First Steps In Photography – Exposure Compensation

Look Ma – No Controls
Some point and shoot cameras are just that – ‘point and shoot’.

In other words, the photographer has no control over any of the functions such as the shutter speed or the aperture.

Shutter Speed and Aperture
A quick explanation. The shutter speed is the length of time the sensor (or the film in a film camera) is exposed to light. Shutter speeds range from 1/8,000th of a second or even less, to as long as several seconds. Obviously, you would need to put the camera on a solid surface or on a tripod to hold it steady for several seconds.

Aperture is the size of the hole in the lens that lets in the light. The size of the hole is varied by an iris that closes and opens. It is set for a particular exposure either manually by the photographer – or for certain settings it is done automatically by the camera.

Scene Modes
Some more advanced cameras have ‘scene’ modes that the photographer can dial in. That tells the camera whether it is being pointed at a face, a landscape, a moonlit scene, or one of the other pre-set scenes built into the camera.

The reason for these scene modes is that the camera does not know what it is being pointed at. This matters because some scenes need to be exposed differently from the norm if the photographs are to come out looking as they were intended to look.

Scene modes are a way for the photographer to tell the camera how to expose the scene.

Exposure compensation
Better cameras, and that includes some compact cameras and more or less all SLRs, go a step further and instead of (or as well as) having scene modes, they have a dial so the photographer to set exposure compensation.

For a reason that we will get to in a moment, the photographer will want to dial in some exposure compensation. He can dial in positive exposure compensation (giving more exposure to the subject) or he can dial in negative exposure compensation (giving less exposure to the subject).

Some cameras allow the photographer to set as much as 5 stops of positive exposure compensation and the same amount of negative compensation.

I haven’t done a check of all the cameras on the market, but I would guess that all SLR cameras can dial in at least 2 stops of exposure compensation.

And The Reason They Would Want To Do This Is…
The reason that a photographer would want to dial in exposure compensation is because a scene needs an eposure that is different from the norm.

But what exactly does that mean?

Well what is means is that cameras are not magical. They assume everything they see is more or less mid-grey after taking into account all the lighter and darker parts of the scene.

But what about a white cat in a white room? What about a black cat in a darkened room?

How can the camera expose the shot correctly when it thinks everything is mid-grey? And of course the answer is that the camera cannot expose the shot correctly. That is where exposure compensation comes in.

It Pays To Know Your Onions
Take a look at the two photographs of the onion, below.

I shot this onion against a sheet of black card. The first was shot without any exposure compensation. The second was shot with minus 2 stops of compensation.

The scene was not mid-grey. It was dark. So to make it look like it should, namely ‘dark’, I dialed in 2 stops of negative exposure compensation.

That makes the onion look the dark, rich red that it should be. It makes the leaves the green they should be; and it makes the background black like it should be.

The Rule
And this is the rule to follow. If the scene is dark, dial in some negative exposure compensation. If the scene is very light, dial in some positive exposure compensation.

How much compensation? Well from mid-grey to black or from mid-grey to white is about 2 stops, maybe a bit more.

If you are using a digital camera, just dial in some compensation and look at the results. You’ll soon get the hang of how much compensation to use.

Tagged as: exposure compensation