ISOs?

[jkitzman]

Can anyone point me to a good online explanation of what ISO settings do, and generally when to adjust them? (Or provide an explanation :)

Thanks much!

Jacob Kitzman

[mpkirby]

THe higher the ISO setting, the more sensitive the CCD is to light. How much more is defined by ISO (and I'm not exactly sure of the technical definition. ) I believe that ISO 100 is twice as sensitive as ISO 50, and ISO 200, is twice as sensitive as ISO 100.

The sensitivity corresponds to aperture size and shutter speed (for typical cameras). So if you have a well exposed image at 1/30 at f8.0 with ISO 50, you can vary the variables, and maintain a proper exposure. So for example, I could move from 1/30 to 1/60, and increase my aperture from f8.0 to f5.6. That would allow the same amount of light against the CCD.

Changing the ISO works the same way. If I have a well exposed image at 1/30, f8.0, ISO 50, I could increase the shutter speed (to reduce blur) to 1/125 (2 stops). I could then either open my aperture more, or I could increase the sensitivity of the CCD from ISO 50 to ISO 200.

A couple of caveats. The G1 does support ( I believe) half-stop in some of the shutter speeds and aperture settings. So you should look up in a good photography book the specific numbers. The other caveat, is that ISO 50 on the G1, is not really ISO 50. I don't know if they maintain consistency up the scale or not. (for example, ISO 50, may really be ISO 65, but ISO 100 is definately ISO 130).

Experiment, and let us know!

Mike