JPEG Artifacts

[crob2go]

Hello, my question is this: I was shooting a day time scene with my ISO set at

400. Why did photo have noticalbe artifacts? I'm using a Sony f-828 is this is

a factor. My thought is that the ISO may have been to sensitive for the

lighting conditions. Yes/No? Any input would be appreciated......C-Rob

[ronald_moravec1]

You are probably looking at noise from high iso, not atrifacts. Noise looks like spots or sand some of which may be multicolored which is chromatic noise. Luminesence noise looks similar, but is not multicolored.

 

There are noise reduction programs sold to lessen the noise.

 

 

Artifacts appear when you repeatingly open, change and resave JPEGs. The compressing and uncompressing does it.

[rainer_t]

-- "Why did photo have noticalbe artifacts?"

 

Without a sample, its hard to tell what it really is ... but my guess would is, you see high-iso noise (rather than compression artefacts) in your images.

[obakesan]

Hi

 

perhaps its the same thing as I discuss here

 

http://home.people.net.au/~cjeastwd/digital/inCameraArtifacts.html

[peterblaise]

Craig,

 

JPG is a publishing output file format that is inappropriate for original image capture, especially since it defaults to an all-purpose algorithm for JPG encoding for all images regardless of differences between complex and simple, flat or dynamic subjects, and other differences.

 

Set your camera to RAW for capture, then later convert to JPG using your own choices of individualized settings for each image dependent on output size, sharpening, and any other image adjustment you wish to make for that image for that publishing purpose.

 

Also, of course, with a chip that is 1/16th the size of 35mm film, the signal to noise ratio is rather limited. I use ISO 100 only on my Sony 1/16th chip, and I capture RAW only, and then I have great results enlarging to 17x11" and larger (amazing what a good printer will compensate for!).

 

For me, low light shadow areas from a 1/16th chip have waay more noise than brighter areas of the same image. That non-image information is not from JPGing. That is the limit of the (now ancient) linear CCD capture signal to noise ratio. I use noise reduction software like Neat Image on my picture files if I find that noise overwhelming for my taste.

 

Craig, why not share a 511x pixel 100% 1:1 crop piece from the image in question, and with no additional reduction in JPG compression, and let us see what you are talking about?

[kari v]

Small sensor cameras start losing quality fast at ISO 400. Daytime (good light) actually reduces noise, try shooting at ISO 400 or above in dim light...