Revealing mistake: In the hospital after the car accident, we are first introduced to Carlisle. If you look at his face you can see where the white face makeup doesn't meet his hairline. Patches without makeup can be seen.
Revealing mistake: In the baseball scene, when the nomad vampires appear, you can see the rim of Laurent's contact lenses in close-up shots. (01:19:30)
Revealing mistake: When Bella and Edward are identifying the different stages of mitosis (prophase, metaphase, anaphase) in the lab it's not possible given the position of the microscope lens in relation to the microscope stage. The lens is positioned too far from the stage for an image of the nucleus to be correctly focused in the ocular. (00:16:55)