In photography, ISO means the sensitivity of camera sensor. Aperture, Shutter and ISO are three factors of exposure and it is one of them. ISO has the attribute for photographers to shoot in low light conditions. It has the common settings of 100, 200, 400, 800, 1600, 3200, 6400 & 12800 which is also called Hi1. Settings may vary by camera. In higher level camera, it starts from 50 which is very low and produces a best image.
How to change/set ISO in Camera
Since the ISO is the sensitivity of the camera sensor, it indulges camera sensor into sensitivity mode to capture low light image depending on the light conditions where photo is to be taken. Let’s talk about its advantages and disadvantages, also it’s combination with aperture and shutter speed. There’s no need of ISO while shooting in daylight or outdoor photo shoot. It only helps in the evening, night time and indoor shoot. It has big disadvantage while shooting in higher number of ISO, that produces a grainy effect on image while lower the number smooth the picture. Beginner lever photographer sets the camera on “Auto-mode” most of the time which allows the camera to set the Shutter, Aperture and ISO by its own choice or depending on the light condition you’re shooting in. Here’s an sample picture which elaborates you the technique and mechanism behind the lower and the higher ISO setting.
If the ISO is set to 100 only, it will have no grainy effect on image cause camera sensor will be set to 100 which is by default or Standard ISO. Applying ISO at 100 doesn't bring the sensor to it's high sensitivity mode. If you set the it to 3200 or 6400, you will clearly see a large amount of grains appeared in image because the camera sensor was in high sensitivity mode. ISO was set to 3200 or 6400 that’s why the image doesn’t get darker but grainy. Higher amount of ISO brightens the image but adds a lot of grains to the image while lower amount of ISO can output your image dark in low light but doesn’t adds grains to the image. Usually, when there's good light conditions, ISO should be set to 50 to 100 only. Increasing the ISO in good light condition mode may result in over-exposed picture. But when there's lack of light like in the evening or night, ISO should be set to according (1600, 3200 or 6400).
Combination of ISO with shutter speed has an ability to produce a bright image apart from grains. If you’re shooting a moving object in low light and want to capture it quite well then you need to set the ISO to a higher point like 6400 or 12800 to bright the scenario in camera’s eye. When the image looks bright, you can increase the shutter speed in order to capture the moving object intact. But you still face grainy effect in the image due to higher ISO.