Can anyone explain "noise" ?

[cmM]

What is it? Why does it happen? When I say noise talking about pictures am I talking about the sensor being susceptible to electro-magnetic interferences, just like when I talk about noise in a UTP cable, or a radio signal ? Or is it something completely different.

I'm really curious about this.

[Digital Prophet]

Well since I assume that you already know how noise correllates to film grain all I can say is that I was once told that the noise in a digital sensor was caused by the increased power the sensor draws to increase light sensitivity. That power creates a electromagnetic feild which degreades the sensors ability to perform. But that was something I was told not a fact I read.

But the real question is:

I a photo is taken at ISO 1600 in a forest and noone is there to see, does it make noise?

I crack me up.

- Digital Prophet -

[Jon]

Yep - basically all the other EMI around, when you've got a really weak signal from the photocell, can have a disproportionate effect over what it can do to a photocell with a good, strong signal. And minor differences in the individual cells in the CCD/CMOS combined with slightly different signal paths can give a random noise pattern in low signal-strength areas of the sensor.

Think of it like adding a random number between 0-2 to every cell in the picture. Where the light level's already 255, adding 2 isn't going to make much difference. Where the light level's 0, it makes a big difference.

[cmM]

aha

Thanks for clearing that up for me. I was reading about s/n ratios, I just wasn't sure about the "noise"

[Persian-Rice]

Go to you local magazine store and pick up the July/August issue of Digital Photo Pro, they have a great article about noise. How its happens, why it happens and how to avoid it. Very Techincal and informative.

[sGu]

go to dpreview then go to "learn" section, or simply read a in-depth review of any Canon DSLR review, that's how i learned my understanding of noise

[Jmurman]

But the real question is:

I a photo is taken at ISO 1600 in a forest and noone is there to see, does it make noise?

I crack me up.

- Digital Prophet -

:lol: :lol: :lol: :lol: