As a sail catches the wind, a camera catches light. This is the prime objective of a camera.
There are 3 parameters in the camera that determine the way in which we can capture light: Shutterspeed, Aperture and ISO to get Light. All the other factors and functions on a camera are there to enhance or change the effects of the captured light.
- Shutter Speed: setting the duration for which we open the camera: this is set using the ‘shutter speed’ function.
Camera or shutter speed is defined in fractions of seconds: if the shutter speed is set to 640, this means that the camera will open the mirror for 1/640th of a second to let light in. With shutter speed (SS) we control to what extend motion is frozen: the longer we open the mirror to let light in, the more motion blur will occur. This of course could be intentional. The shorter we open the lens, the more we will be able to freeze any movement a subject is making. For sports or nature photography (flying birds) this will be necessary. Shutter speed is used and set in all camera programs, but can be controlled and fixed specifically using the Tv (time value) program. - Aperture: defining how wide we open the lens that is mounted on the camera: this is set using the ‘aperture’ function. Aperture or F-stop values are defined in fractions of the lens opening. For example, an aperture value (or diaphragm) of 4 (f/4) sets the opening of the lens to 1/4 of the lens diameter (rule of thumb). If an aperture value of 8 is choosen (f/8) the lens is opened for 1/8 of the diameter. this effectively means that a quarter of the light is passed, compared to f/4. The effects of aperture to an image is depth of field. At the widest opening of any lens (e.g. f/1.8), the depth of field, or the area of the image that is ‘sharp’, is at its minimum. At the highest aperture value of the lens (e.g. f/22) the depth of field is at its maximum. On the web you can find a site to calculate the DOF for a given camera, focal length and distance: http://www.dofmaster.com/dofjs.html.
Aperture is used in all camera programs, but can be controlled and fixed specifically using the Av (aperture value) program. - ISO: setting the light sensitivity of the ‘film’ (camera sensor): this is set using the ‘ISO’ function.
ISO values of today can be compared to ASA values of the old film days. The higher the ISO value,
the higher the sensitivity of the sensor for light. Setting higher ISO values, allow for either more depth of field (aperture value) or for a higher shutter speed to better freeze motion. The effect of ISO to an image is image quality: the lower the ISO value (ranging from ISO.50 – ISO.102400) the higher the image quality
will be. High ISO values will reduce image quality and will introduce ‘noise’ or ‘film grain’. Noise can be best contained or controlled by exposing perfectly: the more light you capture, the less noise will appear. ISO settings are set and used in all exposure programs of a camera. ISO values can be fixed and set on all cameras (except in Auto Mode), but the way in which it can be controlled differs per camera.
