I built my foamcore fresnel lens nested box camera from black foamcore board. It has black cardboard on both sides with black foam in between. The plastic-lined ultraboard refered to above may be more durable, but I don't know of a local supplier. Black foamcore board of the type I described is available from Hobby Lobby and Michael's.
Black gaffer's tape I get from a local film/video production supply house. About $20 per roll.
Here's the camera:
Here's a view through the removable viewfinder, which uses a sheet of translucent drafting vellum as a viewscreen:
(The digital camera was held upside down, to give a right-side-up image)
And an image, onto a paper negative. The plastic fresnel lens is stopped down to about 4mm:
Nice results. Also, neat way of attaching the camera to a baseboard/tripod. I was trying to think of some way of doing that too
Yeah the white foamcore is indeed translucent, which I discovered to my annoyance after buying several large sheets of it. The black stuff is pretty opaque though. I -did- have to add extra light proofing along the edges though. Black craft paper does the job there (I've made bellows out of it before). My impromptu perspex focusing screen is proving pretty crappy though, very difficult to even make out the image on it, let alone focus properly. I'll have to come up with some alternative I think.
Those are great portraits. I love the out-of-focus artifacts in both of these.
The lens is an Industar 37, a whopping €30 or so from some ukrainean Ebay seller. And all paper negatives, some Jessops RC multigrade that's been sitting in my press for about 2 years. Trying to source cheap X-Ray 8x10 film at the moment in Ireland, it's not looking good.