DIY Light Table

Discussion in 'Darkroom Equipment' started by donbga, Nov 28, 2004.

  1. donbga

    donbga Member

    Messages:
    2,084
    Joined:
    Nov 7, 2003
    Shooter:
    Large Format Pan
    I'm not sure if this is the best forum to post this question but does anyone know of any sources for building a light box roughly 3x4 feet in dimension?

    Don Bryant
     
  2. Jorge

    Jorge Inactive

    Messages:
    4,532
    Joined:
    Sep 6, 2002
    Shooter:
    Large Format
    "Build your own home darkroom" by Lista Duren and Billy McDonald.

    They have a diagram for a 2x3 box, but I dont see why you cannot adjust the size to fit your needs.
     
  3. glbeas

    glbeas Member

    Messages:
    3,307
    Joined:
    Sep 25, 2002
    Location:
    Roswell, Ga.
    Shooter:
    Multi Format
    Light boxes, or light tables as graphic art folks call them are easy to build. Easiest one I ever built was onto a folding table. I built a box on top with 1x12s and used trim to make a ledge around the inside deep enough for a sheet of glass and a sheet of translucent plexi stacked. A couple of twin bulb flourescent fixtures are laid on thier backs inside wired together to an external switch. If the glass is very large a support rod should be put in the center, a threaded rod with nuts and flat washers in a hole on the table and the other end with a rubber tip capping it and adjusted to be level with the trim ledge. The inside may be painted white to even the illumination. Some folks even build a door into the side of the box to make it easy to change the bulbs out.
    It's not much different from a uv contact print box.
     
  4. donbga

    donbga Member

    Messages:
    2,084
    Joined:
    Nov 7, 2003
    Shooter:
    Large Format Pan
    A thicker sheet of plate would be better, the shadow of the rod would be totally unacceptable.

    I'm not sure I see the utility in that. It would be easy enough to drop the support out.

    I would say not at all like a UV printer, but thanks for the suggestions.

    Don
     
  5. rbarker

    rbarker Member

    Messages:
    2,222
    Joined:
    Oct 31, 2004
    Location:
    Rio Rancho,
    Shooter:
    Multi Format
    I guess my questions, Don, which I haven't seen addressed yet, are color temp, optimal spacing for evenness of illumination, and ideal level of illumination (how bright should it be?).

    If it's to be used strictly for B&W, color temp isn't much of an issue. But, for color transparencies, it would be. I'm not sure if "daylight" bulbs provide the proper color temp, or if specialized bulbs are needed, for example.
     
  6. Jorge

    Jorge Inactive

    Messages:
    4,532
    Joined:
    Sep 6, 2002
    Shooter:
    Large Format
    Note, that with the new fluorescent bulbs with integrated ballast all you have to do is rig a box with sockets and just screw in a few bulbs, far easier than wiring for ballast and conectors.
     
  7. kwmullet

    kwmullet Subscriber

    Messages:
    889
    Joined:
    Jan 3, 2004
    Location:
    Denton, TX,
    Shooter:
    Multi Format
    What would be a good alternative to florescent bulbs? At some point (since, as are probably many of you, I'm always designing my next darkroom in my head) I want to have a light table recessed into a counter of my darkroom. Florescent bulbs would be a no-go, since they continue to fluoresce for a time after the power is removed presenting a danger of film/paper fogging.

    How practical would it be to put a bunch of white LEDs wired in sequence as a light source? Are LEDs expensive?

    Also, what's a good way to make a sheet of plexi evenly translucent? Sand it? Unless you own a good spray painter, I would think painting would be unevenly thick, show brush strokes and tend to yellow over time. Also sounds unnecessarily thick.

    -KwM-
     
  8. wdemere

    wdemere Member

    Messages:
    85
    Joined:
    May 11, 2004
    Shooter:
    35mm

    These guys may be able to help: http://www.discreteled.com/

    They have a flashlight bulb that is all red that might be a handy darkroom tool too.

    Good luck,

    William
     
  9. kwmullet

    kwmullet Subscriber

    Messages:
    889
    Joined:
    Jan 3, 2004
    Location:
    Denton, TX,
    Shooter:
    Multi Format
    William,

    Thanks for the tip. I wouldn't need or want the light table to be safe when on, though. I'd only use it when I was "light". I just want it to give me a good even white light table surface, and when I turn it off and go dark to be sure it doesn't fog paper or film like florescent tubes might.

    -KwM-
     
  10. Craig

    Craig Subscriber

    Messages:
    784
    Joined:
    Apr 8, 2004
    Location:
    Calgary
    Shooter:
    Multi Format
    I built a light table for a geologist friend to sperad his maps on, it was 3x5' and I used a piece of 3/8" sandblasted glass. Its strong, self supporting and when sandblasted quite uniform illumination. I put flurescent lights underneath, and had the top hinged to allow access for changing the bulbs. I can't recall the cost of the glass, but I went to a commercial glass shop and it wasn't that expensive.
     
  11. Laurent

    Laurent Subscriber

    Messages:
    1,269
    Joined:
    Oct 15, 2004
    Location:
    France
    Shooter:
    Multi Format
    A friend of mine made one for me. He was making neon signs and just used some used ones to make the thing. It works fine, costed nothing...

    It may be a gold mine for DIY if there's such a company near your home, they usually have tons of used signs, and the box itself makes a very neat table, even if you have to fix the tubes and change the panel.
     
  12. donbga

    donbga Member

    Messages:
    2,084
    Joined:
    Nov 7, 2003
    Shooter:
    Large Format Pan
    Craig,

    Excelent suggestions, 3/8" glass should be plenty strong.

