Exposure Defined In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance. Um, okay….? My definition: Exposure is about the control and manipulation of light to produce an image that matches your expectations.

Exposure Triangle

Shutter Speed Shutter speed is measured in seconds or fractions of seconds. ie – 1/125 or 1” Its primary function is to control the amount of light entering the camera.

Shutter Speed The faster the shutter speed the less amount of light enters the camera so the brighter your shooting conditions need to be. The slower the shutter speed the more amount of light enters the camera and the less light you need in your shooting conditions.

Shutter Speed The secondary function of shutter speed is to control motion. There are 3 types: Blur – the main subject is in focus but the parts of the subject in motion are blurry. Freeze – The subject is frozen in time Pan – the same as a blur only the background is blurred in the same direction as the subject is moving. Faster Shutter Speed = Freeze Slower Shutter Speed = Blur or Pan

Visual Explanation

Aperture Primary function – control the amount of light entering the camera. Aperture is measured in “f-Stops” or “F-numbers” The smaller the “f-stop” the larger the opening. The larger the “f-stop” number the smaller the opening. So a small f-stop value lets in the most amount of light and a large f-stop value lets in the least amount of light.

Aperture Secondary function is to control the depth of field. Depth of Field – is the distance between the closest object in your shot and the furthest object in your shot that is in sharp focus. 2 Types Shallow – the foreground, background or both in your shot is intentionally out of focus. Long – everything is in focus

Shallow Depth of Field

Long Depth of Field

ISO (used to be called ASA) ISO is measured in whole numbers that increase exponentially. ie – 25 50 100 200 400 800 1600 etc Its primary function is to control the sensitivity to light of the cameras sensors. (It used to be a measure of the film’s “speed” (sensitivity). The lower the ISO number the more light you need to achieve proper exposure but the less “noise” you have in your photos. The higher the ISO number the less light you need but the more “noise” you have in your photos.

Another way to think about this is that a low ISO number (25, 50, 100, 200) produces images with less noise but needs more light. Higher ISO numbers will produce images with more noise but can shoot in darker conditions. GENERAL RULE: SHOOT AT THE LOWEST POSSIBLE ISO.