with an LED bulb that had the same color spectrum. I though doubt though that manufactures would make them in prongs with the wattage and reflective ability to use in a film projector. It though would be nice.
  3. I don't think there are any LEDs that could come anywhere near the brightness of conventional incandescent or halogen
  4. SCL


    Halogens aren't cooler, they're usually quite hot.
  5. Most modern design projector bulbs with built
    in reflectors are halogen. Halogen is hot.

    Projector optical systems are designed to
    work with a specific bulb and even a specific
    filament within the bulb shape. So an led
    replacement would have to be designed
    specifically to be an exact replacement. Even
    then not sure if it could match the filament.
    Not enough demand to justify the r&d.
  6. The Kodak projector lamps that I know of, such as ELH, have a dichroic reflector. The reflector does not reflect IR, so the actual heat (IR) hitting the film is not so high.
    I believe that there is also an IR absorbing glass filter, too.
    It would be difficult to build your own LED adapter, and the demand is likely too low for a commercial version.
    While I do like the old technology, a better modern way is to scan them and view them on an LCD television screen. Nice big and bright.
  7. [Les] " Also form factor is another obstacle when trying to convert incandescents to LEDs."

    Yes, there's the problem. The optical system in a typical projector needs all the light energy to come from a small area;
    the condenser(s) or reflector has to get as much light as possible through the projection lens. It's hard to do that from a larger, less intense source. Although LEDs are sometimes used in enlargers, they don't have to work that efficiently; in contrast a projector has to work in "real time" against ambient light. I would think it's possible to build a larger array of LEDs, all individually focused into the lens pupil, but I'm skeptical about a drop-in replacement lamp.
  8. Thanks everyone for the interesting (educational!) replies. Les, I like flashlight project! When I'm retired, I hope I have time for such projects as they'll keep my mind fresh and fingers engaged.
    Glen -- I do scan most of my slides but a friend of mine has hundreds of slides she inherited from her recently-deceased parents. She's never seen them (I looked -- they are well preserved Kodachromes from the 1960s and 1970s). I brought a spare projector and tray to her house, fired up the projector on LOW power and it ran for a couple minutes. Then the bulb fried. End of slide show before it began.
    In Minnesota, there is a "Batteries and Bulbs" franchise and they were able to order one for me. I also got another much cheaper off Amazon -- but I'm still waiting for both of them to show up.
    "No bulb, no show!"
  9. has basically every
    projector bulb there is and at reasonable

    Yes repeated projection can fade any slides
    not just Kodachrome. (Kodachrome is the
    most fade resistant of all slide film.) But that
    was more a concern for professionals who
    didn't want to ruin their originals. You can
    show your family slides all you want without
    any reason to worry.
  10. The right bulb is crucial! Many, many years ago, while still in graduate school, one of our projectors burned out its bulb during the weekly student-organized geology slide show. The department office had an entire box of replacement bulbs, so I picked one that looked alright. Installation went like a charm and we were back in business maybe five minutes later. Soon we noticed a faint smell, which was credited to the new bulb ("All new bulbs do that!"). A minute later the projector started to melt the slides and a few minutes later itself. Even now, twenty years latter, I am every once in a while reminded by my wife about "that new bulb smell".
  11. I bought a bag of 10 ELH bulbs from Goodwill, so when I get around to using the projector, I am not worried about bulbs.
    LEDs should be better at getting a lot of light from a small source than incandescents, but it would have to be designed right for a projector. I suspect that the appropriate number of LED chips would be mounted directly on a big enough copper block to get the heat out in the right direction.
    If you look at an LED, you will see that the actual chip is mounted on a copper block, and then a tiny wire goes from another lead wire to the top of the chip. There is special equipment to do that. Easy if you are making millions, hard for one.
  12. Another reason for using the old projector is as a replacement for scanning slides. I have over 5000 slides from my father, chronicling family vacations, holidays, fun and events. He was an excellent photographer with good composition, focus and lighting. He even made sure to get journalistic style photos -not stiff poses. So with a Kodak projector I can place the slides into the carousel, use my Canon 1DX camera and shoot directly into the projector with it's lens removed getting over 5000 x 3400 pixel images with less than 3 seconds per image. press project button, next slide loads, press shutter button, image captured. More resolution than that would be pointless, and I don't know of any scanner system that can operate that fast at that resolution. I can see each image as captured by "tethering" the camera to avoid huge errors in focus or exposure should they occur. I'll shoot in a fixed white balance setting in RAW files. using photomechanic I can quickly batch downsample and categorize images to upload to my website for roughly 1 MB screen images. Those that are interesting enough for special treatment, I can pull up the RAW file and spend time on it. By saving all the RAW files, this can be done for any of the slides and provides a good archive. (I have server with triple back-up.)
    I am looking for a much lower wattage bulb to lower risk the of burning up or fading the slides. I don't need to project onto a screen. Keep in mind the whole point of using the projector is for the fast load and consistent lighting while allowing for fast, high resolution image capture via DSLR. Making low resolution web copies of the files would take less than an hour for all 5000 slides using photo mechanic.
    If I find a lower watt bulb that works, and build a practical mount for camera and projector alignment, I'll post the results here. This has been done before (except the maybe not the low watt bulb) by a slide to digital service which if I recall correctly is in NY.
    ed_farmer likes this.
  13. Ray, how did you find the contrast of the images you captured, vs a "regular" scanner? Did you need to build some sort of rig to keep the camera and projector aligned? Do you have to do much (or any) post-prod on your captured images? Do you have any photos of your setup? I can't wait to get home and try this concept out - I have bunches of slides to "scan" and have not been enthusiastic about the process until now.
  14. "ray_riedel was last seen: Aug 14, 2016"

