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ISO Noise

Gary66 5 246 England
27 Nov 2012 9:50AM
I have recently viewed a blog by Jestertheclown (Brendan), where he was experimenting with ISO and referred to noise, I have heard this term but to be honest clueless as to what it is, I assume it's not a good thing.
Would appreciate some explanation.
Many thanks.

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Nick_w Plus
10 4.3k 99 England
27 Nov 2012 9:55AM
When you increaae ISO, the image has what appears to be "specs" on. Its caused mainly by the camera amplifying the signal from the sensor to give an image - also by heat from the electronics (more applicable to long exposures). IMHO theres too much made of it - if you print and not just look on the web, you can have quite high noise levels before they become visable in print (due to dot gain, paper etc). Also in black and white it can give atmosphere. Its knowhere near the levels you used to see in the film days - then it was regarded as artistic and desirable !!
miptog 12 3.6k 61 United Kingdom
27 Nov 2012 9:55AM
In simple terms this is where the image looks grainy to varying levels of "graininess", in which extreme cases the image looses a lot of detail. Noise is most apparent in shadow and dark areas of the image. Simple test, in a low light situation take a shot at the lowest iso, and then take the same shot at the highest iso. Compare the two, and you should be able to see the difference in noise.
cameracat 14 8.6k 61 Norfolk Island
27 Nov 2012 10:12AM

Quote:IMHO there's too much made of it

Absolutely spot on Nick.....Smile

Its really the prerogative of the pixel peepers, Or technophiles who don't actually take photographs......Grin
mikehit 8 8.0k 13 United Kingdom
27 Nov 2012 10:18AM
Any electronic circuit has random signals in it and this is passed to the image eletronics creating the noise you are referring to.
In good lighting conditions, the amount noise signal is very very low compared to the signal created by the high amount of light hitting the sensor so you don't see the noise in the picture.
When light is low the noise is the same but amount of signal from the light hitting the sensor is lower in comparison so the noise becomes more apparent.

You can overcome the low light in two ways: you can take the picture at low ISO and 'boost' the signal in post-processing to recover the low-light detail, or you can boost the ISO setting and let the camera do the recovery. In both cases you amplify the noise as well as the light signal.

You can to some extent compare film grain and digitalnoise, but many people say that film grain is more acceptable visually and it has been proposed that digital noise is less random than film grain so is more noticable.
Gaucho 16 2.8k 2 United Kingdom
27 Nov 2012 10:32AM
Sums it up quite well mikehit Smile
puertouk 6 1.1k 17 United Kingdom
27 Nov 2012 10:55AM
The easiest explanation is, the higher the ISO the more noise (specs) you get on your image. Bearing in mind, some cameras are better with higher ISO´s than others. Simple!
Gary66 5 246 England
27 Nov 2012 2:39PM
Thanks for your time everyone.
cheddar-caveman 14 1.1k England
3 Dec 2012 7:33PM
In old "film" days it was called grain! The higher the ISO the faster the film was but the more grain you got in your pictures. In those days there wasn't a lot you could do about it but in today's brilliant digital era there are programs and software which can greatly reduce the noise (grain).
Paul Morgan 17 19.1k 6 England
3 Dec 2012 7:42PM

Quote:In old "film" days it was called grain

But there is still a big difference.

Grain is more visable in the lighter areas, while noise shows more in the darker areas.
cheddar-caveman 14 1.1k England
3 Dec 2012 7:49PM
True, dark grain and white noise!

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