Raw conversion and demosaicing issues

Started Jun 1, 2011 | Discussions thread
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boggis the cat Veteran Member • Posts: 6,329
Raw conversion and demosaicing issues

In another thread some issues with artefacts from raw conversion were uncovered, so I thought I'd post this as it got buried amongst the "moire" argument.

The start point in the original thread:

Jim Stirling posted some odd-looking results from the E-5 and GH2. The JPEGs of the shots did not show any problems but his raw conversion (from ACR) did.

I tested out RawTherapee on the E-5 sample shot and found that the demosaicing algorithm seems to be a culprit for introducing colour artefacts / "colour moire":

The best algorithm here seems to be "amaze" (the algorithm used is within [] at the end of the filename). This output seems fairly close to the Olympus conversion algorithm / OOC JPEGs, but delivers more detail in some instances.

ACR / Lightroom output seems fairly close to the results using the "vng4" algorithm. It appears that Lightroom is not the best raw conversion option for Olympus.

If you have access to some other software, would you please download the raw file for this shot and process it then post the result. (This is the file named "E5hSLI0100_NR_OFF.ORF", about three-quarters of the way down this page: http://www.imaging-resource.com/PRODS/E5/E5A7.HTM .)

It would be good to know how good or bad the output from different raw conversion software is.

If you know of other settings that affect the production of these sort of false-colour artefacts then please post your findings. (Particularly if you know of a work-around in ACR / Lightroom to prevent this problem, other than disguising the artefacts by manual editing.)

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