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What in the world is this?


agreenspan

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Hi. Can anyone please tell me what these rainbow-like maze artifacts are on the shingles in this photo. It only appears on this photo, where the shingles are in focus. I used the M8u Is this moire?

Thanks,

Stephen.

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Yeeeaaah...I am not so sure this is just moire. I would get this in things like backlit water, high contrast areas, lots of places. C-1 helped, but not totally. I ended up having to re-shoot a commercial job once because we just could not get rid of it, and it was a fairly neutral area like this one is.

 

Bring on the M9.....

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The M9 may or may not not make any difference depending on it's pixel count and sensor size. Aliasing artifacts like moire are a result of the combination of bayer interpolation, and the lens out resolving the sensor, which is why you only see it in the plane of focus.

 

Anti-aliasing filters effectively reduce the resolution of the lens to eliminate this problem. Leica's design choice ( which I approve of ) was to get maximum resolution most of the time, and deal with artifacts in software. This mostly works, but occasionally as you found out, software just is not enough.

 

If software solutions were perfect, than no-one would use AA filters.

 

Most digicams don't use them because their tiny sensors have 2-3 micron pixel pitch, and their lenses simply cannot resolve inside that.

 

If the M9 is FF and uses the same pixel size as the M8, ( hence the speculation at 18 mp), there will be no difference in resistance to artifacts except possibly in the corners where reduced resolution and contrast may have an impact.

 

One of the benefits of greater pixel density ( more sensor resolution ) is that the threshold for interpolation artifacts is reduced, or a less aggressive AA filter can be used (by those who use them), increasing sharpness.

 

I realize that this is a simplification of a very complex subject, but I hope it is useful.

 

Regards to alll ... Harold

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This is not just Moire. I've seen similar artifacts as part of the demosaic algorithms with raw converters. The looping shapes at the pixel resolution are reminiscent of some problems both ACR and Aperture had with files in the (distant) past.

 

What converter did you use for this?

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This is not just Moire. I've seen similar artifacts as part of the demosaic algorithms with raw converters. The looping shapes at the pixel resolution are reminiscent of some problems both ACR and Aperture had with files in the (distant) past.

 

Graham is right; while there may well be moire in there, at least part of what you're seeing is a maze pattern from the raw converter. The maze pattern may be being triggered by moire in the original image, but you may well get significantly better results from a different raw converter.

 

Sandy

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Right - the maze-like patterns are luminance interpretation faults subsequent to a moire pattern, the color rainbows are a chrominance moire effect.

 

The Nikon D70, which had improved sharpness over the D100 (less intense AA filter), also showed the maze effects (in jpegs - so it is an overall de-Bayerizing fault, caused or avoided by whatever software converts the image to a full rgb image - in-camera or in post-processing)

 

Nikon D70 Review: 17. Photographic tests: Digital Photography Review

 

Usually, I only get mazes in strong reds, like car taillights or traffic stop signals, where there is also an underlying fresnel lens pattern molded into the red plastic of the lights - usually.

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