I had 2 transparencies processd in a pro lab. Both of the same subject. Both sheets of film had a light patch in the centre of the film! you can still see detail. the film is a few years old, agfa 100 rsx, 10x8. kept in the dark. i was using a sinar db 360mm lens at f64, 2 second exposure. No lens hood other than aleady on the lens.

i will try fresh film this weekend to see if it is the film as opposed to the lens which looks clear to me.

thanks

Bip