Before starting the 2nd fight of Editor, take the green film, and upgrade the speed. Upgrade the speed again after the assistant (Tomoe). Then, upgrade the max speed after the RNG Kid in night two (who have a piece of the mirror). And finally upgrade the max value (just one time, more is not useful and a handicap for Kirie in the end) before fighting the Folklorist (Ryozo).

With these landmarks, you should can have enough points for upgrade the camera in the perfect timing, even if sometimes, you can have bad luck, not enough points, but it's rare.