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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?
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.
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.
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.
