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My medium format digital journey - Moiré & aliasing

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Article Index
My medium format digital journey
raw images for download
Where do I stand now
The experience
Color Profiles
Resolution Tests
Real World Samples
Color rendition
Dynamic Range
Moiré & aliasing
DoF and diffraction
More real world images
Three format comparison
Diffractio series
The lenses
The Bad News
Capture One or LR 4.4
Some comments on Phase One business model
The Ultimate Platform?
All Pages

Moiré and aliasing artifacts

The P45+ does not have an OLP (Optical Low Pass) filter like DSLRs normally have. The sensor has relatively large pixels, 6.8 micron pitch. The combination of large pixels, good lenses and no OLP filtering is expected to produce aliasing artifacts and color Moiré. Regarding aliasing it may be not to bad, but I have seen some color moiré on most of my test pictures. It seems that Capture 1 yields less moiré than Lightroom 4.4 and both have quite efficient tools to reduce color moiré.

Here the image on top is converted by LR4 and the bottom with C1.

The feather image

The image below was shot with the P45, Sonnar 150/4 about 3.5m distance. The image contains a lot of aliasing artifacts, except color moiré it has a lot of discontinous strain and downward bent strains on the right side. Note also a hatch pattern at the bottom. I compared the P45+ image with two images shot with my Sony, also with 150 mm and at the same distance and same light. The Sonys produce a much cleaner image, due to higher resolution (because denser pixel pitch) and OLP filtering. 

Comparison below shows P45+ to the left and the Alpha 77 to the right, would the Alpha 77 have the same sensor size as the P45+ it would have 114 MP.
P45+Alpha 77 SLT
P45 to the left, Alpha 77 to the right.

The image above essentially says that high sensor resolution with OLP-filtering is much preferable to lower resolution without OLP-filtering. Moiré reduction in LR4 or Capture 1 removes the color moiré, by local desaturation of color, but does little to the other artifacts.

Last Updated on Thursday, 08 August 2013 12:38  


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