ISO

ISO is the sensitivity to light. a lower ISO setting makes the sensor less sensitive to light, meaning it either needs more illumination or a longer shutter speed to achieve the correct exposure. a higher ISO setting will make the sensor more sensitive to light and therefore makes the image/video brighter. 

increasing the iso creates more grain or noise, it can also deteriorate the dynamic range which is why you tend to keep the iso as low as possible. because having a low iso can make your image darker, you may need to change the shutter speed and aperture to get the right exposure. 

using a fast shutter speed with a high iso can help to prevent motion blur, leaving you with a clear and sharp image/video.

the iso values are: (from lowest to highest)

- ISO 100

- ISO 200

- ISO 400

- ISO 800

- ISO 1600

- ISO 3200

- ISO 6400 

this is a video of the 3 different iso settings in video. we used ISO 100 for the first clip which has no grain or noise. the next clip we used ISO 200 which again has no grain. for the last clip, we increased the ISO to 1600. there is a bit of grain in the last clip as we used a higher iso. we lowered the shutter speed and aperture as the video was slightly over exposed.