ISO vs noise

[bilwor]

In the old days of film an ASA of 400 was grainier than 100. Is this still true in the world of digital, an ISO of 400 is noisier than 100?

[CJPalmer]

Yes. The higher you set the ISO, the more electricity and therefore heat go into the chip. This produces the noise. The other factor is exposure length. A long bulb exposure will also produce more noise, especially at high ISO's. You'll want to experiment with your camera to see how much noise shows up at the different settings. The newer cameras and technology are able to go higher with less noise. Lightroom and photoshop have noise reduction tools.