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Old May 25th, 2004, 12:53 PM   #1
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ISO Ratings?

Hi guys...

Just got done checking out Wayne Orr's suggestion for documentarians and am wondering just what are ISO Ratings?

I checked through a search of this forum... didn't really say very much. I checked the 'net via Google and other engines. That didn't help either!

Also, do ISO Ratings even apply to the VX2000?

Thanks in advance, Linda
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Old May 25th, 2004, 01:15 PM   #2
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ISO (International Standards Organization) is the term applied to the speed or sensitivity of film. In the old days it was referred to as the films ASA or you may just know it as film speed (100, 200, 400, etc.). In most instances film behaves during normal exposure (say from 1 second to 1/10,000 of a second) in a linear fashion. A change in the value of light result in an arithmetical change in exposure.

The CCD's in a video camera respond in a linear fashion also. But the RAW data off the chip needs to be processed and an "S" curve is applied to the data. This "S" curve changes the apparent linear response. What does all this mean? In bright light your camera may have an effective ISO rating of between 300 and 400 ISO. However, in low light the ISO may change (due to the non-linear response) to say 500 to 800 ISO.
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Old May 25th, 2004, 01:20 PM   #3
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Thanks loads, Jeff...

I figured it was similar to ASA (I remember that from my Commercial Photography classes). I also remember that the higher the ASA, the grainier the results.

I'll have to check this out and see if I can find out more.
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Old May 25th, 2004, 01:26 PM   #4
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When you increase the gain (gain increases noise, which is the video equivalent of grain) you are increasing the ISO as in the examples on the link you referred to in your post.
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