Today Roger N. Clark (change username to rnclark) spoke these
views with conviction for everyone's edification:

Enlarging and shrinking an image requires interpolation.
ALL interpolation algorithms have artifacts, at least all
I've seen. If you compare your original small image with
the largest one, you can see artifacts. I'll point out
one.

Resampling using any algorithm, interpolation or simple pixel
resize, can and does produce damage. But the term "artifact"
first came to prominence during the early experiences with
JPEG, after people first saw the damage from over compression.

From the left, go to the first raised rifle and the guy
standing
below the raised rifle (looks like his tongue is sticking
out). No go to the next guy to the right in front. He has
a funny smile with his mouth curved upward in an unnatural
way (his left side) and a line goes almost up to his nose.
If you look at the original image, it is obvious that area
is really a shadow from his cheek. The interpolation
mangled the guy's smile. I suspect the noise that was
added in as to mask artifacts, but in my opinion, was done
very well. Other artifacts include halos around contrast
boundaries, a common sharpening artifact.

I already said I could see the artefacts, but I don't think
they were caused by resizing down to the original size I have
from whatever it was originally scanned at, nor when it was
resized up. Exagerated, yes. Created, I don't think so.

Being that I'm a visual sort of a guy, I don't know how to use
the analytical tools in PSP 9 to examine an image, and I don't
parlez vous PS CS. So, I'm very curious to know how you can
tell that your examples above were caused by interpolation and
not the more likely cause, over compression at some point,
and/or multiple open/edit/re-save cycles.

--
ATM, aka Jerry