Call me stupid, but what the heck is "noise"??

[Mickey Fliers]

What is this "noise" of which all you photogs discuss? Please advise.

 

[jann1033]

I'm sure someone will post a tech correct explanation but it's that speckly grainy stuff you see on some digital pics, usually in the darker areas in higher iso( well at least in my camera that's when i see it) the picture with out the noise looks cleaner so you can use a noise removal program( software) to clean it up

 

[Kelly Grannell]

here are some examples of noisy picture vs clean picture

 

[manning]

Here is a sample of noise

The picture on the upper left is the least noisy progressing to the worst on the lower right

http://www.teco.edu/~albrecht/neuro/html/node83.html

 

[0bli0]

noise is random pixels within your picture. think about it like 'snow' on analogue tv reception (the way it looks).

noise is generally caused when the CCD or CMOS sensor's individual photosites interpret what is received differently than other photosites in the same vacinity, but it can also happen based upon cooler temperature and a few other reasons (like just a random electrical signal). this generally happens more often when the sensitivity is turned up - i.e. higher ISO or on long exposures.

noise is generally not a good thing, however i often add gaussian monochromatic noise to my mono shots to give a feeling of silver grain. like this:

museum station

it was actually a very clean image to begin with

 

[Geoff_M]

There's a great anology to "noise" in the audio world. Turn on your stereo, set the input to "CD", but don't start playing the CD... now crank up the volume on your stereo way up. Instead of hearing nothing, you'll hear a "hissing". That's basically what digital camera "noise" is... except with noise you see the "hiss" as a sort of colored "snow" across the image. The cause in your stereo and digital camera is the same: you're turning up the signal amplifier in each device. Just like you have to turn up the volume on your stereo to hear something that's recorded at a low volume, you have to "turn up" the signal that comes out of your camera's sensor when shooting in low light. Unfortunately, the "noise" also gets amplified.

(0bli0... "Mind The Gap"!)

 

[0bli0]

maybe we should start referring to noise as hiss - coining new terminology here on Dis! 'my camera gets very hissy at 800...'

LOL - the gaps aren't so bad here, although the anti-terrorist patrol gave me major grief: 'why would you want to spend 15 minutes taking photographs of a train station? why do you have all of this equipment with you? why do you have such a large bag with you?...' gmafb... i had a paid ticket and i was not taking the photo for commercial reasons.

back off, man, i'm a photographer... (i actually said that after they had searched my bag, interrogated me, and saw my ticket. besides it's museum station, not central. not very busy at all...)

 

[Geoff_M]

LOL - the gaps aren't so bad here, although the anti-terrorist patrol gave me major grief

The first thought through my head upon seeing that photo, after "Wow, nice shot", was "I wonder if the cops hassled him/her for taking that shot?"

 

[Mickey Fliers]

Thanks all. It really helps to see the examples of noisy to clean. Kelly had posted some pics that she thought were noisy and I thought they looked fine. However, if I had seen a pic that was clean next to it, I would have been able to see the difference. I guess you all have a much more experienced and trained eye.

You are all very helpful.

 

[Amy]

Kelly, thank you for posting all those noisy vs. clean pictures. If one of mine turned out like your noisy pictures, I would have thought mine was just out of focus; I never knew you could clean them up so well.

Is there some trick to identifying what's out of focus vs. noisy? Or is this one of those things that you learn the more pictures you take?

I'm thinking of asking Santa for some photo editing software this year, probably Photoshop Elements 4 or something similar. Will they all remove noise?

You know, I was perfectly happy with my digital pix until I discovered the DIS photography board! Now I want a new camera and photo editing software (I've just been using the stuff that came with my Canon A70). Now I look at every picture and try to figure out what I could do better.......

 

[AZ JazzyJ]

I thought noise was what people older than me called rap music. My grandpa was always asking me what that noise was coming out of my radio. I never thought to take a picture of it.

Jeff

 

[Kelly Grannell]

it'll be easy to distinguish between noise and out of focus.

here's full-frame pic with and without noise. It's easy to distinguish once you know what to see.

 

[Kelly Grannell]

you see the red-green-blue speckles? that's noise. The noise makes things look blurry. That's why I always put emphasis on ISO noise.

 

[Boss Hogg]

I thought noise was what people older than me called rap music.

LOL, couldn't agree more, I guess I must just be getting old!!

The other thing I would say, as 0bil0 mentioned, is that as with everything in photography, noise can be good sometimes. It's all down to taste I guess.

 

[Amy]

Thanks, Kelly! I can see the difference now. Right around the bend of the box, some of the letters are out of focus, which is clearly different than the noise in the 2nd picture.

I guess once my stint on the high school band board is over, I'll be signing up for photography classes at the community college!

 

[AZ JazzyJ]

I guess once my stint on the high school band board is over, I'll be signing up for photography classes at the community college!

Just remember, you can't take pictures with a tuba.

Jeff

 

[Amy]

Just remember, you can't take pictures with a tuba.

I'll bet they cover that the first lesson!