How to Choose the Correct ISO for Photography

The ISO setting on a camera determines how much light will be allowed into the lens. Its uses are important for anyone from a casual photographer recording a day with his family to a professional working for a magazine. Each setting of the ISO has major advantages and disadvantages. While low settings let in less light, they produce higher quality images. Alternatively, high settings let in more light (an irreplaceable feature for night photos), but add grains to the image. Understanding the ISO setting on a camera will result in dramatically improved photos, with minimal practice.

Difficulty: Moderately Easy

Instructions

1. Examine the ISO settings on your camera and determine the range. Most cameras range from 50 to 1600.

2. Judge the lighting of the area where the photograph will be taken. Daylight photos can use an ISO between 50 and 200, while extremely dark shots may require up to 1600. Use the lowest ISO that provides an adequately bright photo--higher settings result in grainy images.

3. Turn on and off the flash as necessary. Some areas restrict the use of flash photography, which makes a high ISO essential. Alternatively, the flash will sometimes allow you to reduce the ISO to capture a higher quality image.

4. Update the ISO if you are adjusting your camera's shutter speed to obtain a certain effect, such as trailing headlights on a car or silky smooth water. Because a longer shutter speed lets in more light, a lower ISO should be used to avoid washing out the image. Fast shutter speeds can be accommodated with a higher ISO.

5. Consider if the image will be enlarged. If it will, make an effort to change the setting to allow a lower ISO by altering the lighting, exposure or flash. Increasing the size of a photo will make the graininess caused by a high ISO more apparent.

6. Take a test photo after selecting the ISO and adjust it as necessary. The ISO should be increased if the image comes out too dark, and reduced if it is too bright. Continue taking photos until the lighting seems correct.

Tips & Warnings

• An image's brightness can be adjusted in photo editing applications, so the reduction of grain should be a priority. Use a tripod when increasing the shutter speed. The subtle shaking of a hand can ruin an image by leaving blurs.
• The graininess caused by a high ISO will not be visible on the small LCD screen of a digital camera. However, it will be obvious on a monitor and in print.