Grainy and Noisy - RAW Shooting and Processing - CHDK Forum

Grainy and Noisy

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Grainy and Noisy
« on: 11 / August / 2010, 21:27:12 »
Hello Forum, yet another noob from Pensacola, FL.

 I finally got my SX20 v1.02d to take both CR2 and DNG files. I ran a test of the quality between Super Fine .jpg, and the .dng files. I just can't seem to figure out why the .jpgs look so, so, so much better? The noise in the .dng's is extreme.
I really feel that I have some setting off or wrong. The "bad pix" removal script worked, like 20 times before I could figure how the hell to stop it from auto starting! I did read that the .dng files need to be cleaned up, but I'm at a loss of what photo edit to use first, second and possible 3rd? I don't have photoshop, just some of the freebies around.

 Last, I have read and read the chdk guides, and they contain almost every bit of info regarding what the settings do, but I haven't read one guide that gives a noob the "Best Default Settings" to begin with. For instance I had the choice of having the files end in .crw or .cr2 or begin with img, well for a noob there is no right/wrong answer, there is only ignorance. If I picked the "wrong" value it could set up a string of failures down the line.

Would sombody be a great sport and direct me to a Default Settings Guide or a quick write-up?

« Last Edit: 11 / August / 2010, 23:28:28 by Jimbeamrye »

Re: Grainy and Noisy
« Reply #1 on: 11 / August / 2010, 23:29:05 »
Yes the RAW data from these tiny sensors is horrific. Canon hits them with an image-processing sledgehammer to produce the JPEGs you see.

Don't know how much I can help you as I am a linux user and do not own a copy of Windows. But many RAW decoders are based on the free dcraw code (by Dave Coffin), which will read the DNG files from my Ixus 100/SD780.

Dcraw has a noise-reduction feature (-n command-line option). If I set this at 150 it gives quite good results at ISO100, but possibly still a bit noisier than the Canon output. For comparison I use -n 25 on my DSLR at ISO100.

Unfortunately excessive noise reduction also blurs the image and turns subtle detail to mush. So Canon follow it up with a big dollop of sharpening (probably similar to the 'unsharp mask' function usually found in image processing tools). I use the free Imagemagick for this. See my posts on the SD780 thread in this section for examples.

Google finds several free noise reduction programs, so I suggest you give those a try. Then you can play with colours and contrast, and sharpening should be the last step. I use dcraw for the noise reduction and converting the DNG to a TIFF and Imagemagick for the rest, or Gimp if I want to see what is going on.

Unfortunately you are competing with the designers of Canon's DIGIC, who obviously know their stuff. I like to experiment with panoramas and HDR. Otherwise I probably wouldn't bother.
« Last Edit: 11 / August / 2010, 23:36:00 by ixussuxi »


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