Dirty rollers are the most common cause of visible film defects. In order to spread the developer paste between the negative and positive components of the photo, each picture goes through the two metal rollers as they exit the film door. If they are dirty or just a little uneven, the chemistry will not be evenly spread across the photo.
We recommend that you inspect your rollers between every pack of film, and clean them every 2-3 packs – even if they look perfectly clean to you. The rollers are accessible by opening the film door compartment of the camera (the film can remain in the camera while cleaning)
You can easily clean them with a soft cloth, dampened slightly with clean water. Allow the rollers to dry completely before using your camera again.
The below photos are examples of common roller-related film defects:
photo Ilona Cerowska
photo Liana Joyce