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05-11-2012, 08:26 AM   #1
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What is Noise?

Can you explain what "noise" is? I realize it's NOT noise, as in audible noise.... I suspect it has something to do with aberrant pixels, but maybe it can be explained in simple terms so this simpleton can comprehend what it is.

Again, thanks for your help and patience with the novice digital camera guy.
Dewman

05-11-2012, 08:29 AM   #2
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This is a pretty good tutorial.

Digital Camera Image Noise: Concept and Types

QuoteQuote:
"Image noise" is the digital equivalent of film grain for analogue cameras. Alternatively, one can think of it as analogous to the subtle background hiss you may hear from your audio system at full volume. For digital images, this noise appears as random speckles on an otherwise smooth surface and can significantly degrade image quality. Although noise often detracts from an image, it is sometimes desirable since it can add an old-fashioned, grainy look which is reminiscent of early film. Some noise can also increase the apparent sharpness of an image. Noise increases with the sensitivity setting in the camera, length of the exposure, temperature, and even varies amongst different camera models.
05-11-2012, 08:30 AM   #3
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Noise
05-11-2012, 09:19 AM   #4
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Noisy?

Hello Dewman,
Digital noise is a grainy appearence, as if the photo is one of those sand paintings. Like it's been "stretched" so that the colors (or shades) have been broken down and have tiny spaces between the dots that make up the complete picture.
Usually the result of a high ISO (sensitivity) when the light is too low for a lower setting. The photo doesn't have a rich, smooth depth to it; It's sandy (hence the phrase "grain") from the film era.
Here's a couple of noisy photos from a classic car cruise, taken just at sunset. The first is ISO 1600, the second is ISO 3200. Both were taken with a K-7, DA 16-45 @ f/4.5, zoom setting 45mm.
Hope this helps!
Ron

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05-11-2012, 09:19 AM   #5
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These are pretty good descriptions...

Image noise - Wikipedia, the free encyclopedia
Noise: Digital Imaging: Glossary: Learn: Digital Photography Review

The Cause: Sensor Noise

Each pixel in a camera sensor contains one or more light sensitive photodiodes which convert the incoming light (photons) into an electrical signal which is processed into the color value of the pixel in the final image. If the same pixel would be exposed several times by the same amount of light, the resulting color values would not be identical but have small statistical variations, called "noise". Even without incoming light, the electrical activity of the sensor itself will generate some signal, the equivalent of the background hiss of audio equipment which is switched on without playing any music. This additional signal is "noisy" because it varies per pixel (and over time) and increases with the temperature, and will add to the overall image noise. It is called the "noise floor". The output of a pixel has to be larger than the noise floor in order to be significant (i.e. to be distinguishable from noise).
05-11-2012, 09:21 AM   #6
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Thanks for the replies. A great explanation. It makes sense now, and a very good thing to know. Kinda' like rating Plus-X at 1600 ASA and developing it in warm developer!

Make it a great day!

Dewman
05-11-2012, 09:42 AM   #7
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QuoteOriginally posted by Dewman Quote
Thanks for the replies. A great explanation. It makes sense now, and a very good thing to know. Kinda' like rating Plus-X at 1600 ASA and developing it in warm developer!

Make it a great day!

Dewman
yep, but for some reason in the digital world people want to shoot iso 25600 with the grain of kodachrome 25

Personally I like grain in shots, but digital noise is not as uniform as film grain
05-11-2012, 10:46 AM   #8
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QuoteOriginally posted by eddie1960 Quote
Personally I like grain in shots, but digital noise is not as uniform as film grain
Film grain can be emulated in PP (post-production editing) with various plugins & warez. Digital noise can be minimized in PP, smoothed a bit, but with some loss of image detail. Digital noise can also be exploited, as by shooting in high-contrast B&W where it lends a 'dramatic' touch to the pic. Yeah, B&W noise is 'artistic' whilst color noise is just crappy.

05-11-2012, 10:51 AM   #9
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QuoteOriginally posted by eddie1960 Quote
yep, but for some reason in the digital world people want to shoot iso 25600 with the grain of kodachrome 25

Personally I like grain in shots, but digital noise is not as uniform as film grain
I would disagree

Digital noise is much more uniform than film grain. the film grains are somewhat regularly sized but irregularly shaped crystals, Noise on the other hand is based largely on the very regularly shaped pixels with different illumination.

but any way, the idea is that the amount of grain / noise is related directly to the film speed shot or ISO set.
05-11-2012, 11:04 AM   #10
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I've updated your thread title from:

"Another question from the new guy" to "What is noise"

This will make it easier for others to find your thread and post their thoughts

Adam
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