Photography Basics: Lesson One
When first upgrading from a Point and Shoot digital camera to a Digital SLR, all the knobs and lenses and terminology can be quite intimidating. I don't have any tips to make it easier, other than to practice, practice, practice!
Today we'll start from the very beginning with exposures: apertures, shutter speeds, and ISO.
First, let's define these terms.
Aperture~an opening that is used to control the amount of light passing through the lens of a camera. Typically constructed as an expanding and contracting iris. Measured in f-stops.
f-stop~values are the ratio of the focal length of the lens to the diameter of the opening in the aperture.
Shutter~a mechanism that sits in front of the focal plane in a camera and can open and close to expose the image senor or film to light.
ISO~a measure of a film's "speed" or light sensitivity. The higher the ISO, the more sensitive the film. Digital camera sensors are also rated using the ISO scale.
OK, good, everything is now perfectly clear right?
As you increase your shutter speed, you need to decrease your aperture. This lets in more light compensating for the fact that the shutter is open for a shorter time. This relationship is called reciprocity because of the reciprocal relationship between the two values. Apertures and shutter speeds typically double with each setting.
Confused yet?
The higher the ISO rating, the more sensitive the film is to light. A film with a higher ISO rating doesn't need as long of an exposure to make an image. A high ISO rating facilitates shooting in low light situations and in bright daylight with faster shutter speeds and smaller apertures. The drawback is that faster film means images with lots of grain.
ISO is the third factor you can control when using a digital camera giving them tremendous advantage over traditional film cameras.
Next topic: Shooting modes
Posted in: aperture, f-stop, ISO, photography basics, reciprocity, shutter speed on Sunday, April 6, 2008 at at 10:52 AM
