Having the chemicals and photo paper to hand, I thought I’d try a coffee-tin pinhole camera. I drilled a 2mm hole into the tin and sanded the inside of the tin to remove the burr. I had read a perfect hole is needed for the best images. I lined the inside of the tin with black paper and cut some photo paper to fit inside.
I found that my camera has an f stop of 35. Using my iPhone’s Lux app to measure the exposure on the basis that the photo paper is ISO6 I got an exposure time of 10 seconds. My results have encouraged me to explore this further.