What is ISO? Photography Tutorial: ISO Made Easy
Simon Walter
ISO controls graininess/noise. The lower the ISO, the less graininess. Graininess for artisitc effect can be added in post-processing, so I would always try to keep ISO as low as possible to go for as sharp an image as poss.
Davi DePaula
I really love all of your videos. Thank you for sharing your talent with us. Your explanation of ISO is very good, specially for beginners to understand, but your analogy is off. ISO doesn't increase sensor sensitivity, ISO is applied gain. When you change ISO, you are changing how much gain your camera will apply to the image after it is captured by the sensor and not changing the ability of the sensor to capture light. Anyways, I love your videos.
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