Rodinal isn't known for getting the most speed from films. I find it as much as a stop slower than box speed with some films (unless adding Vitamin C or doing semi-stand). As Jim A. mentioned earlier, there are other developers that tend to yield higher effective film speeds.
Even automatic cameras that set film speed from a DX coded cartridge don't take this kind of adjustment into account.
Try to make a habit of changing the film speed on the camera body or light meter just before you load the film. I try to do it just before taking the film out of the packaging for loading.
At least you'll remember to check the meter's ISO setting for a while now.
I once blew a shot of a vivid monster rainbow with a very dark cloud behind it over a sunlit lake and lodge in the late afternoon when I grabbed a roll of Kodachrome 25, mistaking it for 64, and underexposed the lot. I discovered my mistake just as the rainbow was gone. I could probably have made a good sale to the lodge if I'd taken the three seconds to check film speed. The camera I was using even has a window to view the film cartridge.
Live and learn.
Lee
