While shooting some portraits I put a back on with 3200 Ilford, to shoot the natural light indoors. I had to adjust the shutter to 125th. When I put the 100asa back on, I forgot to switch the shutter back to the sync speed of a 60th. I shot a total of 9 rolls that day, only one had complete pictures. The rest where half size. I had some explaining to do that day.