Why do you need to know about exposure to take good pictures?
The snaps you’ve been taking on your camera phone look great don’t they? Most of the time at least. Well, except when things are really dark or really bright, when it just seems to get things wrong, and the shots don’t come out how you intended. And whilst we’re on the subject, how is it possible to get that perfect shot of your friend going over that ski jump absolutely crisp and sharp as if they were suspended in the air? How do professional photographers manage to get those shots where someone’s eyes are in focus and the rest of the shot is all soft and dreamy? And how do landscape photographers create that magical effect of making water going over a waterfall look like it’s white mist?
The answer to all these technical and creative questions, along with many more, lie in understanding how exposure works. Getting your head around how your camera (whether it’s a camera phone, a DSLR, or anything else for that matter) arrives at an exposure is a vital first step towards taking better pictures. Once you know what’s happening inside that mysterious black box, you’ll be able to make technical decisions that will allow you to create the images you’ve been dreaming of.
On a very basic level, exposure simply means how light or dark the image is - nothing more than that really. However, thinking in these terms is OK when you’re just starting out, but we’ll soon see it’s made up of many more parts, all of which are closely related.
The “Right” Exposure
Short answer - there’s no such thing as the “right” exposure. That was easy wasn’t it? In practice though, the “right” exposure is the one that’s correct for the effect and image you’re trying to create. Cameras in any automatic mode will always try and average out an exposure to conform to a set of exposures that have been calculated to give the best all-round results. Of course, if you’re looking to create a certain image, this average result may be very far from what you intend, and that’s where knowing what different parts of the exposure system do, and how to manipulate them, gives you a huge head-start.
The Exposure Triangle
OK, enough of the vague waffle about dreamy exposures, how does all this work? Probably the best place to start is with the famous (to photographers at least) Exposure Triangle:
There are 3 things which affect the exposure of an image, the aperture, the shutter speed, and the sensitivity of the recording medium. Before we go into what each one of these does, there are 2 things that you must understand.
The importance of manual mode
The last thing I want to talk about before we start getting our hands dirty with the real meat of exposure control is manual mode. For all the stuff I’m going to take you through, I want you to put your camera in manual exposure mode.
Manual Mode - look for the "M"
The reason for this is that you need to be able to alter every setting possible, and witness the effects, and if you’re using any automatic mode at all, the camera will be making some decisions for you. This will rapidly start to become confusing, as I’ll be describing how changing such and such should lead to such and such an effect, and you won’t be seeing any change! If you’re using a camera phone, finding a true manual mode may be a little tricky, but some of the latest smart phones do allow you a great deal of manual control. However, I don’t think any of them allow you full control, so to get the best understanding of what I’m going to talk about, you need a camera that will let you adjust the aperture, shutter speed and sensitivity.
So without further ado, let’s get down to the precise details. For each exposure control I’ll describe what it is, and then what effect it has on your images.
Different camera types. From Left to Right - Digital compact, 35mm film SLR, DSLR, Smartphone. You'll need a camera that lets you have full manual control in order to learn how exposure works, so I'm afraid a camera phone probably won't cut it!