The Exposure Triangle

a brief overview of basic settings to get out of auto mode.

In this lesson we are going to explore the basics of exposure.  An exposure is the act of allowing light to strike a light sensitive surface. The amount of light reaching the film or sensor is controlled by the combination of light-sensitivity, aperture and shutter speed.

In photography, there are three major settings to consider:

ISO:

ISO is a measure of the photosensitive emulsion on a strip of celluloid film, or the speed rating for a digital camera’s sensor. A numerical rating that indicates the speed of a film. The higher the number, the more sensitive your film/sensor.  You can find films ranging from a sensitivity of 1 up to 3200. Some digital sensors go even higher.  Be aware; the higher the ISO, the grainier (noisier) your photos can get. Lower ISO films can create beautiful images with rich saturations of colors and grays but they need to be exposed with enough light or enough time to get a proper exposure.

Aperture:

Aperture is the size of the hole formed by the iris diaphragm inside the lens. It is the opening that lets light into your lens, which gets recorded by your film/sensor as a photo.  Aperture is measured in “f-stops”

Shutter Speed:

The amount of time that the shutter is held open for, which allows light to pass through the aperture of a lens in order to hit the light sensitive emulsion or sensor to create an image. Shutter speeds can range from days, to hours, to multiple seconds long exposures, to tiny fractions of a second. 

The fastest camera in the world, called the SCARF, uses laser pulses to shoot 156.3 trillion frames per second, which is sort of mind boggling. Most readily available cameras have their fastest speeds of between 1/4000th of a second to 1/8000th of a second.