Shutter Speed: This is the control you see depicted as 1/25 or 30 on your camera. These numbers represent how long the iris of your camera stays open when taking a photograph; or in simple terms, shutter speed is about how fast your camera is shooting. Slower speeds are used to capture things such as light painting or turning running water into more of smooth blur (anything under 1/10 or a tenth of a second). Faster speeds allow you to perfectly capture sports and energetic children. Aside from this, shutter speed is the initial way a photographer controls the amount of light in the image the faster the shutter speed, the less light and vice versa. If you want to have a play with shutter speed, flick your camera over to TV mode.
Aperture: You will see this on your camera screen as anything from f/1.2 to f/20. This setting effects how much of your image is in focus and how much detail is displayed. In terms of the camera lens, this controls how wide the cameras iris is. If the number is wide (or low), like 1.2, only a very select portion of your image will be in focus e.g. insect photos or soft focus portraits. Alternatively if the number is narrow (or high), 2.8 or higher, you will see more and more of the image in perfect focus e.g. landscape photography. As with shutter speed, aperture can also impact upon the amount of light in the photo the lower your number, the brighter the image will be and vice versa. If youve got a capable camera, switch to A or AV to play purely with aperture.
ISO: Here we have the only control on your camera which is specifically about light. Your ISO is normally measured on your camera from 100 through to 25,000 (on high end SLRs). The higher your ISO is, the brighter your photo will be. In perfect daylight, you would rarely go above 150, while at night it might be necessary to go closer to 1000. The catch here is that the higher setting is, the more noise or grain you will see in your otherwise crisp digital image. One rule of thumb is to do your best to never go above 800 unless you have a very capable camera (usually a top level dSLR). This setting can be tweaked in any mode outside of the basic auto setting.
The perfect photo requires a careful balancing of these three seemingly simple settings. It can take a lot of practice to understand how best to use each control. This is why, at times, even those who are experienced in professional photography are left staring at their controls when lighting or weather conditions change unexpectedly.
Armed with this knowledge you can better appreciate the efforts made by the photographer youve hired to capture your special moments. And hey, you can also have a go at taking some higher quality images yourself.