I have a 4 Mega Pixel Camera. I know how to raise or lower the aperture, but i have no idea what it does or when to use it. The aperture is the device the determines how much light comes through the lens for a given amount of time. The shutter, meanwhile, is what determines how long that amount of light is allowed to hit the sensor.
So the aperture has two uses, really. First, you can increase exposure by keeping the shutter speed fixed, by increasing the size of the aperture (smaller f number) or decrease exposure by using a smaller aperture (larger f number). In other words, if your shutter speed is 125th, for instance, and your aperture is f/8, you would double the exposure by increasing the aperture size to f/5.6.
The second use of the aperture is to control the depth of field, or, how much of the foreground or background is in focus. With smaller apertures (larger f numbers) more of the foreground and background will be in focus. So, generally, with landscape photographs, you'll want everything in focus and thus would use a small aperture like f/11, f/16 or f/22 (if your camera offers those).
But if you wanted to do a portrait, where the subject is in focus but the background is out of focus, then you'll want to use a larger aperture like f/4 or f/2.8. Of course to maintain your exposure when choosing a larger or smaller aperture, you would need to adjust your shutter speed up or down to match.
For instance, let's say your meter tells you that for the correct exposure, the camera has selected 1/250th at f/8. For a landscape, you might want to go to 1/60th at f/16 (same exposure) or for a portrait, you might go to 1/1000th at f/4. The smaller the aperture number the more light is allowed through the lens and the more reduced is the depth of field. The aperture is just the size of the hole that the light can get through. The size is indicated by the f number - the lower the number the larger the hole and the more light gets in. This is useful if you're shooting in low light conditions, but it also reduces the depth of field - objects nearer or further than whatever you've focussed on are more likely to be out of focus. This might be a good thing, depending on what you want to do. |
