20D noise at ISO 100

[drevil]

Would welcome an opinion on why I am getting noise in low light situations with my 20D at ISO 100. Its

visible in the RAW image.

[drevil]

Here is a crop at 100%

[awindsor]

Are you by any chance using Adobe Camera RAW to develop your image. The chances are that your images are underexposed and being autocorrected by ACR. This correction exacerbates the noise in the image particularly in the shadows.

 

Check out

 

http://www.luminous-landscape.com/tutorials/cr-auto.shtml

 

This seems to me the most likely.

 

The other possibility is that the colour of the light is causing problems with the Bayer sensor (very different channel exposures) which can cause extreme problems when you try and white balance the image. The only possible remedy for this is a strong colour correction filter. Does setting the WB to daylight alleviate the noise ?

[drevil]

Thanks for that, I think you got it right first time. I went back and reconverted the original

RAW file. WB adjustment made no difference but the exposure was exacerbating the noise in

the shadows. Its much less noisy with the exposure setting turned down.

[awindsor]

I was clutching at straws in case it wasn't the exposure increase. Some lighting can certainly give horrible effects when you try and white balance. It happens with tungsten to a certain degree since the blue channel is the noisiest anyway and to balance tungsten you have to increase the blue channel considerably.

[drevil]

Underwater there is very little in the red and green channels so I think you have a good point.

But the ACR default overcooked the exposure and I didnt turn it down enough the first time.

Thanks for replying because I'd read somewhere that the auto-focus servo can cause image

noise and I thought it might be that. Except I'd shot in one shot mode so I was a bit puzzled.

[gromoslawpirx]

'using Adobe Camera RAW to develop your image' -

that's a good one.

[gnashings]

"develop the image" - I think that's so cute, in a pathetic, wannabe kind of way.

 

Amazing, despite the myths, when you underexpose with a digital it still looks... underexposed... who'd a thunk it.

[awindsor]

"Develop" is standard terminology for RAW conversion, matches Adobe's terminology, and moreover matches the regular English usage.

 

Get a life guys.

 

Peter, the proper film analogy would be that a push processed image still looks push processed.

[steve torelli]

Gromaslaw and Peter - other than posting arrogant and condescending remarks aimed at a long time member, do you have something of value to add to this thread?

[drevil]

Thanks Alistair for replying, it totally answered my question.

[awindsor]

The servo focus issue is really only for high ISO and then only with certain lenses. You shouldn't see an effect at ISO 100.

[jim_mcdonald1]

Sorry to hijack but along Steve's line; I learn loads from scanning these threads and my photography's improved as a direct result. I so much appreciate the time and effort that Alistair and others commit. Your comments are detailed, constructive and civil and I thank Alistair and the rest of you for that.