It's a puzzling effect, but it does not produce artifact-free results, on the contrary.
To be continued, when I better understand what happens, and what to do about it.
I've made an animation of the cropped center of a single Raw file of my
resolution target. The center crop has been zoomed in to 400% to make it easier to see what happens, so at 100% zoom or smaller the artifacts are less visible, but they do make postprocessing (e.g. sharpening) more error prone.
Some of the False color artifacts can be mitigated a bit by some of the conversters, but I used non-adjusted Raw conversions, with all sharpening and noise reduction disabled.
My personal favorite still is Capture One, which produces images with very high resolution with a minimum of artifacts that can cause issues in subsequent processing. I've shown a Version 8 conversion, but version 9 produces identical results. RawTherapee (not shown here) produces results that are
very close to Capture One's.
Lightroom (version 5.7 produces indentical results to the current versions) is a bit behind in both resolution and false color artifacting. As said, the false color artifacts can be mitigated a bit, but there are other converters that have more effective tools for that. On occasion Lightroom will produce edge artifacts that are more prominent than those shown here.
OnOne Photo RAW is very aggressive in extracting detail, and that results in mazing artifacts that even limit resolution before it reaches the file limits. The artifacts and lower resolution produce a gritty look the closer one gets to the file's limiting resolution. In addition, the default conversion (without sharpening or noise reduction) already seems to apply significant sharpening that cannot be disabled or controlled, and that leads to halos on sharp edges. The shown region of the resolution target only has smooth sinusoidal features, so the halos are not that obvious although it tends to exaggerate the contrast of small detail.
As a bonus, I've added a crop from the Affinity Photo Beta version 1.5.0.39 for Windows. I'm not sure if the Mac version produces the same results. The Windows version is clearly a Beta version with some issues that need to be ironed out, but they are working hard to solve them before official release. The recent update, to my eyes, also improved/changed the Raw conversion quality a bit, so I'll reserve a final judgement for the final version. However, the current version is quite aggressive in extracting maximum detail, which results in some false color artifacting, and some mazing artifacts at the very limit of resolution. One could paint in some (Chroma) noise reduction to mitigate the most visible issues.
The image I used was shot on a Canon 1Ds Mark III, with the EF-135mm f/2.0 L lens at its optimal resolution aperture, on a heavy tripod. I made sure to get the best possible focus with that combination by bracketing the focus position with a focus rail, and picking the measured highest resolution frame. Raw conversions were all done without sharpening or noise reduction.
That also means that cameras without an anti-aliasing filter will cause even more prominent artifacts, and that also explains why Capture One does so well (given its legacy with having to deal with MF sensor images with large sensor elements without low-pass filter or microlenses).
The artifacts will probably not be as prominent with lower quality lenses or with slight defocus (even as it approaches the boundaries of the DOF zone). A bit of defocus blur, camera shake, diffraction, subject motion, will reduce resolution and thus make for a less critial Demosaicing and Raw conversion.
So my test will bring out the issues one can expect if everything else is optimal. With lesser technique the issues will be less obvious, but then the whole image will be of lower technical quality.
Cheers,
Bart
P.S. The green circle represents the Nyquist limit, so anything inside that circle is aliasing which one can only hope is not too obtrusive. As detail approach and exceed the Nyquist limit, the micro-contrast would ideally fade to uniform gray if we want to avoid all aliasing artifacts.