    Thanks,

    Don Bryant
     
  13. David Ruby

    David Ruby Member

    Messages:
    203
    Joined:
    Sep 17, 2003
    Location:
    Boise, Idaho
    Shooter:
    Multi Format
    LED are quite expensive still, and very point source. You could use them, but you'd really have to make sure the glass could diffuse the light well enough for you.
     
  14. argentic

    argentic Member

    Messages:
    1,722
    Joined:
    Sep 7, 2002
    Location:
    Echandelys,
    Shooter:
    4x5 Format
    Just a hint. Sometime ago I bought a viewing table for X-Rays very cheap ($ 30). It turns out to be the best light box I have ever had, with very even lighting by four 6000 K tubes. I would have never been able to make such a quality lightbox for so little money myself. I think in the medical business they are called "negatoscopes".
     
  15. Shesh

    Shesh Member

    Messages:
    161
    Joined:
    Nov 27, 2002
    Location:
    Massachusett
    Shooter:
    Multi Format
    Don,

    I built a light table for myself and here are the details: The surface dimentions of the light table are 20"x48". The depth of the box containing the tubes is just short of 7" and the tubes are located along the base. The 2 tubes are placed at approximately 1/3rd and 2/3rds positions. Before you finalize the positions of the tubes, place the glass and acrylic on the light table, switch off all the surrounding lights to make sure you do not see any dark patches. reposition the tubes until you are satisfied.

    By far the most expensive components of the light table are the acrylic and glass sheets. Before you decide on the final dimentions, ensure that tubes with the right color temperature are available in that size.

    a. 2x4's = 30" x 4 nos. (legs)
    b. 1x6's = 48" x 2 nos. (border between legs and light box)
    c. 1x6's = 20" x 2 nos. (border between legs and light box)
    d. Wheels x 4 (To help move the table around - This thing gets heavy after the glass and acrylic sheets are added)
    e. particle board (3/4") = 48" x 20" x 1 nos. (base of light box)
    f. particle board (3/4") = 7" x 48" x 2 nos. (sides of light box)
    g. particle board (3/4") = 7" x 21.5" x 2 nos. (sides of light box)
    h. 1/4" Glass = 49.5" x 21.5"x 1 nos. (top of light box)
    i. 1/8" White Acrylic sheet = 49.5" x 21.5" x 1 nos. (for diffusing the light)
    j. "L" shaped Border to hold the sheet down to the table slightly larger than the dimentions of the table with one of the sides of the "L" being atleast 3/4", preferably 1"
    k. Fluorescent light fixtures x 2 nos.
    l. Fluorescent tubes - 5000K, 90 CPI x 2 nos.
    m. Wiring x 15 feet (with ground).
    n. Gloss or semi-gloss white paint for the inside of the box.
    o. Paint for the outside of the box.
    p. Aluminium foil (slightly crumpled) to line the inside of the box to add reflectance.

    Tools:
    1. Hacksaw.
    2. Drill Gun and bits.
    3. Screw driver.
    4. Pencil.
    5. Ruler.
    6. Spirit level.
    7. Sand paper.
     
  16. donbga

    donbga Member

    Messages:
    2,084
    Joined:
    Nov 7, 2003
    Shooter:
    Large Format Pan
    I would prefer never to use particle board as it is unnecessarily heavy. And I have no limit on tools, so it's not an issue for me. Cutting wood with a hacksaw seems to rather difficult at best. Poplar or white pine would be my choice for wood for the side panels. 3/8 inch plywood for the base will be plenty rigid. I think that at least 4 tubes would be desirable. I'm not sure that the aluminum foil adds anything, rather a paint with a high albedo would work fine. Thanks for the suggestions.

    Don


    Don
     
  17. donbga

    donbga Member

    Messages:
    2,084
    Joined:
    Nov 7, 2003
    Shooter:
    Large Format Pan
    Excellent suggestion!!

    Don
     
  18. David Ruby

    David Ruby Member

    Messages:
    203
    Joined:
    Sep 17, 2003
    Location:
    Boise, Idaho
    Shooter:
    Multi Format
    I just had an idea. In my dry area, the countertop has a location on my side (the wife has her own side of course) with a knee space below. I think this would be a great location to build in a light box from below. The glass would be flush with the surrounding counter. I'll have to add this to my to-do list!
     
  19. yeahyeah

    yeahyeah Member

    Messages:
    4
    Joined:
    Nov 29, 2003
    Keep it simple.

    The xray viewer sounds like a great idea. Simple & inexpensive.

    I still use the light box that my dad made for himself around 1940 when he was a teenager. 'Big Red' is VERY simply constructed and works perfectly well.
     
  20. Shesh

    Shesh Member

    Messages:
    161
    Joined:
    Nov 27, 2002
    Location:
    Massachusett
    Shooter:
    Multi Format
    There were 3 problems I encountered when I considered the x-ray viewers available via glass shops -
    1. Could not find one 48" long.
    2. The ones that used glass imparted a distinct dull muddy color and did not diffuse the light enough.
    3. The ones which used acrylic used a very thin layer of acrylic (and hence could not support my bending over the box and viewing the film with the loupe.

    I guess, if these problems can be avoided, x-ray viewers would be the way to go.
     
  21. argentic

    argentic Member

    Messages:
    1,722
    Joined:
    Sep 7, 2002
    Location:
    Echandelys,
    Shooter:
    4x5 Format
    I don't bend over my X-Ray lightbox. But if you want to, a sheet of glass on top of the acrylic should solve the problem. Mine is about 48" long. So they do exist. I guess even longer ones exist.