When we see Anna photographing Alice weeping, she is using a 35mm Leica camera. At the gallery exhibition however, the picture of Anna is a full frame, medium format print complete with black borders, therefore taken with a medium format camera - a much more wieldy instrument.
In the Park which Dan and Alice walk through at start of film scaffolding with plastic covering can be seen in the background. At the end of the film when Dan is there the same scaffolding can still be seen even though 4 years have passed.
When Anna first begins photographing Alice, she is using a Leica 35mm range-finder camera with a manual film advance. However, when Anna takes the last few photographs of Alice weeping, the shots are rapid fire and you hear the sound of an automatic film advance.
In the opening scene when Alice is walking down the street, the front of her hair is dyed a very bright red but in the next scene when she in the hospital waiting room with Dan, there are only a few streaks.
While Larry and Anna are having lunch to sign divorce papers, Larry is wearing his wedding band, when Anna reaches for her pen, and Larry's hand is on his leg, he isn't wearing his ring, nor when he grabs her hand on the table, and in the next scene he is wearing the ring.
When Alice and Dan are entering the garden at the beginning of the film, a woman in a khaki coat is seen leaving the garden as they enter but in the next shot is nowhere to be seen but is then seen walking away in the following scene.
When Dan is cybersexing with Larry, and begins to simulate an orgasm, he type a full line of $%$^&^&*&()*()*_)( but in the next shot he is only adding the first line of $%^&*^(*^&^ $%$#$%#@%^&&*^&*(*&(
When Dan and Anna are at the opera (the English National Opera in London), the soundtrack is playing a recording of Mozart's "Cosi Fan Tutte" in the original Italian. All productions at the ENO are always sung in English.
The opening action has Dan taking Alice to the hospital, staying with her in the waiting room, and the two leaving together. Unless a patient is unconscious, hospital intake always involves an interview procedure where the patient has to give their name, insurance information, and relevant medical history. To call a patient out of the waiting room, the hospital staff uses the name on the intake records, rather than shouting "hey you" to the next person to be seen. Yet, when Dan and Alice are getting ready to part ways after the bus trip away from the hospital, he says, "I don't even know your name."