Panasonic Lumix G 20mm F1.7 II (H-H020A) - Banding

Started Aug 6, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Correction of Banding Noise with Topaz DeNoise

tsi wrote:

Anders W wrote:

One thing I forgot to ask: Have you tried any other software than Topaz for this purpose? If so, what would you say about their relative advantages/disadvantages? In general, I would be interested in anything you have found out in your search for a "Band Aid", whether by means of your own trials or on the basis of whatever other sources you have consulted.

I have tried Topaz DeNoise as a Lightroom plugin:

http://www.dpreview.com/forums/thread/3532757#forum-post-52061838

Advantages:

- Conservative correction. No severe artefacts observed so far.

- Can be used to correct narrow bands as well as wide band.

- With the 20 / 1.7 the frequency of the bands may change somewhere in the middle of an image. Topaz works well with this kind of banding noise.

Disadvantages:

- Default distortion correction has to be disabled. Topaz seems to estimate the signal amplitude for the entire row. With distortion correction enabled, the bands are curved and the estimate is not reliable. As a result, banding correction is less efficient in the center of an image and much less efficient in the edges. The correction can even increase banding in the edges. Setting distortion = -11 in Lightroom may leave some residual distortion correction. In other raw converters it is possible to turn off distortion correction. This may give a slightly better banding correction with Topaz DeNoise.

It's a pity that the automatic correction of distortion (and lateral CA with Pany lenses on Pany bodies) cannot be turned off with LR for special cases like these (or for diagnostic purposes). But one way of handling it with LR might be to try to undo the correction via the distortion slider (as you suggest), apply the banding correction, export the file as a 16-bit TIFF (for best quality), reimport the TIFF, apply the proper amount of distortion correction again, and finally export it as a jpeg. Suboptimal and messy but perhaps workable.

An alternative strategy to reduce the suboptimality might be try to devise a special LR lens profile for the 20 that undoes the correction in a more faithful manner than the crude slider in the development panel manages and then another profile which applies it again to the TIFF. If I understand things right, you have more than one parameter to play with for distortion correction if you use a profile.

- DeNoise is applied after raw conversion, white balance and gamma curve. I believe that this is the reason why the correction is more efficient in dark shadows than in bright shadows and mid levels.

- Correction is not helpful with color banding. I have tried two images with relative wide color bands (the type discussed before) and one image which has narrow bands caused by the ISO bracketing mode.

- Less efficient with very wide bands. The plugin has a slider "banding width" which is the only adjustable setting. First I thought that you have to set it to the appropriate width of the observed bands. But for narrow and wide bands the strongest effect is seen when the slider is at the maximum position (35). Because I have not had problems with artefacts I leave the slider in this position.

- Not as smooth workflow as with build in functions of Lightroom

- Causes banding in clipped highlights. Artefact can be removed by adjusting highlight clipping levels after the banding correction.

There have been two more software suggestions in the same forum, which may be useful as well:

- Dfine2 as a part of Nok software collection

- G'MIC plugin in Gimp

 Anders W's gear list:Anders W's gear list
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