In the generation of digital photography, some terms have differed from their film days. The definition of ISO is one of them, having a different need in film photography. So what is ISO? In film, camera ISO used to refer to the light sensitivity of the type of film. The higher the ISO numbers on the film, the high its sensitivity to light. So if you plan to shoot in a dark area, go for the film number with the higher ISO.
If that’s for film, what is ISO for digital cameras? It’s still relatively the same. The lower the ISO setting, the lower is its sensitivity to available light. With the higher ISO setting, pictures tend to become grainy because of the amount of light the sensor can process. You can look at other examples online for image samples for ISO settings. Cameras nowadays can have an ISO as far as 3400 or even higher, but you can compare that lower settings can give less graininess or noise in a photograph.
For example, what is ISO 800 compared to ISO 100? ISO 100 is the standard ISO setting used for natural lighting and it would give you a more detailed shot of your subject. Try it, you’d be able to see all the lines clearly and the effect is a mix of light and shadow. However, with ISO 800, you can probably see that the subject with more light on it, however, if you peer in closer, it would have more grains an noise and some of the details would not be visible any longer. You can compensate to remove the noise in post-processing, but there’s only so much a computer can do over getting the proper setting on your camera.
Your ISO setting is one of the most important details you should know when understanding your camera. You can put your ISO setting on automatic for your camera to choose the best setting, but more often than not, a camera will choose the lowest desirable that it can meter. So learn how your camera works and do not be afraid to try different settings to know what works in what setting.