Homemade Exposure Unit, ~$100
The exposure unit I built was pretty simple and solid as a rock.

The materials were:

  • (4) 2x4 boards ($3/ea) = $12
  • (6) 1x4 boards ($2/ea) = $12
  • (2) 1x2 boards ($2/ea) = $4
  • (1) 1/4" plywood = $15
  • (1) 1/4" plate glass = $22
  • (1) power strip = $6
  • (2) 500W halogen work lamps ($10/ea) = $20
  • (1) box 3" deck screws = $5
  • (1) box 1-1/2" deck screws = $4
All told, that's right at $100. Fortunately, much of the lumber was already sitting in my shop. As was a fan that I have blowing across the glass, to keep the temperature down. At some point, when exposure time becomes a gating factor in my production, I will replace the two cheap halogen lamps with a sun-tanning lamp.

Here are some pictures of it:

A picture from the front. The basic construction is 2x4 legs with a 1x4 top rail and 1x4 cap rail, with a 1x2 rail supporting 1/4" plywood for the lamps about 20" from the top of the legs.
A corner showing the 2x4s butted against each other for the leg. Each leg is two 2x4s, making it rock solid and stable. I was going to inset the glass into the 1x4 cap, but I was more interested in completing the project than getting fancy. The clips are standard "mirror clips" bought at a local home improvement center. The glass 1/4" thick and was 1/2" larger than the opening on all sides (cut 1" larger than the opening).
Looking down from above the glass; you can see the clip-on fan to the right that blows across the glass.
The "Control Panel" — which is just a power strip that the two halogen lamps and the fan are wired to. The orange cable in the foreground is not part of the unit (I should have moved it before snapping the photo).