Ok.
We all know what ISO means, or do we? The truth is that ISO probably doesn’t mean what you think it does, and it might be holding you back from getting the most out of your camera.
www.dpreview.com
Citat:
"ISO changes the lightness of the final image but it doesn’t change the fundamental sensitivity of your sensor. Nor is it an indicator of amplification being applied: although many cameras do increase their amplification as you increase the ISO setting, this isn’t always the case.
This may sound like semantic nit-picking, but it causes a lot of misunderstandings. It’s widely thought that the additional noise in high ISO image comes from the ‘background hiss and hum’ of the sensor’s amplifiers. This
feels right: we’ve all heard more noise if we turn up the volume on an audio amplifier. Unfortunately it’s simply not true: most noise actually comes from the light you’re capturing, so it primarily depends on your shutter speed and aperture. "