There are different types of camera, but basically, they work like this:

Light enters through a hole (APERTURE) at the front, generally FOCUSED through a LENS.

A SHUTTER exposes a SENSOR (or FILM)

The light hits the sensor or film and is recorded/ converted into an image.

Essentially, a camera is a box with a hole in it which captures light.

HOW DO CAMERAS WORK?

So, when it comes to using your camera, there are a few things you have control over. At a very basic level, all you are doing is controlling how much light hits the sensor. There are three elements to this:​

  • The size of the aperture (f-stop)

  • The shutter speed

  • The sensitivity of the sensor (ISO)

These three things combined constitute EXPOSURE, and understanding and mastering it is probably the basic requirement of successful photography.

Although this image has a LARGER f-stop, a LOWER ISO and a FASTER shutter speed means overall there is less light hitting the sensor and the sensor is less sensitive to light. The buildings look a bit too dark, especially at the corners - they are UNDER-EXPOSED. The sky is a nice colour, though,

A smaller f-stop, but a higher ISO and a slower shutter speed mean more light is hitting the sensor, and the sensor is more sensitive. As a result there is a lot more light on the buildings and most people would probably say they look better. However, the sky is OVER-EXPOSED; the white is BURNED OUT, meaning it has lost all detail.

NOTE - f-stops are weird. The bigger the number, the smaller the aperture!

So, there are a number of ways to control how light reaches the sensor. It's important to realise, though, that adjusting one or the other is going to have a different effect, and combining them in different ways achieves different results.

  • SHUTTER SPEED; Adjusting this up or down allows the sensor to be exposed for a longer or shorter amount of time, so if you are photographing something that is moving, you will possibly end up with motion blur or light trails. Sometimes you want this, sometimes you don't.

Picture Credits: Thanks to Charles Ma, Natalie Kainz, Ingrid Ho, Charlotte Ng, Yoki Tomiyama, Paridhi Surana

This photographer has chosen to leave the shutter open for a full second. That is a long time; cars will travel quite a distance in that time and thus we capture the movement; hence, the light trails.

  • APERTURE: A wider aperture lets in more light. But it also changes the DEPTH OF FIELD; the amount of the picture in terms of depth (think foreground, midground, background) which is in focus. Depth of field is affected by a few things, but aperture contributes to it; a small aperture (which is represented by a larger number, remember!) will give DEEP FOCUS where everything in the image, whether close to or far from the camera, will be in focus.

Here, the shutter speed is 1/1250 seconds. That's fast and it has the effect of freezing the action as the subject leaps over the wall.

Here, the shutter speed is 1/1250 seconds. That's fast and it has the effect of freezing the action as the subject leaps over the wall.

An f-stop (aperture size) of 11 is quite small, so more of the image is in focus.

Smaller number (f/4.5), so bigger aperture! That means we have shallower focus - this photographer has focused tightly on the signs and the fruit, while the people in the background are blurred out to create a more distinct separation between the planes of the image.

  • ISO - This is probably the easiest and most immediate way to adjust exposure, but it's not necessarily the best one. As a general rule, the ISO should be as low as you can get it; turning it up too high creates NOISE (interference) in the image.

LENSES

In many ways, the lens you use will make a bigger difference to your images than the camera body you choose. It helps, then, to understand what a lens is and what it is actually doing.

At a basic level, a lens is simply a series of glass elements which focus light onto the rear element of the camera in different ways according to their shape, the distance between them and so on.

Other indicators and controls to assist in focusing light are arranged on the outer body of the lens.

FOCAL LENGTH

There are a lot of things that make one lens different from another, but the basic thing to understand is focal length. It's measured in millimetres and it is the distance between the point where the light converges to the camera sensor (or film.) So here, for example, the focal length is 28 mm.

There are a lot of things that make one lens different from another, but the basic thing to understand is focal length. It's measured in millimetres and it is the distance between the point where the light converges to a point and the camera sensor (or film.) So here, for example, the focal length is 28 mm.

Who cares? What difference does it make? All the difference in the world, really. Focal length is going to affect the amount of the subject you can see, the perspective, the depth of field. Some good examples from this excellent site:

12 mm.

12 mm. Exaggerates distance from foreground to background. Whole scene included in image.

35 mm. Background to subject is more compressed.Rather less of the scene is captured.

200 mm. Perspective severely compressed, less of scene has been captured.

100 mm. A focal length commonly used for portraits.  Perspective is more compressed so image has some unity. Less again of the scene is captured.

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