Need flashaholic insight in designing a light-box for negative viewing

[Daravon]

You know those things you seen on TV all the time where the doctors stick the Xray film so they can see through it? Well, I'm making one of those for viewing photo negatives and slides. Something a lot like this, but using materials I already have. I'm using one of those deep picture frames...it's probably 2.5 inches deep, and 11x13 or so. It has glass in it, as picture frames tend to. I basically need to stuff some lights in it and put something under the glass to diffuse the light. I would really like it to be battery powered and thus portalble.

There are two aspects I'm not sure of...underneath the glass, there should be something white to diffuse the light. I'm not sure what material I should use here. Thin plastic? Paper? Spray paint?

Also, I'm not sure where to mount the LEDs for optimum dispersion and evenness. I had figured mounting 6 cree LEDs on the SIDES of the frame pointing inwards would work for a diffuse light source, but 6 cree LEDs busts the budget. Maybe suggest bright 5mm LEDS? I could use CFLs, but then I would have to plug it in.

[purduephotog]

I've built light boxes for negs- mine is huge- 4' wide by 20" deep. I built it out of pine wood sides, 3x dual 4' fluorescent tube fixtures, and some white 1/4" acrylic I picked up for free (should have been 30$) from a plastics distributor.

Depending on what you have to display and how much you want to show I'd recommend going online and finding a used one- folks are clearing out light tables like crazy since film is disappearing. If you don't want to, just build a box that'll fit your light tubes, add some ventilation holes, and put a diffuser in (just like you've described).

My lightbox will do nearly 15 rolls of film, uncut, so I can review everything at once. I doubt you need *that* much.

Oh yeah- it's very very very very bright

(Yes, I know, I saw you wanted to use LEDs... but you can't get appreciable diffusion and intensity that you need at that distance. But)

If you use glass it isn't portable- it's fragile. Using acrylic will fit- you can get a small piece from a cutting board rollup mat from BBB. Space the LEDs so that they have no hot spots- you can't get great diffusion any other way (or double diffuse but that'll eat even more light).

The box? Get a project box from RadioShack made out of aluminum so you can heatsink directly and place sinks on the back.

Battery powered- little inset unit that can be removed... I'd consider buying a couple of lithium camera batteries and charger from eBay and using them (7.4V, 1900mah) to power it.