As a follow-up to my series on the Basics of Manual settings, here’s a quick and awesome tool for reading light without a meter. On a sunny day, in direct sunlight, at f16: Your shutter speed will be the reciprocal of your film speed.
ISO 100 = f16 at 1/100th. ISO 400 = f16 at /400th.
You can easily extrapolate on the Sunny 16 rule. If you’re using a pinhole or a Holga with a fixed aperture, just work from Sunny 16 out. Here’s other apertures that use the film speed/ISO rule of Sunny 16.
Pretty useful for analog photography. Next… a Lomography post!