Use a tripod when shooting with a low ISO to stabilize the camera.
If your prefer ambient-light photography, learn adjust the ISO setting on your Canon EOS 40D digital camera. By setting the ISO from 100 to 3200, you can potentially eliminate the need for an external flash unit or the camera's built-in flash. Although exposing photos solely with natural light can lead to noisier images than using an artificial light source, the colors and shadows in the photo will appear natural and realistic.
Daylight Scenes
Use the Canon EOS 40D's lowest ISO settings when photographing well-lit daylight scenes with ambient light. These speeds include 100, 125, 160, 200, 250 and 320. Choose lower ISO numbers when shooting stationary scenery on bright days, such as blooming flowers in a garden. If clouds begin to move in, or small movement occurs in the scene, use a higher ISO number. This freezes motion and creates a correct exposure in lower-light situations such as taking pictures of children picking flowers in a shaded yard.
Shooting Indoors
As ambient light availability decreases, increase the ISO setting on your camera. The Canon EOS 40D offers three mid-range speeds: 400, 500 and 640. As the sun sets and you capture a few more pictures outside, use these higher ISO settings. Or, if you move indoors and rely on the ambient light from a window, lamp or overhead lighting, increase the camera sensor's sensitivity by increasing the ISO.
Dim Situations
If you're in an interior room without any available window light and must rely solely on light fixtures, turn the camera's ISO even higher. The Canon EOS 40D can capture images at ISO 800, 1,000, 1,250 and 1,600. When you choose the "H" option in the camera's custom functions menu, the camera can expose at ISO 3,200. Photos created at these higher ISO speeds will appear much noisier and film-like than digital photos recorded at lower ISO settings. To increase the sharpness and clarity of ambient-light pictures captured with high ISO settings, mount your Canon EOS 40D to a tripod. The extra stability enables shooting with a slower shutter speed, which allows more ambient light into the camera to expose the picture.
Night Photography
When there's barely any ambient light except for moonlight or stars, you can use any ISO setting you desire. A tripod becomes mandatory because exposures with so little ambient light will exceed the length of time you can hold your camera steady without it recording any movement from your body. For finer grain photos, use a low ISO setting. Your camera will expose for up to several minutes and gather every ray of ambient light to correctly expose the picture. For a more night-like appearance with a moody, soft-focus appeal, choose ISO 3,200. This higher ISO setting decreases your exposure time if you're in a hurry.
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