I didn't notice any artifacts, either, but FWIW, in Jeffrey Friedl's An Analysis of Lightroom JPEG Export Quality Settings, he makes a comment that “Firefox does not handle display of JPEGs very well, sometimes introducing horrible posterization that does not actually exist in the image.”
See also a few of the comments beneath that post (search for “Firefox”), but there's no real conclusion about it.
That's actually the article which prompted me to change to lower export settings Didn't notice the blurb about the posterization, there are several comments about the issue, and further googling confirms
I'm not the only one who ran into this. Whew...
I played around again with
Gary Ballard's exhaustive browser color management page, which confirms FF and Safari are color managed. Opera is not color managed, same with IE. Perhaps FF's and Safari's schizophrenic approach to color management is the reason for the artifacts?
and another edit:
found the culprit!
Gary Ballard's page linked above put me on the right track: newest FF has color management on by default. The entry
gfx.color_management.mode in
about:config is at 2 (
enable color management for tagged graphics only) by default. Setting it at 1 (enable color management for rendered graphics) still has artifacts, but at 0 (disable color management) they are gone!
Given that FF and Safari are color managed and show artifacts, while Safari and Opera are not color managed and artifacts are absent, the blame is on color management, or its implementation at some point in the input-output chain. Perhaps this is just a result of a (yet another) half-assed implementation of color management in the browsers.
Does LR3 embed the ICC profile in JPEGs on export?
I'm on Windows 7 with Fire Fox (NEC P221) and they all look fine to me, though as a previous poster noted it may not be possible to see flaws at this resolution.
As I pointed out they are clearly visible at the res posted.