Exposure

Exposure can mean two vastly different things here at VoyeurWeb. There's the exposure of skin, and there's the exposure in photographic sense.

For exposure of skin, refer to Exposed in Public or Flashing

Photographic Exposure

The exposure of a photographic image is simple the amount of light recorded. Three basic camera settings vary the amount of light recorded: shutter speed, f-stop, and ISO. Many photographers use their camera's automatic exposure setting, and do a fine job at adjusting the exposure for varying lighting conditions.

Shutter Speed

The shutter speed is the amount of time the camera's shutter is open. The shutter allows light to reach the light sensitive media - film, transparency, or digital sensor. Think of a door opening and letting in the cold air. Leave the door open a long time, and lots of cold air enters. Quickly open and shut the door, and only a little amount of cold enters. Leave the shutter open for twice as long, and get twice as much light. Faster shutter speeds reduce motion blurring.

F-stop

The f-stop, or aperture, is the size of the opening in the lens. F-stop is technically the ratio of the lens focal length to the diameter of the lens opening. Most lenses have variable apertures/f-stops. A small f-stop number is a large opening, and a large f-stop number is a small opening. Using the door analogy, a large door lets in more cold than a small door. An aperture twice as large lets in twice as much light. Due to f-stops being a ratio of a circular diameter and apertures being an area, twice the light is factor of the square root of two.

ISO

The ISO, or ASA/DIN for old-timers, is the rating for how sensitive the recording media is to light. In the digital world, the pixels' gain can be adjusted to record a higher sensitivity to light; however, increasing the gain on the light also means increasing the gain on the electrical noise. Some newer cameras do an excellent job at noise reduction, but some inexpensive point and shoot cameras do not. In low light situations, a higher ISO will make the sensor more sensitive to the little light available. Using the door analogy once again, it is like opening the door to the cold air naked versus bundled up. Bundled up, you are less sensitive to the cold. Naked you are more sensitive to the cold, and a lot more fun for the pizza man to delivery a hot pizza pie to your door.

Stops

Given the f-stop terminology, photographers refer to a stop as increasing/decreasing the amount of light by a factor of two. Going from a shutter speed of 1/250 of second to 1/500 is considered one stop reduction, and going from 1/250 to 1/125 of second is increasing the by one stop. The same factor of two applies to ISO settings. However, for f-stops, the factor is the square root of two, so one stop from f/2 is f/2.8 or f/1.4 - the factor of the root of two. The standard scale in increments of one full stop is: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f22, f/32.