by Taylor Lloyd
We have come down to our final main element as far as the exposure triangle is concerned and that is something called ISO, which stands for the International Organization for Standardization. Now to the layman, this definition means pretty much nothing so I came up with my own: ISO is a tool on your camera that measures the sensitivity of light coming through the lens and onto your image sensor.
This tool is controlled on the camera itself, either buried under menu settings or simply as a button on the back of your camera. On my little Canon (Rebel T2i/ 550D for all you big time nerds, myself being included) the ISO is controlled on the settings labeled Automatic Depth of Field, Manual, Aperture Priority, Shutter Priority, and Program(A-DEP, M, AV, TV, and P respectively). My camera also has an exterior button for quick adjustments.
Getting back to my previous articles you’ll remember that the aperture is like windows in your house, letting a certain amount of light inside. Shutter speed is like the shutters on your windows, it controls the amount of time the shutters are open to allow the light to enter in through the aperture and onto your sensor. But ISO is like imagining yourself inside the house and you are wearing sunglasses. Your eyes would become desensitized to the light that was entering into the house, which would be like a low ISO number. Confused yet? I’ll try to break it down some more.
ISO is measured in numbers and the lower the number is, the less sensitive your sensor will be to light and vise versa. Depending on your digital camera model, you may have ISO settings in the range of 50 to 6400 and higher.
Higher ISO settings are generally used in darker situations or if you wanted a faster shutter speed but have poor lighting. For example if you are at an indoor sporting event, like a basketball game, where the lighting is poor but you wanted to get crisp action shots, you would have to have a fast shutter speed but in increasing the shutter speed (taking a shorter exposure), you will limit the amount of light coming into your camera. You can compensate for this by increasing the sensor’s sensitivity to light (raising the ISO number), brightening up the image, thus making you able to shoot at a faster shutter speed. But in increasing the ISO you may end up with a grainy or “noisy” shot.
Camera noise is a term to describe visual distortion in your images. In the case of ISO, it is a similar effect as “grain” is in film photography. But unlike film, in which grains are randomly distributed and have size variation, digital noise pixels are the same size and are arranged in a grid, hence making digital noise usually less appealing than film grain. Distortion can be caused by many factors, but one of the main ones is having too high of an ISO setting and this is more pronounced in low light conditions.
With this being said, it is usually a good idea to have as low of an ISO as possible. But keep in mind that if you raise your ISO, it will give you the ability to capture a higher quality photograph in less than favorable situations where the lighting is poor and/or there is action involved because it gives you the ability to use a faster shutter speed and smaller aperture (a large F stop number) to get a sharper scene. Some examples where this may come in handy include indoor sporting events or concerts, art galleries, churches, night photography, and even birthday parties where blowing out candles in a dark room would be ruined by a flash.
After covering the three main aspects of the exposure triangle, I hope I have shed some light (no pun intended) on how these elements work individually. Putting these components together on the other hand, is a whole different topic that I may delve into in a future article but until then, happy shooting!