Comment by jrflo
6 hours ago
I was curious about timing accuracy too, has any testing been done on this? Is it accurate to 1s, 0.1s, 0.01s? How dependent is it on the smart switch hardware?
6 hours ago
I was curious about timing accuracy too, has any testing been done on this? Is it accurate to 1s, 0.1s, 0.01s? How dependent is it on the smart switch hardware?
Repeatability is more important than accuracy.
Note also that some of the best printers used metronomes to count exposure time and turn the enlarger light on and off manually.
I played with development photos in a darkroom a long time ago. I don't think one second actually makes much difference.
Depends on how powerful of a light you’re using. 1 second on a 7 second exposure is too much. One second on a 20, not.
I don't think 1 second on a 7 second B+W exposure is that noticeable.
I'd probably put the typical smart switch hardware/software stack at around 0.25 seconds. Maybe you can but I don't think I'd try to rely on anything much faster than that.
If you did, I would go in the custom firmware for the smart switch direction. A lot of them are just an ESP32 inside, and you could probably get to 0.001 seconds that way (but you are switching AC which cycles on the order of 0.02 seconds, so whatever)
If I were to tackle this project, I’d use an ESP32 and a relay with 120V contacts. That way you can use a GFCI receptacle and be code compliant if your darkroom is in a basement or the enlarger receptacle is near your darkroom sink.