What does the 'f/16 sunny day rule' recommend?

The 'f/16 sunny day rule' is a guideline used by photographers to help choose proper exposure settings when shooting outdoors on a bright, sunny day. It suggests that when using an aperture setting of f/16, the corresponding shutter speed should match the ISO setting for correct exposure. For example, if you set your camera to ISO 100, then the appropriate shutter speed would be 1/100 second.

This rule simplifies the exposure triangle (aperture, shutter speed, and ISO) for situations with abundant natural light, providing a quick reference for photographers to achieve optimal results without having to rely heavily on metering or other complex adjustments. It is particularly useful for landscape photographers and during daylight conditions when lighting is consistent.

By contrast, settings related to ISO for bright conditions, shutter speed for night photography, and adjustments for white balance do not align with the specific recommendation of the 'f/16 sunny day rule' and are thus not applicable in this context.