ISO and Speed in Photography

The ISO rating of a digital camera refers to the sensor’s sensitivity to light at the most basic level. Just as the case with shutter speed and aperture, the ISO numbers follow the measurements of full stops, meaning that the light sensitivity doubles as the ISO number doubles. Larger ISO numbers translate into a faster sensor in a digital camera; it takes a smaller amount of light to result in a correctly-exposed image. Higher ISO settings generally yield better results when shooting indoors in dimmer light. Digital cameras allow for more flexibility with ISO settings that can be changed in the camera’s internal menu options. The film cameras of the past limited the photographer to selecting one film roll with one specific ISO rating at a time.

“ISO” is an abbreviation for International Standards Organization, and it is one of the most common light sensor ratings found today. Other rating systems include the exposure index (EI) and the American Standards Association (ASA). The most frequently-found ISO numbers range from 100 to 1600 on the standard manually-controlled digital camera that is suitable for beginner to serious amateur photographers. Some higher-end advanced digital cameras have a wider range of ISO settings such as 60-80 at the low end and 3200 or even 6400 at the high end. These are generally used for professional specialty photographic work.

Lower ISO settings work the best for bright outdoor lighting or for shooting images with a slower shutter speed. Determining which ISO speed is the best one can sometimes be a tricky situation due to the common issue of digital noise. Higher ISO ratings increase the rate of data collection in the camera’s sensor, and this often creates higher numbers of unwanted pixels in the resulting image. The most ideal ISO is usually the one that is the lowest possible while still allowing for a clear, correctly-exposed image.

Digital noise and excess pixilation result from obvious image pixels that are not related to the rest of the subject matter. They are frequently too bright and can often appear as a range of scattered rainbow colors that are especially obvious against areas of the image that are overexposed. A high ISO with a long exposure can increase the digital noise even more, and this usually results from the use of an aperture that is one or two increments too small. Trying different aperture openings is one way to compare which results have the lowest amounts of pixilation.

Faster ISO settings can capture a better-lit image in dimmer light, and the problem of digital noise is often a trade-off that can be minimized with some practice and experimentation with different settings. Some digital single lens reflex cameras come with a mechanism for reducing the most noticeable of extra pixels. A quality image editing program can also correct some of the excess digital noise, but this option is one that should only be used as a secondary one. Correct ISO settings during shooting should be the ideal goal for clear and well-lit images.