I built the entry level, paper-foldable spectrophotometer just before New Years. The experience I had and the lessons I learned are below.
1.) First, I tried it out of paper. That is super easy because you just have to print out the form, cut and then fold, but the paper is not thick enough to block out extraneous light. I was able to improve it by wrapping the front of the small box with black electrician's tape. It worked . . . sort of.
2.) Getting the aperature right is a big deal and not that easy to do. I ended up 3d printing an appoximate aperature and then using electrician's tape to make the aperature closer to the 0.4mm that is suggested. Unfortunately, my 3d printer is not accurate enough to just print a small slot like that.
3.) I'm getting spectral images from the CFL lights but the resolution is no where near the 1 nm that is mentioned as possible.
Therefore, I'm ready to buy the desktop reference design with the web cam and the aperature kit. I think that will be easier to use (it is hard to hold the box onto your smartphone camera while snapping a picture) and hope that it will be more precise.