Understanding ISO helps you control the results you get from your camera.
Sensitivity to light in photographic systems is described as ISO speed. While this system was developed for use with silver-based film systems, digital cameras have adopted it to describe light sensitivity of imaging sensors. The lower the !SO speed, the less sensitive the film or sensor is to light. Doubling or halving the ISO changes sensitivity by a factor of one stop, useful in calculating changes of exposure with shutter speed and f-stop combinations.
Instructions
1. Evaluate your shooting conditions. As a general rule, the brighter the light, the lower the ISO speed required. In both film and digital systems, low ISO equates to better quality in terms of grain, sharpness and color saturation.
2. Select ISO 100 for bright daylight or for use with electronic flash with subjects reasonably close to the camera. With daylight, a possible exception may be where you want a very high shutter speed to freeze action. Selecting ISO 200 or 400 may work better in that circumstance. As electronic flash synchronizes at shutter speeds of 1/125 or 1/250 on most cameras, there is no advantage in freezing action. The flash duration is usually much shorter and addresses freezing motion.
3. Choose ISO 200, 400 or 800 for candid photography indoors without flash if there is much available light. Used with flash, these speeds effectively increase the distance the flash illuminates, though subjects close to the flash may be extremely overexposed.
4. Select ISO 800, 1600 or 3200 for low-light situations where you must shoot handheld. Increased sensitivity will allow faster shutter speeds but at a cost of increased gain and loss of shadow detail. Typical situations for these settings include concerts or sporting events and candid available-light photography indoors without flash.
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