A tool exists to assist photographers in rapidly determining appropriate camera settings under specific lighting conditions. This aid, derived from a well-established photographic guideline, provides an initial aperture and shutter speed combination for correctly exposing a scene lit by direct sunlight. For example, on a bright sunny day, if the ISO is set to 200, the suggested settings might be an aperture of f/16 and a shutter speed of 1/200th of a second.
The primary advantage of using such a tool is its capacity to deliver a baseline exposure reading without the immediate need for a light meter. This is particularly beneficial in situations where a meter is unavailable, unreliable, or when a quick estimation is required. Historically, this guideline served as an invaluable asset to photographers, especially those using film cameras, by reducing the likelihood of under- or over-exposed images. It is also a method for learning the relationship between aperture, shutter speed and ISO.
