Same setup, recorded with my Canon camera and a ND64 filter:There are some visible problems. First the brightness doesn't change logarithmically. This results in less perfect color blending, because there should be more brightness steps when it is darker. Second problem is that you can see the brightness steps, if you look carefully. This would require a finer PWM resolution, currently I use 8 bit. I don't know if I can fix both with the PIC, with 512 words flash and clocked at 4 MHz it is a bit slow, but maybe it is possible when I write it in assembler instead of C.