DIGITAL ISO

D
Posted By
Dennis
May 29, 2004
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222
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What physical changes occur in a digital camera to change light sensitivity with a change
in ISO. Does (can) it affect the final image. Any ideas………cheers Dennis
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digital iso

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M
Marsupilami
May 29, 2004
Dennis wrote:
What physical changes occur in a digital camera to change light sensitivity with a change
in ISO. Does (can) it affect the final image. Any ideas………cheers Dennis

Digital cameras have only ONE ISO setting, (most of the time 50 or 100 ISO) higher setting are made with digital improvements (called electrical gain) depends in part also of the sensor size (2/3",1/8" or other) -bigger the size is -better the dynanic range is and less the noise appear. A 2/3" sensor with 3 Mpixels will create less noise with the same one with 5 Mp.
Of course most of the digital cameras are unusable at more than 800 ISO (for the best one)
because of this noise appearing particularly in the shadows of the image (can be partially erased with "noise" filter in PS)

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Don
May 29, 2004
Strictly speaking there is no ISO rating for dital cameras because the International Standards Organization (ISO) hasn’t establish such a standard as yet. The last I heard, they were working on it but had not yet issued a draft.

The ISO rating for film is based on its sensitivity to light relative to its toe characteristics. That makes it difficult to establish a direct relationship to an equivalent ISO rating for digital focal planes because they don’t exhibit a toe. Most manufacturers do claim an ISO for their cameras, though, but since it isn’t standardized there are some differences from one manufacturere to another.

Don

"Dennis" wrote in message
What physical changes occur in a digital camera to change light
sensitivity
with a change
in ISO. Does (can) it affect the final image. Any ideas………cheers Dennis

TT
Tom Thackrey
May 29, 2004
On 29-May-2004, "Dennis" wrote:

What physical changes occur in a digital camera to change light sensitivity
with a change
in ISO. Does (can) it affect the final image. Any ideas………cheers Dennis

ISO is used in film photography as one measure of the sensitivity of the film. DCams have used ISO numbers to indicate the sensitivity of the digital sensor. Increasing the sensitivity is done by increasing the amplification of the signal from the digital sensor. Increased amplification causes increased noise (analogous to increased grain in film.)

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Wilder and Wilder
May 29, 2004
Just imagin having a light dimmer switch on the camera. The more you increase it, the worse the picture gets until it’s unusable.

"Dennis" wrote in message
What physical changes occur in a digital camera to change light
sensitivity
with a change
in ISO. Does (can) it affect the final image. Any ideas………cheers Dennis

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