I picked up a few rolls of expired (05/2005) provia400F from a local store and shoot one of them with contax g1. this was the first time I use this film and i shot it at ei400. However most frames in roll are under-exposed. those frames are taken in shadows, without much back light. Funny thing is some frames taken under the sun look ok. I am not sure if this is the problem of the film is expired. I mean indeed its only like half year or so. should I rate the film differently? Thanks.