Making use of ISO

I am sure you have seen the term ISO many times even since you first had conventional point and shoot cameras where you use photographic films to capture images. When you purchase a roll of film, you would see an ISO number such as 100, 200, 400, 800, and so on. But what do they mean?

In the simplest definition with regards to digital cameras, ISO is the number representing the digital camera sensors sensitivity to light. A lower ISO number such as 100 means the camera’s sensors are less sensitive to light and a higher ISO number means more sensitivity to light.

In the previous post, I made a mistake by quoting that Exposure = Shutter Speed + Aperture. I soon to realize that ISO also plays an important role and that it does affect the exposure as well. It works hand in hand with shutter speed and aperture. So that makes them to look like having a triangular relationship between ISO, shutter speed and aperture.

ISO speed affects the shutter speed and aperture combinations in order to obtain correct exposure. A high ISO is good for dim light situations or low light condition such as for night photography or during dawn where light sources are limited.

The problem with a low light condition (low ISO) is that you often need a longer exposure time, so you have to set a slower shutter speed or a slower aperture setting to capture a good image. Because of the slower shutter speed, you need to use a tripod to avoid camera shake. You don’t want to distort the image when you shake the camera while the shutter is still opened.

Alternately, higher ISO means the more the sensor will register light energy, but not coming from your subject. As a rule of thumb, low ISO is good for bright situations (many light sources) or when things aren't moving much (static objects). Some digital cameras are pretty good at noise reduction and you can leave the ISO on auto, letting your camera judge which ISO would be best, unless you are trying to be creative and want to get a particular effect. But setting the ISO manually is good (ISO 100 or 200) and adjusting it according to the lighting condition during your photography.

Here’s a video to explain ISO using Nikon D60. Most other DSLRs work on the same concept in relation to this video. [Credits: LarkPhoto]