Understanding exposure and how it can help improve your photography - part 2

If you've read the first part on understanding exposure, you're ready to go a little further.

On this page, I've covered what the aperture is, and then, keep reading and I'll show you why all this is important!

Understanding exposure – Aperture

The Aperture? The what? In understanding exposure you need to know what the aperture is and does.

As with shutter speed, the aperture is also a way of controlling how much light enters the camera.

The aperture is an adjustable hole in the lens. It can open to allow more light in. Or it can close to become just a tiny hole, stopping so much light from entering.

Aperture and shutter speed work together - if you have a slow shutter speed (to let more light in) you have to close the aperture to compensate. And visa versa – if you have a fast shutter speed (letting less light in) you have to open the aperture to allow in more light to compensate.

Click for an explanation of how aperture can be used creatively to control depth of field.

Understanding exposure – "film speed"

Film speed? On a digital photography site? I must be kidding! Well. No. For understanding exposure it helps to know about film speed, or ISO. Let me explain . . .

In the old days we would load film into our cameras. The most common film was called ISO 100. The ISO rating was a measure of how sensitive the film was to light.

ISO 100 was fine for everyday use in good light. But if the light levels dropped, you had to compensate by having a slow shutter speed, and a nice wide aperture.

The problem? Once your aperture was fully open (to let as much light in as possible), and your shutter speed was as slow as you could manage and still hold the camera steady (to avoid blurring the shot), and there still wasn't enough light . . .You loaded more sensitive film into your camera!

The sensitivity of film doubled from ISO 100 to ISO 200. It then doubled again to ISO 400 . . . and so on. The highest you could go as a consumer was ISO 1600. ISO 6400 was available, but only really sold in the pro shops.

So what's this got to do with digital photography? Digital SLRs allow you to set the ISO manually. So if it gets dark, you can increase the ISO. The downside is digital noise – a speckling effect on photos.

This speckling occurred in the days of film too. The higher the film speed, the more speckling. Back then we called it film grain, and it can be used to good effect.

If you've read enough about understanding exposure why not explore the rest of the site.