Road Train !!!!!!!!!!

by Russell McMahon

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I have been told that this photo has terrible noise.
I wasn't aware of this fact! :redface:

Morning scene, F4.8, Shutter: 1/50, ISO 100, Focal 14.4mm.

The fog was dense of course, but still it wasn't "too" dark.
Canon Powershot SX210 IS

Why is there too much noise in a fog photograph? Small sensor - the culprit?

enter image description here

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what is the final file size of this iamge? –  Graeme Hutchison Jan 16 '12 at 12:20
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There seems to be quite a lot of artefacts in the fog (which may simply be the scene through the fog). I think this is emphasized by there not being anything in the scene that is particularly clear. The branch at the top is the closest to non-fogged and that hints at but lacks colour suggesting it could be underexposed? Having a longer exposure may have smoothed the fog effect to reduce the artefacts (or made them worse and if it was moving it would certainly have blurred the car). You may want to take a look at: cambridgeincolour.com/tutorials/fog-photography.htm –  forsvarir Jan 16 '12 at 12:47
    
@forsvarir What is artefact? –  TheIndependentAquarius Jan 16 '12 at 15:22
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@mattdm thanks for the linked threads. –  TheIndependentAquarius Feb 20 '12 at 11:59

3 Answers 3

up vote 6 down vote accepted

I am fairly certain what people are telling you is "noise" are actually JPEG compression artifacts. Unlike RAW images, JPEG images use a form of lossy compression...that means that some degree of detail and perfection in an image is permanently lost when saving a JPEG image. From what I can tell, the photo you posted is not noisy at all, however it does display a fair amount of mild JPEG artifacting and a little bit of banding (usually called posterization) in the bottom portion.

This is a pretty normal consequence of JPEG compression with low-contrast scenes and smooth gradients. JPEG compression is excellent when there is a lot of detail, however it tends to degrade quality pretty quickly when there is a minimal amount of detail, and does quite poorly with smooth gradients. Your photo has both a low amount of detail (by design...its a photo of fog, after all), and has a fairly smooth gradient from top to bottom. You may have been able to avoid the artifacts and posterization if you had used a lower level of compression (higher JPEG "quality"), but to fully eliminate all the negatives, you would have had to have used one of the top two JPEG quality settings, which pretty much eliminates any space savings gains.

If you want to avoid the quality issues with JPEG, you should use RAW if you can. Whenever you save a JPEG, from RAW or anything else, you should try to keep the quality setting around 70-80 (or "high"), as that will usually produce some useful space saving without degrading quality too much.

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Thanks for telling the new term. –  TheIndependentAquarius Feb 20 '12 at 11:56

I can't see any obvious noise in the photo at this resolution. I can see some JPEG artifacts (sections where the subtle differences in shade look like blocks rather than a gradual transition). Some people get confused between "noise" and "artifacting", and refer to both as "noise".

Actual noise exists in almost all digital photos to some extent. Cameras with smaller sensors are more likely to make an image with some noise than a larger sensor under the same conditions.

You mention in the 1x comments that you boosted the contrast. This is likely to make any noise that exists more noticable.

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I agree. I see artifacting almost covering the area below the car headlights. I don't think you need to worry about the noise in this image, as it was shot at ISO 100. For a critique, the amount of noise(if any) is not a major concern here. –  dpollitt Jan 16 '12 at 14:16
    
Thanks for replying. –  TheIndependentAquarius Feb 20 '12 at 11:57

Is it noisy? What would a noiseless photograph of fog look like anyway? On my 27" iMac this image looks like a foggy scene.

Unless the judgement based on a larger, higher resolution image which displays noise, e.g. coloured pixels, I would disregard the opinion.

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they are all saying it is all noisy ! 1x.com/#!/forum/photo-critique/30891 –  TheIndependentAquarius Jan 16 '12 at 12:07
    
1x.com does not tolerate idiots so I assume they have their reasons and would ask for clarification of what they specifically regard as noise. Fog is not uniformly dense and I still think this looks like fog. Nice pic BTW. –  epo Jan 16 '12 at 14:20
    
1x.com does not tolerate idiots You are referring to me as an idiot? Ever thought of minding your language? –  TheIndependentAquarius Jan 16 '12 at 14:30
    
@Anisha: epo is saying that the people on 1x.com must not be idiots, not that anyone is. However, I think that's giving way too much credit. I think the commenters there just don't know what they're talking about, and it wouldn't be the first time. –  mattdm Jan 16 '12 at 15:13
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@Anisha, sorry, the comment got too old and I couldn't edit it. I meant that 1x does not tolerate idiots so they must have a non-idiotic reason for expressing such an opinion so it might help to ask them what exactly they meant. EDIT but to echo mattdm, in this case I do not think they know what they are talking about. –  epo Jan 16 '12 at 16:37

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