Camera 101: Basic Controls and Exposure

This is the first in a series of tutorials designed to teach you more about taking photos with a DSLR.

We're going to start off with a basic overview of the controls on your camera.  I'm going to use the very popular Canon T3i, but if you have a different camera don't worry - the basic controls are pretty similar from one camera to another.

What you can control

Before we have a look at how to control your camera though, let's first have a very quick look at what you can control.  I'll be going into all of these controls in greater detail in future articles:

Shutter Speed

Your camera has a "shutter", which opens for a short time to let light fall on your sensor.  You control how long it's open for (and therefore control how much light gets in) using the shutter speed.  This is typically measured in fractions of a second (e.g. 1/200th of a second) although you can set this to long values (e.g. 5 seconds, usually shown as 5".)

A longer shutter speed lets in more light, and a shorter shutter speed lets in less light.  Obviously, a 1/2 second shutter speed lets in half as much light as a 1 second shutter speed, because 1/2 a second is half as long as 1 second.

A fast moving object will have some motion blur with a long shutter speed, whereas a short shutter speed freezes motion.

Aperture

The aperture is a circular iris, much like the iris of your eye. The aperture, like the shutter, can also be used to control how much light makes it to your sensor; open the aperture all the way, and a lot of light will get in.  Close it down tight, and less light will get in.  Also, a wide-open aperture will create a very shallow "depth of field", whereas a tight one will create a large "depth of field."  We'll talk more about depth of field in another article.

Aperture is measured using a value called the "f-number", usually written as "f/3.5" or "f/8".  Note that the "f/" makes it look a bit like a fraction.  That's because it is!  Just like a shutter speed 1/30th of a second lets in less light that 1/15th of a second, an aperture of f/8 lets in less light than f/5.6.  The higher the "number" the more tightly closed the aperture, and the less light you get.  Some cameras will display this without the "/" or even without the "f" but don't let that fool you - it's still a fraction.

The other thing to know about aperture is that is not a linear scale.  f/1.4 lets in twice as much light as f/2, which lets in twice as much light as f/2.8.  (If you're curious, you let in twice as much light every time you multiply by the square root of two, but the details are for another day.)

ISO

The ISO number is a measure of how sensitive the sensor in your camera is to light.  At ISO 200, your camera is twice as sensitive to light as ISO 100.  A higher ISO will let you take the same shot with less light in the room.  As usual in this world, you don't get a free lunch; a higher ISO will also result in an image with more noise.

Read more after the jump!