This film density CURVE thang!

jjs wrote:
snip
What's that mean in terms I can plot/draw on the image?


The following paragraph applies to an average scene:

For printing on grade 3 paper (or VC equivalent) without any dodging or
burning, the blue box would be 2.2 lux-seconds wide and 0.88 negative
density units high. Left-right position of the box is determined by film
exposure, the up-down position is determined by printing exposure. The
print results then depend on where the blue box and film curve overlap.

For scenes with more or less subject brightness range, the blue box gets
wider/narrower. For more or less printing contrast, the box gets
shorter/higher (shorter box = more paper contrast needed for same print
results).

Your graph and box make an excellent illustration of the these
principles. And your observation about the 'S' shape and useful part of
the curve are quite accurate.

Research by Jones showed a subjective preference for B&W prints that
have a slight 'S' shape to the print density vs. subject brightness
curve. In practice, though, this is achieved with the combined effects
of film curve toe and paper curve toe/shoulder, not the film curve
alone. Whatever 'S' shape there is to a given film curve, it's difficult
to get both ends into that blue box. If you could, additional measures
would be needed to overcome the contribution from the paper curve shape.

D Poinsett

"Michael Scarpitti" wrote in message
om...
"jjs" wrote in message
...

See the following and let's work from there.
http://course1.winona.edu/jstafford/...5mm_curves.gif

I added the blue box. DOES this blue box represent the USEFUL part of
the
curve? If it does, then Scarpitti would seem to be quite deluded. If it
does
not, then please correct me.

It depends on the secene and the degree of development. What made you
choose the limits you did?

I chose it rather arbitrarily, hoping that someone could provide a
definitive answer. I'm wondering exactly what density range is most useful
in the negative - perhpaps the weakest shadow to the first unblocked
highlight on #3 or #2 paper.

"Michael Scarpitti" wrote in message
om...
"jjs" wrote in message
...

See the following and let's work from there.
http://course1.winona.edu/jstafford/...5mm_curves.gif

I added the blue box. DOES this blue box represent the USEFUL part of
the
curve? If it does, then Scarpitti would seem to be quite deluded. If it
does
not, then please correct me.

It depends on the secene and the degree of development. What made you
choose the limits you did?

I chose it rather arbitrarily, hoping that someone could provide a
definitive answer. I'm wondering exactly what density range is most useful
in the negative - perhpaps the weakest shadow to the first unblocked
highlight on #3 or #2 paper.

"Michael Scarpitti" wrote in message
om...

How so? Even if all of the curve is not used except in extreme
circumstances, the SHAPE of the curve still affects tone reproduction.

Indeed, there is a profound virtue in the shape of a curve. If my ignorant
blue-box guess is correct, there isn't much of a 'shape' per-se, but just a
slope.

"Michael Scarpitti" wrote in message
om...

How so? Even if all of the curve is not used except in extreme
circumstances, the SHAPE of the curve still affects tone reproduction.

Indeed, there is a profound virtue in the shape of a curve. If my ignorant
blue-box guess is correct, there isn't much of a 'shape' per-se, but just a
slope.

jjs wrote:
: Okay, now Michael Scarpitti asserts that Tri-X has an 'S' type curve, or
: something similar.

: Now help me out. When you look at Kodak's published density curve, just HOW
: MUCH of that plotted curve is useful to a 35mm photographer? Does the chart
: cover far more than the actual useful density range for printing?

: See the following and let's work from there.
: http://course1.winona.edu/jstafford/...5mm_curves.gif

: I added the blue box. DOES this blue box represent the USEFUL part of the
: curve? If it does, then Scarpitti would seem to be quite deluded. If it does
: not, then please correct me.

Before giving my opinion I want to qualify my answer a bit. First my density testing is
limited to film testing. With the rare exception of idle curiositySP? I don't take
density readings of actual negatives. The second is that as most of you should know by
now I use the zone system for determining both the exposure and development time.

The film speed testing I do puts zone I at .1 over FB+F which is right at the toe of
the film. I have tuned my development times to fit my "important" highlights within the
range of my paper. In my case the enlarger and paper combination I normally use gives
me highlight density at ~1.53 above FB+F. I suppose this means that I stay within the
lower part of the curve.

For me this has been consistent irregardless of what film/developer I've used. A short
list of the films that come quickly to mind include Ilfords' hp and fp films as well
Tri-x, Bergger and most recently the Tmax and Delta films. It's also not uncommon to
see detail in the density extremes of a negative that is simply not printable.

I know it's not as "scientific as you may want but I do know that when I look at the
exposure curve of film I'm interested in the lower part of the curve. I'm actually more
interested in the contrast-index curve(Kodak's term) since that shows me the effect of
the development time on the contrast of the film.

--




Keep working millions on welfare depend on you
-------------------

jjs wrote:
: Okay, now Michael Scarpitti asserts that Tri-X has an 'S' type curve, or
: something similar.

: Now help me out. When you look at Kodak's published density curve, just HOW
: MUCH of that plotted curve is useful to a 35mm photographer? Does the chart
: cover far more than the actual useful density range for printing?

