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04/03/2003 11:07:47 PM · #1 |
How does the ISO work in a digital camera? Does it actually do something different? Does the CCD records color in a different way in each setting?
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04/03/2003 11:22:21 PM · #2 |
Hi Jenarom,
I believe it is purely a sensitivity setting for the CCD. It simulates the sensitivity of film. Similar to film, a lower ISO setting will mean less grain in a digital image (particularly with long exposures at night).
Andrew |
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04/04/2003 10:00:28 AM · #3 |
Think of it as a volume control - turn it up high and you can take pictures in lower light, but there is more of a tendency to distort (noise on the picture)
Have it low and you get all the sensitivity but only when the light is good.
Exposure is basically just the combination of 3 things :
Shutter speed, aperture size and ISO sensitivity. One of the great things about digital over film is that you have much greater control over ISO, being able to change it on a shot by shot basis, rather than roll by roll.
Double the ISO and you can half the shutter speed for the same exposure, and that kind of thing. Some digital cameras handle the noise better than others however. |
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04/04/2003 11:11:40 AM · #4 |
Thanks guys! I know what ISO can do on film, and with the responses you give I understand that in digital cameras the ISO setting actually manipulates the sensitivity of the CCD. Right?
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04/04/2003 12:56:32 PM · #5 |
That is right. There is however one side-effect and that concerns the dynamic range (dr) of the ccd. Only at certain levels the dr is optimal, that is why on certain camera's the ISO100 or ISO50 can only be used by activating a special menu item.
An example is Canon's EOS 1Ds and 1D. ISO50 resp. ISO100 is only available after activating a custom function.
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04/04/2003 01:26:44 PM · #6 |
It is my understanding that the ISO setting on a D-SLR is equivalent to a gain control. So, as the gain is ramped up, the sensitivity of the CCD is improved. However, the negative side effect of increased gain is noise. Noise in a CCD is like grain artifacts in film.
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