When using my Hasselblad 501CM in quite heavy rain and wind the other day, after about two hours I noticed these mysterious rings appearing on the Acutte Matt D viewfinder.
Once the Blad had tried out, they dissapeared.
What are they, and do I need to worry about it? Obviously a cause of the wet, but quite odd how they are perfectly circular and cylindrical. I assume they won't impact the image on film as the picture goes out the back through the curtains.