From: Katharine Thayer (kthayer@pacifier.com)
Date: 09/13/03-08:25:37 AM Z
Greg Schmitz wrote:
>
> Sorry, but I can't keep my fingers off the keys. There is no
> difference between "density" and opacity. Go back and have a look at
> your textbooks. I think somebody already pointed out the relationship
> of opacity to density. Varying degrees of "opacity" are equivalent to
> varying degrees of density they are just expressed (mathematically) in
> a different fashion, but only if you're dealing with densitometry. Do
> you really thing about "density" when you photograph a tree?
>
> I think the confusion may stem from confusing methods used to read
> reflected density (reflected light actually) and transmitted density?
> It is possible that no light is making its' way to the paper, but
> rather that light which strikes the pigment is being reflected back
> from the pigment (hint - stop thinking in terms of gelatin/silver
> processes). Correct me if I'm wrong, but I think what Katherine means
> when she uses the term opaque is that no light is being reflected from
> the paper base, but rather the light is being reflected back from the
> surface of the pigment. A warning to those folks versed in
> Sensitometry - color densitometry is much different than B&W and
> colorimetry even mores so (IMHO :*).
>
I didn't see this post until Judy's reply made me go back and look for
it. I think the crucial point here is that the relationship people keep
insisting on between opacity and density works only for silver gel and
densitometry; in other words the people who were trying to read my
discussion in terms of those disciplines are missing my point, and they
are the ones who should stop thinking in terms of silver gel and
densitometry. I'm thinking only in terms of gum printing. The thing is
that you can't get around the fact that photographers who become gum
printers still use the word "density" to mean darkness of tone in a
print, and it's a useful word for the purpose, as long as other people
don't get all hung up on the silver-gel, densitometry meaning of the
term and say gum printers can't use it because it doesn't apply in
exactly the same way.
I think I've explained fully about the difference between transparent
and opaque paint and how that's a separate issue from dark and light in
gum printing. It's not about "confusing methods used to read reflected
density and transmitted density" whatever the heck that means. I'm not
talking about any of that, I'm just talking about understanding how
paint works. Transparent paint transmits light; opaque paint blocks
light. Transparent paint can be very light or very dark but transparent
throughout the range; opaque paint can be very light or very dark but
opaque throughout the range. I'm not sure which donkey the ears are
being pinned on; if it's me-- hee haw.
kt
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