Noblex rotating-lens panoramic cameras have the lens inside a drum, which rotates to take a photo, recording a ~130° angle of view on film. Because the lens is inside this rotating drum, there is a unique way of installing filters, whereby the lens drum is manually rotated to access the lens, and the filter is inserted through the drum opening and magnetically attached onto the lens inside. Here is an illustration from the user manual:
But since there is no actual shutter inside these cameras, it seems that during this process, light can penetrate through the lens to the film chamber, ruining/wasting an exposure. The camera instruction manual says, "If you turn the drum counter-clockwise here, the film is exposed and you lose one picture", but it seems that even if you turn the drum clockwise, as per the instructions, you're still going to lose an exposure.
Is there any way to install a filter without exposing the film?