Wednesday, July 15, 2009

GMIC for GIMP is not a Gimmick

I've been experimenting with GMIC for GIMP to manage noise reduction. I was taking some photographs of the kids at an indoor swimming pool, and the conditions were pretty harsh. In general, I don't like to shoot above 1600 ISO, but I had to push the ISO to 4000 on a few photos.

Needless to say, the noise was pretty bad, so spent some time trying to tweak the noise reduction. I shot cRAW on my A700, and then used Image Data LightBox and Image Data Converter to get White Balance and exposure set, and then I exported to tiff. I then used Image Data Converter's built in noise reduction (from the RAW file) and GMIC to compare noise reduction.

GMIC has two methods for noise reduction (both of which are documented here). I used the patch-based method, since I don't mind the luminance noise. It also had less settings that were easier to understand.

GMIC seemed to do very well, although it was slow. On a 12 megapixel image, it was taking 15 minutes to do 5 passes, with patch size of 5. With a patch size of 10, it would take over an hour. Because of the time involved, I also played around with the command line for GMIC, to see if I could script out an entire directory to process overnight, but I had some trouble with that (I'll detail in another post). Update: command line issue explained here.

Here's a side-by-side of the results. Overall, I'm happy with the results and it will do in a pinch, but it is just too slow for regular workflow. Either choice works well for smaller prints and is much better that anything I've shot on point-and-shoot digicams.

Original Crop (no noise reduction, shot at ISO 4000 on A700):

Noise Reduction using Image Data Converter (Sony's RAW software):

Noise Reduction using GMIC plugin for GIMP:

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