A recent post on our Exposure Control Lesson posed the question, What is ISO? Here’s a more in depth explanation.
What is ISO?
What is the ISO standard and what it means to Photographers
ISO is short for International Organizational Standard. In the photographic world, ISO is most commonly referred to as a film rating system. Think film photography, not the movies :) In terms of film, ISO is used as a rating system to tell you how sensitive the film is to light, or how fast the film is. The lower the ISO number (ie 50) the more time the film needs to be exposed. The faster the ISO film speed, less light is required to take a picture.
What is the Best ISO?
In many situations it is not possible to have a film with low sensitivity. Such situations include those where there is low light and no tripod, or where the motion is very quick such; as in sports photography.
Film ISO vs Digital ISO
If you are using a film camera there is a much better chance that you are already familiar with ISO. When you choose your film you select the ISO.
Digital photographers are not so constrained by a roll of film having one set ISO sensitivity, and can change the ISO sensitivity rather easily. That isn’t to say digital cameras can escape the adverse effects of shooting with higher ISO.
In film, when the ISO is too high, photos tend to appear grainy. The same is true with Digital Cameras instead of being called grainy it’s called noise. The higher the ISO, the the more noisy digital photos appear.
Whether your using film, or a digital camera, ISO speed affects the aperture and shutter speed combinations you can use.
So What is ISO?
ISO is a standard telling you how sensitive your film/digital sensor is to light.
- Higher the ISO, the more sensitive the film/sensor is to light.
- ISO speed affects allowed aperture and shutter speed combinations.
- Higher the ISO, the more grainy or noisy pictures may appear.