Exposure Part 3: ISO

Hi! ISO is the final part of the Exposure trifecta, the 3 fundamental ways to control the amount of light to get your desired photo. Check out my posts on the other two parts of the Exposure trifecta if you've missed them: Aperture and Shutter Speed. Traditionally, ISO was the level of sensitivity the roll of film is to light. With digital photography, ISO is a measure of how sensitive the sensor is to light. It’s a great tool to capture objects in low light without having to use a tripod. By increasing the ISO, your camera’s sensor is more sensitive to light, thus allowing you to use a faster shutter speed. However, increasing the ISO adds more grain to a photo.

ISO

Effects on Your Photo: ISO allows you to capture images in low light situations without a tripod, or a fast moving object without motion blur, such as this example below during a low light concert:

 Future Islands at the Fillmore Auditorium - Denver, CO.

Future Islands at the Fillmore Auditorium - Denver, CO.

Effects on the Camera: ISO changes the sensitivity of the sensor to light in your camera. See the examples below from a bust of Homer at the Trinity College Library in Dublin, Ireland. The Low ISO photo has less grain than the High ISO photo.

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How it Works: For the most part, your ISO setting will be set to Auto, but you can manually change the ISO as well (See your camera’s instructions). ISO levels usually doubles beginning at 100 and 200, all the way up to 40,000. Each ISO level means the camera’s sensor is twice as sensitive to light as the previous ISO level. For example, a camera at ISO 40,000 is 100 times as sensitive to light than ISO 400. What does this mean? This means it takes 100 times less time to capture an image, thus a faster shutter speed:

 ISO 400, Shutter Speed 1/10s

ISO 400, Shutter Speed 1/10s

 ISO 40,000, Shutter Speed 1/1000s

ISO 40,000, Shutter Speed 1/1000s

 Lower ISO = Less Grain

Lower ISO = Less Grain

 Higher ISO = More Grain

Higher ISO = More Grain

Thanks so much for tuning in! This was the final part of the Exposure trifecta: Aperture, Shutter Speed, and ISO. In normal light situations, I like to keep the ISO as low as possible (around ISO 200) to avoid a grainy photo. However, in low light situations, such as the examples above, I’ll have to turn the ISO up at times in order to capture a photo without too much motion blur. These are the fundamentals of how to control light in your photographs. Be sure to tune into Composition and Lighting to begin taking some awesome pictures!

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