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Old Jun 16, 2006, 11:17 PM   #1
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just going through reviews and whatnot... i found something about ISO and dont understand what they mean? it says "Sensitivity:100 to 800 (ISO equivalent); HI-0.3, HI-0.5, HI-0.7, HI-1 and HI-2 available" what does the
HI-0.3, HI-0.5, HI-0.7, HI-1 and HI-2 available

no big deal just curious.

thanks in advance

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Old Jun 17, 2006, 12:04 AM   #2
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I never noticed it before, so I got curious. But it looks like "HI-1" is set to high ISO (1600 or 3200, depending on the camera), probably just to make it clear to "EXPECT NOISE! I HOPE YOU KNOW WHAT YOU'RE DOING! MAY GOD HELP YOU!" (or something like that)

HI-2 is one full stop above Hi-1. while the decimal values are a fraction (1/3 or so) stops below HI-1.

Just my conclusions from what I've gathered.

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Old Jun 17, 2006, 7:00 AM   #3
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Digital Camera Sensors are analog devices. When light hits the photosites on a sensor, they generate a signal.

When you increase ISO speed, the camera is amplifying that analog signal, prior to the analog to digital converter in most cases.

But, for "Extended" ISO modes (or "ISO Boost" modes), what tends to happen is that the values generated by the photosites are multiplied after the Analog to Digital Converter (they only amplify them so far prior to that). ISO 3200 is an "Extended" mode in most models that have it available.

In some models (for example, the Nikon D200), the Extended ISO speeds can be increased in smaller increments, so that you don't need to go straight from 1600 to 3200. D200 ISO speeds:

HI 0.3 = ISO 2000
HI 0.5 = ISO 2200
HI 0.7 = ISO 2500
HI 1.0 = ISO 3200

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