What is ISO?

I decided to investigate the function of ISO as its merely an abbreviation to me at the moment! I will study its features and process and hopefully arrive at some test images taken by myself to prove I have learnt from this subject.

ISO stands for "International Organization for Standardization"

ISO sensitivity expresses the speed of photographic negative materials.

What ISO denotes is how sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations.

ISO (equivalent) speed on a digital camera gives an indication of the sensitivity of the image sensor.
The best image quality is usually obtained at the lowest ISO setting on your digital camera.
If by adjusting the shutter speed / aperture combinations you cannot obtain a correctly exposed picture (usually in low-light situations), then you may want to select the next higher ISO.
However, remember that using a higher ISO usually results in noisy images on consumer digital cameras.
Use a high ISO if it is a choice between missing a picture and being able to capture an image -- even if it means you need to spend time cleaning out the noise in post-processing using a noise reduction software.
If you leave your camera on "Auto ISO" and if you find that most of your images are noisy, then perhaps you are taking most of your pictures in low-light situations where the camera has automatically selected a higher ISO.
If you are printing mostly 4x6 in., you may find the noise is not evident in the prints (and so you don't need to worry about noise at high ISO) though they may be visible at original sizes on screen.

I shall shortly demonstrate the term ISO by practising taking images with different ISO settings in a future blog.