I printed first prototypes with what I had on hand - white PLA Pro filament. The prints were not opaque enough and I had to blacken their inside surface with black acrylic paint. As the project progressed towards a more mature design, I started looking for a better filament option.
A friend of mine recommended Prusa Carbon Black PETG, which I tried the first. Unlike the other PETG filaments I dealt with, this one is really opaque! I needed no additional work on the prints made with Prusa PETG - they all were light-leaking-proof. Later, I discovered a Czech company called EKO MB, their website is in Czech only. They produce r-PLA, r-PETG and r-PET filament from recycled plastic. Despite the fact that their price tag is slightly higher than the average, I decided to give it a try because recycled filament nicely fits into the concept of my project.
China filament is cheap, however I don't like the idea of shipping it over the half of the world. It is not eco-friendly in my opinion. Low price just removes the burden of making a choice, but what are real priorities and criteria?
EKO MB filament astonished me! For example, printing with their r-PLA or r-PETG, I had no stringing at all. That happened for the very first time in my two-year 3D-printing experience. I believe, the filament works well because it is fresh, i.e. the way from the filament producing machine to my printer was short. This fact encouraged me even to try pure PET filament. I consider this material to be the most "recyclable" filament nowadays, because most of the recycling infrastructure already processes it. This project creates an utility tool, not a toy, therefore properties such as temperature stability and structural strength are crucial. This fact prioritizes PET over PLA. I modified the printer with 0.6 mm nozzle to eliminate clogging of PET, which happens sometimes with the most common 0.4 mm nozzle diameter. I got excellent prints with EKO MB rPET as well.
My ultimate choice of filament for this project is r-PET. But it's not opaque enough and it requires a non-standard nozzle and a special two-component glue for assembling the parts of the printed camera body. Therefore, for the very first release of the project I decided to resort to good old PLA, preferably recycled one.
Also, I appreciated an EKO MB initiative to re-use filament spools. I sent them a dozen of empty filament spools, which piled up in a corner.