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Old Mar 7, 2003, 11:35 PM   #1
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Default How come noise increases when exposure time increases

How come noise increases when exposure time increases?

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Old Mar 8, 2003, 3:46 AM   #2
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The nature of the beast!

As the CCD is taking the picture it heats up, and after a while the heat effects the pixels, and you get noise.
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Old Mar 8, 2003, 8:38 AM   #3
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It's called a dynamic range thingy :lol: :lol: :lol:

You try to accumulate a tiny signal to a useable level, hence the noise floor with it... This also happen with film when pushed below its ISO/ASA range.

In another word when a signal amplitude is indistinguishable from the noise, that's what one get! The CCD is designed to capture much stronger light... one can design a better CCD for low light, but then it'll be blinded by sunlight ops: ops: ops:
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Old Mar 8, 2003, 10:46 AM   #4
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Thanks guys,
I have been learning alot about cameras from these boards.
Seems like every question I ask someone has an answer

Peace...

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Old Mar 8, 2003, 12:28 PM   #5
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Quote:
Originally Posted by shiggy
Seems like every question I ask someone has an answer
And sometimes the answer has something to do with the question.
_______
I'll even offer the way I view noise and exposure time.


The amount of noise (akin to static on AM radio) is roughly constant* so the amount you get accumulates over time. The longer the time, the more noise. I suspect that the amount of noise increases as the square root of the time of the exposure, e.g., if the exposure time is increased by a factor of four, the noise will increase by a factor of two.

* not really constant - it is very much temerature dependant. So there should be less noise oudoors on a winter day. Also as the camera is used, there will be some heating - that's where most of the energy used by your batteries goes. So you can expect more noise in the last photo in a series than in the earlier ones.
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Old Mar 8, 2003, 10:21 PM   #6
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I sure hope we are all talking about low light here...

I sure don't see any noises when I increase my shutter time from 1/500s to 1/125s :lol: :lol: :lol:

Whoa... a lot of heat generated from those star lights too :lol: :lol: :lol:

Poor Shiggy !!!
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Old Mar 8, 2003, 10:23 PM   #7
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System hiccup just cancel the double posting... Sorry!
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Old Mar 8, 2003, 10:26 PM   #8
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Hehe,
:lol:
NHL= da man

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