The 120 negatives of HP5 are thinner than the 35 mm negatives because the development time for the 120 film is longer in PMK pyro than the time for 35mm HP5. Don't ask me why. My 120 negatives were thin, too, and I thought it was the camera since I use the same handheld meter for 35mm and 120 photography. Then I noticed on the inside of the 120 film box how the development times for HP5 were different if the developer was HC110. Times for other developers were the same in both formats, but the HC110 time was longer in the 120. So I tried a longer time for the 120 in PMK pyro and now the negatives are fine. Again, don't ask me why--same water, same tank, same agitation, same temperature/thermometer, same idiot agitating the tank. For 35 mm at 80 fahrenheit--8 minutes. For 120 at 80 fahrenheit--9.5 minutes.(posted 8171 days ago)Lee England Natchez, Miss.