Bases on some comments about this, I did some checking.
I reconverted the E-M5, ISO 3200 file. I discovered that PS had somehow
got sharpening on again, but NR off. Maybe when I installed CC? So I
tried again, sans sharpening.
AG's comments about different processors got me to run it through
Viewer3, too.
So, the worms I showed are artifacts of PS's input sharpening. You'd
think that's a problem solved.
BUT - the V3 output, sharpening off, is better. Color noise is far
better handled than I've managed with NI. Where there are little hints
and swirls of blue and yellow in the purple from NI (Pixel level
obsessiveness), V3 gives even, correct seeming color.
I go back into V3, and find the NR IS already off, although the output
clearly has had quite effective NR applied. WTF? I've hardly used it, so
perhaps there's some other way to control NR - other than the switch
that say it does? Was sharpening really off, even though it says so, too?
This is most disturbing. I wouldn't so much mind converting using V3,
but I already know it's hopeless with recovering highlights. I really
don't want to have a dual work flow, V3 for higher ISO, ACR for
highlights, then merge! ICK!
This really brings home how different various sensor systems can be. The
E-M5 and GX7 seem to have such similar systems, but the same settings in
ACR result in worms from one and not from the other.
More futzing to do, I suppose. :-(
Confuse A. Moose