Photography is an imprecise science. There are few, if any technically "perfect" photographs taken with a film camera.
-What is the true speed of the film?
-How accurate is the film developing?
-How accurate is the meter?
-How accurate is the shutter speed?
-Did you measure the scene properly with your light meter?
-Is the film moving in the film plane during the shutter traverse?
-Do both shutter curtains move across the film plane at the same speed?
-Does the lens hold it's focus exactly during the shock of stop down?
-Does the lens hold it's focus exactly during the shock of the shutter releasing?
-Is that lens of yours as perfect as you have been led to believe?
-Is the footing under the tripod really solid?
-Is the tripod large enough for the camera?
-Does the tripod have enough mass to dampen any shutter or mirror shock?
-Is your lens made by the right manufacturer?
-Did Ansel recommend the camera you are using to anyone?
-Do you really know what you are doing?
-Is the lens barrel chrome or black?
Scary stuff eh?