This is part one of my series on using your camera in manual mode.
There was a time when your camera’s ISO (light sensitivity) was determined by the film you loaded. Once you had your roll in place, you were stuck with that ISO for 12 or 24 or 36 exposures (or you had to waste exposures when you loaded a new roll). A digital camera—which captures the image on its sensor rather than a frame of film—allows you to change ISO as often as you like.
What’s important about ISO? A high ISO (400, 800, 1600) is considered fast, and it allows you to shoot in darker conditions. The trade-off is that your exposures are more likely to be grainy, at least on close inspection. That is becoming less of an issue as many of the latest cameras (e.g., the Canon 5D Mk II or Nikon D700) can shoot at those ISOs (and even higher) without much loss of quality.
The same may not be true of your camera, and by going manual you’ll learn more about its capabilities. If you’re shooting in full auto mode, your camera will choose the ISO. Don’t let it. Try setting the ISO yourself and see how that affects the speed and f-stop at which your pictures are taken. In general, you’ll want to use ISO 200 when shooting outdoors, ISO 400 when shooting in a reasonably-lit room, and ISO 800 or 1600 when there’s not much available light.
To experiment, try setting your ISO to 100 when shooting indoors. Your camera will have to compensate by using its widest f-stop (to let in as much light as possible) and a slow shutter speed in order to capture the picture. That slow speed will probably result in some blurring. Try also shooting at your camera’s highest ISO in that same environment. When you look at the picture later, zoom in and check its quality.
Shooting frames at different ISO settings isn’t much fun, but it’s an essential piece of the light factor puzzle. The next two posts, which will cover shutter speed and f-stop (aperture), will complete the picture and illustrate how manual control of your camera’s settings can give you more creative control of your pictures.