Light Box

The box is constructed of balsa wood, basswood, foamcore board, and four 12" threaded rods.  The frame consists of four wooden squares, three of basswood and one of balsa, shown lying horizontally at right.  The two bottommost and topmost squares are basswood, and the other is balsa.  The basswood is much stronger, so I used that to ensure rigidity where necessary, and used balsa for the rest.  There are screws and/or staples holding the square boxes together at the corners.  The threaded rods run vertically near each corner and hold the squares together.  Spacers made of balsa placed next to the threaded rods provide the open spaces in the frame.   Currently they are simply held in place by pressure coming from the nuts/washers on the threaded rods.  The white material is translucent plastic.  There is another sheet of it 1/2" below the visible sheet, sandwiched between a balsa square and a basswood square.  The thinking is that the top sheet will diffuse most of the unevenness in lighting, and the bottom sheet will take care of the rest.

Note the dimmer switch for on/off and to control brightness.  At full-on, the lights are pretty dim, so this may have been overkill.

Total weight of the box is 2.1 lbs. not including the weight of the cord.

lightbox_complete_top_small.jpg (23974 bytes)
lightbox_complete_side_small.jpg (29351 bytes) Here's a few more more views that help illustrate the construction...   
lightbox_frame_top_small.jpg (22661 bytes) The top has been removed in this picture.  Note the threaded rods protruding up from the top.
lightbox_frame_side_small.jpg (26974 bytes) Here you can see the "sandwich" arrangement of the lower diffuser sheet.
Here's the positioning and wiring of the bulbs.  Each bulb is a 7 1/2 watt nightlight bulb.  I wired them in parallel since in series they were too dim.  I think series was preferable in that I would always know if one bulb burned out which would prevent me from shooting a bunch of flawed (and useless) flats.  However, until I put foamcore board on the sides it's not a problem.

The illumination through the diffusers appears to be pretty even visually, with perhaps a slight falloff in the corners.  Since the corners aren't used anyway when shooting flats, I'm going to try it out and see how it works as-is.  I held up some white foamcore board to one side and noticed that the additional reflections seemed to help, so I'll probably add the foamcore board to the sides anyway.

lightbox_bulbs_small.jpg (28166 bytes)
lightbox_complete_scopeside_small.jpg (18539 bytes) This is the end that goes over the scope (I need to take a picture of this).  I put some felt on each side where the box contacts the scope to prevent scratches.  It is a smooth, tight fit, but I was a little disappointed that the box could not hold itself tightly flush to the scope- it slides down just a little, so I'll have to hold it flush onto the scope by hand when I shoot flats.

Update July 19, 2004: Over all it works pretty well (good, even illumination), though it is a bit heavy.  I'm hoping to experiment with electroluminescent panels to find a lightweight solution.

Last Updated: July 19, 2004
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