Start with the Blue Film, you can one shot the 1rst form of the Editor with a full charge zero shot. Before fighting his 2nd form, change the film for the green one (with the upgrade). After that, if you collect all the green films and the two pack of red films on the rooting, you should be good until the end, if you're don't spam too much or if you miss too many shots.

if you're want to save 6 free green film, you can switch for the blue film after the first fight with long arms. You have 6 photos to take for the enigma, until the beginning of the fight with the crawling girl, in the doll piece. Re-change film in the beginning of this fight. You can save 4 photos too in the night 3, when you take pictures of the marks before to fight the 4 priests.

Concerning the 24 red film you can have, it's up to you to use them at the ideal time. Ideally you can fight until 4 ghosts with the 24 red films, but it can change of course. Personally, i use the red films for the Folklorist for the two fights, and for the rest, i still make tests. For the Master, or for two of the priests seems good.

P.S : actually on my rooting i found a new pack of green film night 1, at the piece of the lake with the lantern to light. After you do that, just go for the corner of the hut, and continue the rooting. It's a time loss of only 10 sec, for 12 green film, for me it's more confortable to have this pack, you can spam more the ghosts during the run.

P.S 2 : you can have an extra shot of red film in the 1rst night, in the little room you taking photo of the seductress. Climb the ladder and it's just at the right. But you lost 30sec to make that, because climb and go down to the ladder take so much time :/ . But it's could be good for make some extra ghosts easier/faster, and you're completely sure you have enough film until the end.