: See the following and let's work from there.
: http://course1.winona.edu/jstafford/...5mm_curves.gif

: I added the blue box. DOES this blue box represent the USEFUL part of the
: curve? If it does, then Scarpitti would seem to be quite deluded. If it does
: not, then please correct me.

Before giving my opinion I want to qualify my answer a bit. First my density testing is
limited to film testing. With the rare exception of idle curiositySP? I don't take
density readings of actual negatives. The second is that as most of you should know by
now I use the zone system for determining both the exposure and development time.

The film speed testing I do puts zone I at .1 over FB+F which is right at the toe of
the film. I have tuned my development times to fit my "important" highlights within the
range of my paper. In my case the enlarger and paper combination I normally use gives
me highlight density at ~1.53 above FB+F. I suppose this means that I stay within the
lower part of the curve.

For me this has been consistent irregardless of what film/developer I've used. A short
list of the films that come quickly to mind include Ilfords' hp and fp films as well
Tri-x, Bergger and most recently the Tmax and Delta films. It's also not uncommon to
see detail in the density extremes of a negative that is simply not printable.

I know it's not as "scientific as you may want but I do know that when I look at the
exposure curve of film I'm interested in the lower part of the curve. I'm actually more
interested in the contrast-index curve(Kodak's term) since that shows me the effect of
the development time on the contrast of the film.

--




Keep working millions on welfare depend on you
-------------------

On 7/31/2004 7:57 AM Michael Scarpitti spake thus:

David Nebenzahl wrote in message
...

On 7/30/2004 8:16 PM Michael Scarpitti spake thus:

"jjs" wrote in message
...

Okay, now Michael Scarpitti asserts that Tri-X has an 'S' type curve, or
something similar.

Now help me out. When you look at Kodak's published density curve, just
HOW MUCH of that plotted curve is useful to a 35mm photographer? Does the
chart cover far more than the actual useful density range for printing?

See the following and let's work from there.
http://course1.winona.edu/jstafford/...5mm_curves.gif

I added the blue box. DOES this blue box represent the USEFUL part of the
curve? If it does, then Scarpitti would seem to be quite deluded.

How so? Even if all of the curve is not used except in extreme
circumstances, the SHAPE of the curve still affects tone reproduction.

Wrong-o: only that part of the curve which is actually being "used" (i.e.,
that part which covers the light values *in the scene being photographed*)
affects tone reproduction *for that exposure*.

Even you should know *that*.

Yes, of course, I meant the shape of the curve being used....that goes
without saying.

Well, then, using J. Stafford's above-given example (if it is correct), the
parts of the film's curves that he's using (what's inside his blue box) are
pretty much straight lines, with no appreciable S-curve shape at all. So how
does that square with your assertion?


--
Everybody's worried about stopping terrorism. Well, there's a
really easy way: stop participating in it.

- Noam Chomsky

On 7/31/2004 7:57 AM Michael Scarpitti spake thus:

David Nebenzahl wrote in message
...

On 7/30/2004 8:16 PM Michael Scarpitti spake thus:

"jjs" wrote in message
...

Okay, now Michael Scarpitti asserts that Tri-X has an 'S' type curve, or
something similar.

Now help me out. When you look at Kodak's published density curve, just
HOW MUCH of that plotted curve is useful to a 35mm photographer? Does the
chart cover far more than the actual useful density range for printing?

See the following and let's work from there.
http://course1.winona.edu/jstafford/...5mm_curves.gif

I added the blue box. DOES this blue box represent the USEFUL part of the
curve? If it does, then Scarpitti would seem to be quite deluded.

How so? Even if all of the curve is not used except in extreme
circumstances, the SHAPE of the curve still affects tone reproduction.

Wrong-o: only that part of the curve which is actually being "used" (i.e.,
that part which covers the light values *in the scene being photographed*)
affects tone reproduction *for that exposure*.

Even you should know *that*.

Yes, of course, I meant the shape of the curve being used....that goes
without saying.

Well, then, using J. Stafford's above-given example (if it is correct), the
parts of the film's curves that he's using (what's inside his blue box) are
pretty much straight lines, with no appreciable S-curve shape at all. So how
does that square with your assertion?


--
Everybody's worried about stopping terrorism. Well, there's a
really easy way: stop participating in it.

- Noam Chomsky

On 7/31/2004 9:20 AM Frank Pittel spake thus:

jjs wrote:

Okay, now Michael Scarpitti asserts that Tri-X has an 'S' type curve, or
something similar.

Now help me out. When you look at Kodak's published density curve, just
HOW MUCH of that plotted curve is useful to a 35mm photographer? Does the
chart cover far more than the actual useful density range for printing?

See the following and let's work from there.
http://course1.winona.edu/jstafford/...5mm_curves.gif

I added the blue box. DOES this blue box represent the USEFUL part of the
curve? If it does, then Scarpitti would seem to be quite deluded. If it
does not, then please correct me.

Before giving my opinion I want to qualify my answer a bit. First my
density testing is limited to film testing. With the rare exception of idle
curiositySP?

Relax, Frank: lately, all of those SP?s you've put in have been after
correctly-spelled words. You're getting a little gun-shy.

Consider this a spelling flame in reverse.


--
Everybody's worried about stopping terrorism. Well, there's a
really easy way: stop participating in it.

- Noam Chomsky