A Word on Light

Light Meters:

All DSLRs have built-in light meters which measure the light that the camera sees through the lens (TTL). Most DSLRs have light meters which can evaluate light in several different ways - please see your instruction manual to see which options your camera has, and for the differences between these settings. Until you get more familiar with your camera leave your light meter set as is.

The main three adjustments that need to be made to the camera are:

1. ISO (adjusts the sensor's sensitivity to light)

2. Shutter Speed (how fast the shutter fires)

3. Aperture (the size of the opening in the lens when the shutter fires)

Each of these have a section devoted to them, but this simple analogy below is nessesary to see how these three settings relate to each other.

Take a look at this simple set of numbers:
(20) 4 + 16

In the ISO/Shutter/Aperture relationship, the (20) above represents the ISO, and the second two numbers represent Shutter Speed + Aperture. Two things are illustrated here:

1. You can choose any first number that you'd like, but that will change the second two numbers
2. The second two numbers work in relationship to each other

To illustrate, all of the following examples work:

(40) 23 + 17
(25) 2 + 23
(10) 7 + 3

Now to put this in photographic terms to illustrate the relationship of these three items. First you pick your ISO, and then a combination of Shutter Speed and Aperture that take into consideration the choosen ISO.

With a DSLR, either aperture or shutter speed can be prioritized. That is, if a certain aperture is more important to you you can change the shutter speed to allow for your preferred aperture (more on why you'd want to do this in the aperture section here). If a certain shutter speed is more important to you, you can change the aperture to allow for your preferred shutter speed (more on why you'd want to do this in the shutter section here).

SUMMARY STATEMENT:
ISO, Shutter Speed, and Aperture all relate to each other. ISO is chosen first, and then the correct combination of Shutter Speed and Aperture taking the chosen ISO into account.