All About Sensitivity and ISO

All About Sensitivity and ISO

ISO is a very important setting on your camera that highly affects image quality. ISO stands for International Standards Organization, and it is a standardized scale for measuring sensitivity to light. When taking a picture, your ISO setting is used to determine how sensitive your camera is to light. It is one of the 3 settings you need to understand in order to take a quality photograph manually. ISO adjusts the sensitivity of the digital image sensor inside your DSLR camera. The responsibility of the image sensor is to gather light and transform it into an image.

It is important to understand that the LOWER the ISO number (100, 200, 400), the less sensitive your camera is to light, and the HIGHER the ISO number (1600, 3200), the more sensitive it is to light. The ISO setting you decide to use will depend on the amount of light in the setting you are taking pictures in. Therefore, if you want to take a photograph indoors or at night when the light is dim, you must set your ISO higher in order to produce an image. And vice versa, when taking a photo outdoors in daylight or in other bright scenarios, ISO needs to be lower in order to produce an image. In other words, the more light you are working with, the lower you can set your ISO.

However, you must know the risks that come with a higher ISO setting. Increasing the ISO, while often necessary in cases of low light, or fast shutter speed, comes with certain setbacks. As you raise the ISO, more light registers on the camera’s digital sensor. The more easily light is registered on the sensor, the more likely the light coming in is to distort, which can lead to grainy images, and skewed coloration. For this reason, you typically want to keep ISO as low as possible. To produce clear images, photographers will set their cameras to a typical ISO based off of the light in the setting and adjust the shutter speed and aperture however they prefer. Bottom line, there is a specific ISO that will always be best for specific settings and it is important for a photographer to understand how to use it.

High ISO:

Notice that the image has a lot of noise, with occasional colored pixels in the black sections. However, this image was shot at night, with low light. Increasing the ISO may have been the only way to achieve proper exposure. And the result is not altogether undesirable, depending on the artist’s preferred aesthetics.

Low ISO example:

This image was shot outdoors in bright daylight. The photographer therefore had no problem shooting a properly exposed photograph with very low ISO. The low ISO means that the image comes out very clean, with absolutely no graininess.

Varying ISO example:


This image was shot with four different ISO settings and then composited to show the differences as ISO changes. At 100 ISO (typically the lowest setting) the image is crisp and devoid of grain. The image is progressively less sharp as the ISO moves up. At 3200, the image is grainy with slightly muddled colors.