What is ISO? - Learning the Exposure Triangle

At Kindred Photography Workshop we make learning manual mode easy and fun.  Manual mode is technical in nature and we try to teach concepts at Kindred in a way that help attendees grasp new information easily.

The first concept we teach is how to get the proper exposure for your photograph, meaning that the image that isn't too bright or too dark.  We call this concept the "exposure triangle" because there are three components of exposure:

1. Aperture

2. ISO

3. Shutter Speed

Last week we posted on Aperture (here). This week we will focus on ISO.  

ISO (International Standards Organization) is the level of sensitivity your camera's sensor has to light. Your camera's sensor is basically the part of your camera that takes available light and transforms it into an image. 

ISO is measured on a number scale typically starting with 50 or 100. ISO sensitivity increases in increments by the power of two, meaning each step essentially doubles the camera's sensitivity to available light (refer to graphic below). The LOWER the number, the LESS sensitive it is to light. The HIGHER the number, the MORE sensitive it is to light. 

Image via google

Image via google

Tulsa Kindred Workshop attendees practicing with the ISO scale

Tulsa Kindred Workshop attendees practicing with the ISO scale

Another way to phrase it is in terms of the lighting in the environment where you are shooting.

If you are shooting in a particular location with less light, say inside or at dusk, you will need a higher ISO number in order to allow your camera to take advantage of as much available light as possible and not produce an underexposed (too dark) image. 

If you are shooting in a particular location with more light, say next to a window or outside on a sunny day, you will need a lower ISO number in order to make sure your photo is not overexposed (too bright).

In order to get a crisp, properly exposed picture, you want to shoot on the lowest ISO number possible in any setting. This will help you avoid a "noisy", or grainy photo.

Tulsa Kindred Workshop attendees finding the correct exposure in manual mode

Tulsa Kindred Workshop attendees finding the correct exposure in manual mode

Combined with the other two aspects of the exposure triangle (aperture and shutter speed), the lowest ISO number that gives your camera the correct sensitivity to available light will give you an image with the proper exposure and a clear, crisp image with no noise.

Terms like light sensitivity, noise, overexposed and underexposed will be covered more in depth at Kindred Photography Workshop, where attendees get lots of hands-on practice using the ISO scale.

Stay tuned for next week's post on shutter speed!