100 and 400 ISO

We were extremely concerned with film speed in our black and white days. For those who care to know a bit about the minutiae of old school film shooting, the higher the ISO, the more low light you could successfully shoot in. (ISO = 'International Standards Organization').  A high ISO also meant you could get more action shots without blurring (faster shutter speed). The only drawback was,  the larger you tried to blow up the photo, the grainier it became because the silver particles embedded in the high ISO film were literally larger.

The first photo below was a co-worker at VVI night school, shot at 100 ISO, and blown up to 8 x 10. The second photo was a classmate at VVI, shot at 400 ISO and blown up to the same proportions. You can see the difference in grain. (I was amused at the time of taking the second shot to catch my classmate in an unguarded moment of disapproval about another classmate).