ISO Settings on your Camera Explained | Digital Photography Tutorial
Understanding ISO settings on your camera. What ISO means and how it affects the photographs you take.
ISO is the term used to describe the sensitivity of film to light, defined by the International Organization for Standardization (ISO).
With film cameras, this ISO rating was used when describing different types of photographic film, from 100 ISO (low sensitivity to light) to 1600 ISO (high sensitivity to light). With digital cameras, the ISO rating has remained, and now refers to the sensitivity of the camera sensor to light.
100 ISO, the standard setting
Most digital cameras come with the ISO set to 100 as standard. This means that the camera will record the best image possible with the least amount of digital noise, at the potential cost of a slower shutter speed. In other words the shutter has to remain open for longer to capture the photo as the camera sensor is at its least sensitive to light.
This becomes a problem in low light or sports photography, as a badly lit or fast moving subject doesn’t allow for the longer shutter speeds required. To compensate for this, some cameras will automatically adjust the ISO setting to make the sensor more sensitive to light, meaning that a faster shutter speed can be used.
The downside of this increase in ISO rating is that the final photo becomes more noisy (grainy) as the sensor becomes more sensitive to light and unable to accurately record each individual pixel element.
Controlling the ISO value
While some cameras will automatically adjust the ISO setting for you, it can sometimes lead to undesirable results, especially if you are striving for the ultimate in image quality. If the camera is tripod mounted and shooting a still subject, ISO should remain at its lowest value possible.
If you can, turn off the auto-ISO option and control the rating manually. This will help you retain control of the amount of noise that will be present in the final photo, but you must ensure the shutter speed is sufficient to stop the subject becoming blurred (either through the subject moving or camera shake.)
The Future of High ISO values
Newer high end DSLR cameras are now extending the ISO rating beyond the 1600 maximum (3200, 6400 and 25600 from the Nikon D3) that has been around for years, as the internal hardware and software gets better and better at controlling the problem of digital noise.
Using a digital camera now offers you the freedom to alter the ISO setting between shots, and not just between films. This means that you can make a judgement call on a ‘per shot’ basis as to what the ISO setting should be for a particular photograph.
Once you understand the concept of adjusting the camera sensitivity to light, and the consequences this has on the final image, you can quickly make alterations and get the best possible photo using the optimum shutter speed vs. digital noise ratio.
Finally, experiment. Try out the different ISO settings while keeping a constant shutter speed to see the effects of your changes. Assess the amount of digital noise you get and at what level you find it acceptable. While sports photography usually benefits from a clean image, sometimes a little film grain can actually add appeal to the final image.