I was having trouble figuring out some lighter areas on my prints. They were 16 minute exposures at f16 & f22. Both looked about the same. I thought they may be from city lights over the hills.
It was suggested to me that I may be having problems in my developing so I set up a grey card on a grey paper backdrop in a studio setup. I used two monoheads with soft boxes and shot a series from f8 to f22. I carefully metered the flash to a tenth of a stop.
The result was an underexposed f8 and progressively worse shots up to f22. In other words, I don't believe the flash was going off at the same time as the shutter. They all look like the modeling lamps were all that came through. I was using 1/30 seconds because I thought that would be the most reliable. Both strobes fired every time.
What could cause this?