Film with a rating of ISO 200 needs half as much light to form a good image as does film rated at ISO 400.
Is there a mistake in this sentence, or does "higher ISO" means lower number, or am I not awake yet to comment on technical matters?
Great tutorial, BTW. Helps clarify my misformed notions that came from a physics rather than photography viewpoint. Un roi sans divertissement est un homme plein de misères
For a film camera, a bright day would use ISO 100. An overcast day would use ISO 400 which needs less light to capture a photo with.
With digital you can get very large ISO numbers for night shots and very low light but it does get very grainy eg at ISO 1600. Ad astra per aspera
