It's easy to make a test for example with a bookshelf as your subject. Centre your camera and look in the viewfinder with your eye centered, and mark where the four corners of the finder are with small, but easy to see objects/Post it notes, etc. on the bookshelf. Take a photo, develop your film and check the results. This will show how much deviation there is in the system at the distance you focused. I check parallax at the closest focusing distance. You'll get used to correcting your framing at close distances in a very short time.