Photographers use math to achieve correct exposure and to compose visually appealing photographs. Correct exposure is determined by the combination of shutter speed, f-stop and ISO. The golden ratio and the rule of thirds are popular visual guides.
Exposure is the amount of light that reaches either the camera's film or digital sensor. Too much light results in overexposure, while too little light results in underexposure. Shutter speed controls how fast the shutter opens and closes and range from minutes or hours for time-lapse photography to fractions of a second to freeze fast moving objects. F-stop controls the size of the camera's aperture, the lens opening through which light enters. Lower f-stops allow more light to enter than higher numbers. ISO regulates the sensitivity of the film or digital sensor to light. Higher numbers are more sensitive to light to lower numbers. A photographer must calculate the correct combination of shutter speed, f-stop and ISO to achieve correct exposure for a given environment and desired creative effect.
The golden ratio and rule of thirds both uses mathematics to achieve appealing photocompositions. The golden ratio is an ancient mathematical concept used to design everything from the pyramids in Egypt to photographs in popular fashion magazines. The ratio is 1:1.618. According to cambridgeincolour.com, the rule of thirds divides a photograph into vertical and horizontal thirds. Important compositional elements are placed at the intersection of the vertical and horizontal lines.