My venerable old Nikkor 50/2 (I've owned since 1969) was again starting to show haze on the rear lens group. Trying to clean it showed it to be an oily deposit, so I disassembled a little further and completely de-oiled the diapragm blades. To test my work, I shot a test roll of Fuji 800 rated at 400. The film was drug store processed and scanned. Here's a picture from that roll shot wide open at 1/250 sec. It's very sharp despite showing a little 'glow' around the pure whites.