Every now and then I am given old bits of photographica to play with. Many of my older cameras do not have any form of metering so I usually use the sunny f11 rule (no, not f16 I’m in the UK). This neat little calculator dates from the late 1940’s and is surprisingly accurate. You simply move the dial for film speed, again for time of day and year, again for scene and finally for lighting conditions. You can then read off an accurate shutter speed and aperture.