Continuity mistake: When Norton prepares for his suicide you see on the desk a photograph and, a bit away, a lamp. After he has shot himself the photograph is leaning against the lamp (it was too far away in the previous shot to have fallen against it). There's some sort of card open on his desk on some paperwork which suddenly moves onto bare desk as well. (01:57:10)NancyFelix
Factual error: In the scene where the guys are drinking beer on the roof, the bottles have "ribbed" tops. Beer bottles did not have twist-off's in the late 40's.
Continuity mistake: When the warden is given a bribe by his contractor/buddy, it comes in a box containing a pie and the pie is in a disposable corrugated aluminium pie tin. The warden gives the pie to Andy in a later scene and when Andy and Red eat it, it is in a metal pie pan... the non-disposable kind. (01:06:05)
Visible crew/equipment: When Sgt. Hadley nearly throws Andy off the plate factory roof, the reflection of a boom mike is briefly visible in the shiny brim of Hadley's hat. Andy dropped the tar mop before approaching Hadley, and there are no other objects in this shot that could have caused the reflection. (00:35:00)
Continuity mistake: When one of the "sisters" gets beaten up by Capt. Hadley he tries to escape from his cell and holds on to the bars on the other side of the passage. From the side his right hand grabs a diagonal bar, but seen through the bars he is holding on to a vertical bar. (00:43:15)NancyFelix
Other mistake: When the cons are drinking beer on top of the roof, the man that finished his bottle gestures for another. The guy takes out an already-opened bottle of the bucket horizontally, the beer should've poured out.
Continuity mistake: During the scene where Andy and Red meet for the first time (baseball scene) the sun is in Red's face and so, Andy shouldn't have the sun in his face. But in fact, sometimes Andy has the sun in his face and Red doesn't anymore. Either they move very quickly between scenes or (probably) the whole scene were filmed at least two times. (00:24:00)
Continuity mistake: When the warden shoots himself, he places the gun on the middle of his neck but when we see him lying there the bullet hole is now on the left side. (This is corrected on the tenth anniversary edition. The director also confirms this change on the DVD commentary.) (01:57:00)
Continuity mistake: In the same scene where Brooks is hanging himself, he carves his name and he is almost eye level with the spot where he is carving his name. The place where the rope is tied is lower. How come when he finishes carving his name he stretches to put the rope on? It is lower than where he was carving his name. (01:00:25)