I bought this pinhole body cap for my Pentax Spotmatic some time back, and I never tried it ...until now. I know near nothing about this type of photography, so it was a fun learning experience. I would recommend it to others. I used Black Cat Extended Range Exposure guide and settings for f/179 pinhole, even though I was not 100% sure that was the whole size (whoever I bought it from on eBay did not advertise this). I loaded the camera with Kodak Tmax 100 film, and developed it at home. I think the results say something like "try some more". And I think I will!