first day of class
Much like how carrots, celery, and onions are the three main ingredients that make up the definitive Holy Trinity of French cuisine, three key technical elements in the world of photography come together to make up the quality of a photographic image. The trio includes ISO, shutter speed, and aperture.
ISO Film Speed (sensitivity to light)
The general rule is the higher the ISO number, the more sensitive the camera is to the light. As the ISO number decreases, the better the color saturation, separation of tones, and sharpness.
As an example, a 50 ISO color film is 300% more saturated in color than reality for reds/yellows and 150% more saturated for blues/greens. On the other hand, a 1000 ISO color film is 25% less saturated than reality for reds/yellows and 40-50% less saturated for blues/greens. A 50 ISO 11″x14″ print wil be sharper than a 400 ISO 8″x10″ print.
Note that results are worse in digital than in film. A 1600 ISO film print is equal to an 800 ISO print in digital. (Digital is usually one level lower in ISO compared to film.)
Our goal is to always try to shoot at 100 ISO… never go above 400 ISO!
Shutter Speed How long are we going to let in the light?
The shutter speed defines the exposure time and is measured in seconds.
Note that the LCD monitor on most digital cameras displays the shutter speed as a fraction. As an example, ”0″5” would indicate 0.5 seconds and “15″” would indicate a 15-second exposure.
Aperture/(F-Stop) How much light are we going to let in?
The aperture is the opening through which the light comes in. The diameter of the aperture opening is measured using a standard F-Stop scale.
As a general rule, the larger the F-Stop number, the smaller the aperture opening. A stop is simply a unit quantity used to define the ratio of light, with an increase in one stop corresponding to the aperture receiving only half of the light. On the other hand, a decrease in one stop would imply the aperture letting in twice as much light.
Note that the range of apertures available will differ depending on the lens. The maximum aperture opening is usually labeled on the front edge of the lens. For instance, my 50mm lens opens up to F1.8 and is labeled as “1:1.8“.
