Christian Walther <cwa### [at] gmxch> wrote:
> Kenneth wrote:

>
> I just followed some links from there and ended up at an interesting
> article that seems to contradict what I said about the moon:
> <http://www.optics.arizona.edu/Palmer/moon/lunacy.htm> (Caution: his GIF
> images of a lambertian sphere are encoded with a gamma of 1 and don't
> appear correctly on usual displays! In fact, I wouldn't be too surprised
> if they were made using POV-Ray without an assumed_gamma statement.)

That's a really fascinating, in-depth look at what is happening to light as
it reflects off the moon. Lots of "ingredients" go into it, apparently.
Thanks for posting the url; it's a question that has puzzled me long before
I picked up POV.

My own take on his CGI-rendered lambertian image is that it's pretty
spot-on! (But then, you probably expected that, eh? ;-)  )  But if that
image was created incorrectly (or displays incorrectly), wouldn't his
entire argument fall flat? He's using it as the core of his discussion, so
I expect that he went to some pains to reproduce true lambertian
characteristics. Yes, it would be interesting to know what program he
created that image on. Thought of e-mailing him; may still do so.
>
> > Before commenting further, a quick question: What computer
> > system are you running POV on?
>
> Mac OS X on PPC G4, mostly. Occasionally, Linux or Windows on x86. Why?

Well, I had begun to think that different versions of POV (on different
platforms) might be producing images differently, gamma-wise--leading to
wildly opposite viewpoints such as we have.  Although there may be
something to that (don't really know, but I'm guessing not), I've put aside
that line of thought for the time being.

But while we're on the subject--would you mind telling me what overall gamma
your various monitor/OS systems are set to? If they're "largely" different
from mine, that might explain part of our disagreement.

But I've been doing my homework--lots of gamma research--and there's just
something *wrong* with this entire POV picture. Not absolutely SURE yet what
that something is, but I'm methodically tracking it down.  Stay tuned!

Ken Walker,
bloodhound

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