P: Artefacts when using shadows, clarity and image warp (lens corrections)

This is a limitation of the current technology, a tradeoff we had to make to keep performance reasonable (otherwise to use the Highlights, Shadows, or Clarity sliders would be several times slower and use a lot more memory ...)

LR 4.1 final and ACR 7.1 final: The "thick" artefacts when using lens corrections are gone, but the "thin" variant shown in my post above are still there. Note: The artefacts still change shape when changing lens correction parameters, but they always stay "thin".

I am slightly disappointed. However, the "thin" variant is probably visible only in 100% view on monitor. I am not sure whether it is visible in normal cases, e.g. prints.

As I already said:

I can see the same artifacts, but it only appears where there is chromatic aberration and/or fringing present in the image. It looks like Clarity is being applied to the image prior to CA and/or Defringe removal, because you can still see it with these two tools enabled. The high Clarity setting to seems to amplify the CA.

When LR builds the preview or export image it applies the Develop settings using several operations and several bitmaps, which are then merged to create the final processed output. What I think is happening is that the Clarity processing uses a bitmap that does NOT have any CA settings applied to it. This accentuates the CA (i.e. fringing), leaving halo like artifacts even after CA processing is applied.

LR3 'Fill' tool creates similar halo artifacts perhaps for the same reason, but we all assumed this was corrected in LR4.

Thanks Todd.

I did as you suggested and experimented a bit. There was very little difference with the high contrast edges between PV2010 and PV2012 with or without Lens Corrections using a baseline image. But like LRusser24 I obtained similar results (I'll call it the barber pole effect) when applying Clarity with or without Lens Corrections (distortion and CR) applied.

Attached are two screen captures (100% crop in LR) including the settings panel.

Left is PV2012 w/Lens Correction/Clarity 0.
Right is PV2012 w/Lens Correction/Clarity 50.
Clarity set at 50 exaggerates the artifacts, but I was seeing those effects at Clarity 10.

I think you are seeing the difference between PV2010 's Develop settings and PV2012 "automatic" White and Black point settings. PV2012 shows more detail in the shadows and highlights, which is not a defect. It's just accentuating the lens defects.

Try this:

Adjust the image file using only PV2010 Basic controls and everything else turned off (zero'd as you say). Now create a virtual copy, change the copy to PV2012, and adjust the Basic controls so it looks as close as possible to the PV2010 image. When done the two Histograms should look virtually identical

Do you still this "hard edge high contrast artifact" in the PV2012 image with no other adjustments (i.e. No Lens Corrections tools) applied?

Lightroom 4.1RC2 (Process version 2012)
As above, but there's more going on than just Lens Correction. Using just the Basic Panel for adjustments (everything else zeroed) there is still this hard edge high contrast artifact. Lens Correction certainly dramatically adds to the effect.

Adjust a photo using Process version 2010 then select Process version 2012
(Camera Calibration Panel.) Compare the high contrast edges in the same adjusted photo with Process version 2012 and Process version 2010.

Applying lens profile corrections is producing very strange artifacts on some hard contrasty edges

I can see the same artifacts, but it only appears where there is chromatic aberration and/or fringing present in the image. It looks like Clarity is being applied to the image prior to CA and/or Defringe removal, because you can still see it with these two tools enabled. The high Clarity setting to seems to amplify the CA.

I sure hope the fix for the original problem will remove or at least reduce this artifact.

Could be... but the artefacts in the second image look "funny". They art not halos or the like, but "jagged" structures with alternating dark and light lines in one-pixel intervals. That is not the artefact I would expect from a clarity limitation.

Might be a limitation of Clarity.