>>4391566Here's German DIN norm for shutters:
https://www.dinmedia.de/en/standard/din-19015/1042560 the essence of it is picrel, so ideally your timings have to fall in these values, if don't and cleaning doesn't help print out actual timings and use those as settings. For example 1/125 measures as 1/76 so if you want to shoot at 1/60 use 1/125 setting on camera. That's what I do, works great.
Now how to measure. The best way is to do a standalone tester based on arduino and light detecting diode, I've used this one and it works great:
https://github.com/hiroshootsfilm/shutterspeedtesterarduino micro is hard to get these days, but there is chinese seeduino xiao (arm based which is funny) and it works great.
Don't have to solder anything, build it on test board
