Understanding ISO: A Beginner’s Guide
WHAT IS ISO?
ISO is one of the three elements affecting exposure. The other two elements are aperture and shutter speed. ISO determines the sensitivity of the camera’s sensor to available light. The sensor's job is to gather light to create an image.
WHAT ARE THE ISO VALUES?
Most DSLRs have with a minimum ISO value of 100 or 200. The value doubles (200, 400, 800, 1600, 32,000, etc) for each increase in the setting. Every time you increase the ISO value, you double the sensor’s light sensitivity.
HOW DOES AN ISO VALUE AFFECT EXPOSURE?
In simple terms, the higher the ISO value, the less light you need to capture a photograph. Using a higher ISO number may, however, “damage” your image, producing some digital noise. Noise can look like granular splotches of color as shown in the image below.
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WHEN TO USE A LOW ISO VALUE
Who doesn’t want crisp images? A low ISO value will produce cleaner images with less noise.
Here are a few simple guidelines for using ISO settings of 100 to 800 (depending on your camera’s capability):
A) A Well Lit Room: Use a low ISO to take advantage of natural light inside a room. It will add a fresh, clean and crisp feel to your photo.
B) Using Flash: If you are shooting indoors and the lighting is poor, you can use flash to help you keep a low ISO value.
C) Day Light: Low ISO works well outdoors when it’s sunny.
D) Sunset: As the light gets lower, you may have to increase your ISO setting, but using the lowest possible setting will keep your images sharper.
WHEN TO USE A HIGH ISO VALUE
Many photographers hesitate to use a high ISO setting because of the noise it produces. There are times, however, when you’ll have no choice but to increase it. Sometimes it’s better to have a grainy photo than no photo at all.
Here are a few situations when you'll need to bump your ISO.
A) Achieving a film Look: Digital cameras do not recreate film grain. Raising your ISO setting can help you bring back that analog feeling.
B) Lifestyle Photography: If there’s not enough natural light and you didn’t pack your lights, a high ISO can save you while shooting at your client’s home.
C) Sports Events: Using a High ISO will allow you to use a fast shutter speed to freeze motion.
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D) Indoor Birthday Parties: If you use a tripod, you may get away using a low ISO setting with a slow shutter speed. Using a tripod at events like children's birthday parties, however, may be more of a challenge than it's worth. This is one situation where increasing your ISO setting may be the best idea. Kids move fast.
E) No flash allowed: Many places, such as museums, cathedrals and art galleries, will not allow you to use a flash. In these settings, you may have to push your ISO setting up into the 1600 - 3200 range or higher. Remember, grainy photos can help you achieve a moody effect and you can remove unwanted noise later with editing software.
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