This is a very simple introduction in ISO.

ISO is very simply put a system for light sensitivity. All new digital SLR cameras have some kind of setting where you can adjust what system to use and how sensitive the camera is to be to light in the viewfinder.

Another word for ISO is film speed, and on modern SLR cameras you most commonly have a range of 100 to 3000 ISO systems, depending on model and price class/quality class of the camera. Lower ISO levels means that the image sensors need more time to produce an image, and this is why lower ISO systems are called slow film. This means that longer shutter speeds are required in order to get sufficient light and to produce an image. At higher ISO levels less light is required in order to produce an image, leading to shorter shutter speeds, hence the term fast film. However, when higher ISO levels are used, the noise in the image will be increased, leading to coarser film grain and decreasing image quality.

Difference in high and low ISO settings

So when to use which ISO adjustment?

It really depends on the equipment and surroundings. If you want to shoot a high-quality picture in the dark you should use a tripod with low ISO settings, in order to avoid blurred images at long shutter-speeds. However, if you don’t have stabilizing equipment in dark surroundings, you should apply high ISO settings in order to shorten the shutter-speed and reduce blurring. In dark surroundings, you could also use a flash, of course, but that is only if the object is near the camera.

Any questions? Use the comment field, and I will come back to you.

I hope that this was somehow informative.

elgvin