    - A two year old thread revived without much hope of the addressee replying.

    You don't need a lot of light for scanning, or rather camera copying. So it seems quite feasible to modify something like a Kodak Carousel with an LED lamp.

    There's still the issue of keeping focus between slides, holding the camera in position, and getting the camera to focus to lifesize, 2/3rds lifesize, or whatever.

    A purpose made front-of-lens or lens replacement slide copier attachment might be far more reliable.

    As far as matching the light output of a projector bulb with an LED: At present LEDs are about 6 times more efficient than a Halogen bulb, and you'd need a compact LED source of 50 watts or thereabouts to match the brightness. Still not yet economically viable I fear.
    Last edited: Aug 22, 2018
  15. The condenser lenses expect a certain shape for the light source.

    Certainly it is too late for slide projectors, to be economically feasible.

    I haven't followed digital projectors, though. The ones I know use the usual
    halogen bulbs. I believe that there are lower power projectors, for a much
    smaller image, that use LEDs.
  16. For the 1rst September 2018 the EU has forbidden all production of Halogen lights so the HLX lights in a projector (and enlarger) will be certainly much more expensive soon due to this new law. It will be now a special production light source.
  17. paul ron

    paul ron NYC

    EU stock up while you can for those old projectors.

    btw my mf projector has 1/4" heat glass and a filter of some sort, mirrored, between the light n slides.
  18. It's difficult to get details about the halogen lamp 'ban' from the sensationalist news articles, but as far as I can tell, it only applies to the stupid omnidirectional halogen 'pea-in-a-large-envelope' (no pun intended) style of bulb.

    I'm pretty sure that there are allowable exceptions written into the legislation. With the rider that I haven't yet had sight of any original documents!

    Having said that; such nonsense as an EU blanket ban on Borax and its products is just plain stupid, and shows an institutional poor level of technical understanding and of heeding even worse technical/chemical advice. The sooner we stop electing classics/social/political studies graduates to power the better. Let those useless entities go unemployed!
  19. I don't know EU, but the US allows all kinds of special use lamps, enough for people who really like incandescent lamps.

    Rough service lamps (for fans and other vibration sources) are allowed.

    I suspect appliance lamps used in ovens might stay around, too.

    Current US restrictions allow halogen replacements for ordinary incandescent lamps,
    but maybe not much longer.

    I suspect that the 10W lamps for safelights will stay around, for a while, too.
  20. "I suspect that the 10W lamps for safelights will stay around, for a while, too."

    - Ahh, now. Those could easily be replaced with a red or amber LED to advantage. Apart from being more efficient, the LED would be 'safer' too.

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