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ISO isn't sensitivity...

Started Jan 23, 2006 | Discussions thread
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Thomas Nilsson
Contributing MemberPosts: 529
ISO isn't sensitivity...
Jan 23, 2006

... any longer.

I've been reading some articles lately and very often the discussion is about ISO sensitivity in digital cameras. But what do they mean by that? (Retoric question;)

In film cameras, ISO is a sensitivity specification of the film and many film cameras are 'informed' in one way or another what ISO the film has in order to make the automatic functions work properly.

However, I'd like to stik my chin out and say

  • In digital cameras, there is no such thing as ISO sensitivity!

There is of course 'sensor sensitivity' which differ from one sensor type to another. But it is always the same for one and the same camera (until we see cameras with exchangeable sensors). Hence, changing ISO sensitivity on a digital like we did on film, just isn't possible.

Still we do have ISO settings on our digitals, and the function is basically mandatory. We all know how to use it and what to use it for, and it is really useful. And many of us knows how it works too. On a digital, ISO is an amplification factor, not a sensitivity.

IMHO, if we stopped saying "increase the ISO sensitivity" and started saying "increase the ISO amplification" things would be a lot clearer to most people, and giving those who don't quite know how it works inside the camera a hint on what is actually going on. For instance, understanding about noise and why it increases when going to a higher ISO amplification would be more intuitive. And on top of that, we'd all be more correct when expressing ourselves


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