I recently found the need for a simple flash diffuser (a macro project) and started looking around for suitable DIY material, as part of another project ( XA repair) I had bought some 35mm film (Fujifilm Superia), the plastic canister that the film rolls are packed in looked promising so I began by cutting the end off of the canister, the HDPE material that the canister is made of is very tough so I used a fine toothed saw to cut it off, you may be able to use a knife but it will have to be really sharp (don’t cut yourself!) once the end was removed it is just a matter of slitting it from end to end, this is easily done with scissors, and that’s it, clip it onto your built in flash and you are ready. The first two images below show tests shot taken with and without the diffuser in place, there is a slight difference in colour temperature, a slightly warmer tone (better skin tones?) but this can easily be adjusted in Darktable or in the camera’s WB settings, some colours are actually closer to reality, the green of the film canister is a good example, the flash image without diffuser is far too saturated, the diffusion is quite subtle, there is a slight bounce flash effect so shadows are softened and for example highlights on the chrome frame of the Newtons cradle are less conspicuous. It worked really well on the macro images I took, I should add that the ambient light source for the test images was fluorescent tube so not the best combination, not bad for something made out of scrap!