Graded paper

How are the grades of graded paper made different in contrast?

Grain size?

UC wrote:

How are the grades of graded paper made different in contrast?

Grain size?

The simplest way would be through variation of the distribution of grain
sizes. If you have a broad distribution, large grains would be exposed
at lower light intensities than small grains, extending the response (low
contrast; long exposure scale). With a very narrow size distribution,
you move toward an all-or-none effect, where a small increase in exposure will
completely expose the smallest grains (high contrast grades; short exposure scale).

Additionally, the grains are chemically sensitized, and I'd imagine
that there are patents related to that, blending, etc. as well as trade
secrets.

If you want to change the contrast of high contrast paper or lith film,
or extend the scale of pictorial film, the film or paper may be treated
with a very dilute proportional reducer (ferricyanide) prior to development.
That treatment lowers the "contrast" of the latent image (actually it reverses
some of the exposure by removing latent silver centers). That approach is
outlined in my reply at:

http://www.largeformatphotography.in...ic/505080.html

Richard may have more detailed information - I think he has a reference books on
emulsion making. I haven't looked at that literature for a long time (decades).

Michael Gudzinowicz wrote:
UC wrote:

How are the grades of graded paper made different in contrast?

Grain size?

The simplest way would be through variation of the distribution of grain
sizes.

That's what I thought, but image color varies with grain size. There
must be something more to it.

If you have a broad distribution, large grains would be exposed
at lower light intensities than small grains, extending the response (low
contrast; long exposure scale). With a very narrow size distribution,
you move toward an all-or-none effect, where a small increase in exposure will
completely expose the smallest grains (high contrast grades; short exposure scale).

Additionally, the grains are chemically sensitized, and I'd imagine
that there are patents related to that, blending, etc. as well as trade
secrets.

If you want to change the contrast of high contrast paper or lith film,
or extend the scale of pictorial film, the film or paper may be treated
with a very dilute proportional reducer (ferricyanide) prior to development.
That treatment lowers the "contrast" of the latent image (actually it reverses
some of the exposure by removing latent silver centers). That approach is
outlined in my reply at:

http://www.largeformatphotography.in...ic/505080.html

Richard may have more detailed information - I think he has a reference books on
emulsion making. I haven't looked at that literature for a long time (decades).

UC wrote:

Michael Gudzinowicz wrote:

UC wrote:


How are the grades of graded paper made different in contrast?

Grain size?

The simplest way would be through variation of the distribution of grain
sizes.


That's what I thought, but image color varies with grain size. There
must be something more to it.


Image color is due to Mie scattering in the developed emulsion, which is
related to grain size. However, scattering or color per se doesn't determine
spectral sensitization or contrast of the emulsion.

Mie scattering and image color was reviewed in the Nov. 1991 issue of
"Scientific American" by Lam and Rossiter in their article on chromoskedasic
printing. Dr. William Jolly improved and extended the methodology in three
articles appearing in Darkroom & Creative Camera Techniques:

Chromoskedasic Duotone Pseudosolarization
By William L. Jolly (D&CCT, 13, issue 6, page 30 (1992))

Dramatic Duotone Solarization
By William L. Jolly (D&CCT, 14, issue 4, page 19.(1993))

Chromoskedasic Pseudosolarization Update
By William L. Jolly (D&CCT, 14, issue 5, page 28 (1993))

If you're interested in image color, they are worth reading if
you haven't done so. At one time the articles were posted to the web
from Dr. Jolly's U.Ca. Berkeley web site. I don't know if they
still are available.


If you have a broad distribution, large grains would be exposed
at lower light intensities than small grains, extending the response (low
contrast; long exposure scale). With a very narrow size distribution,
you move toward an all-or-none effect, where a small increase in exposure will
completely expose the smallest grains (high contrast grades; short exposure scale).

Additionally, the grains are chemically sensitized, and I'd imagine
that there are patents related to that, blending, etc. as well as trade
secrets.

If you want to change the contrast of high contrast paper or lith film,
or extend the scale of pictorial film, the film or paper may be treated
with a very dilute proportional reducer (ferricyanide) prior to development.
That treatment lowers the "contrast" of the latent image (actually it reverses
some of the exposure by removing latent silver centers). That approach is
outlined in my reply at:

http://www.largeformatphotography.in...ic/505080.html

Richard may have more detailed information - I think he has a reference books on
emulsion making. I haven't looked at that literature for a long time (decades).

Higher-grade papers have always been slower, which supports the idea
that they are finer-grained. But I keep thinking there is more to it
than that.

Michael Gudzinowicz wrote:
UC wrote:

Michael Gudzinowicz wrote:

UC wrote:


How are the grades of graded paper made different in contrast?

Grain size?

The simplest way would be through variation of the distribution of grain
sizes.


That's what I thought, but image color varies with grain size. There
must be something more to it.


Image color is due to Mie scattering in the developed emulsion, which is
related to grain size. However, scattering or color per se doesn't determine
spectral sensitization or contrast of the emulsion.

Mie scattering and image color was reviewed in the Nov. 1991 issue of
"Scientific American" by Lam and Rossiter in their article on chromoskedasic
printing. Dr. William Jolly improved and extended the methodology in three
articles appearing in Darkroom & Creative Camera Techniques:

Chromoskedasic Duotone Pseudosolarization
By William L. Jolly (D&CCT, 13, issue 6, page 30 (1992))

Dramatic Duotone Solarization
By William L. Jolly (D&CCT, 14, issue 4, page 19.(1993))

Chromoskedasic Pseudosolarization Update
By William L. Jolly (D&CCT, 14, issue 5, page 28 (1993))

If you're interested in image color, they are worth reading if
you haven't done so. At one time the articles were posted to the web
from Dr. Jolly's U.Ca. Berkeley web site. I don't know if they
still are available.


If you have a broad distribution, large grains would be exposed
at lower light intensities than small grains, extending the response (low
contrast; long exposure scale). With a very narrow size distribution,
you move toward an all-or-none effect, where a small increase in exposure will
completely expose the smallest grains (high contrast grades; short exposure scale).

Additionally, the grains are chemically sensitized, and I'd imagine
that there are patents related to that, blending, etc. as well as trade
secrets.

If you want to change the contrast of high contrast paper or lith film,
or extend the scale of pictorial film, the film or paper may be treated
with a very dilute proportional reducer (ferricyanide) prior to development.
That treatment lowers the "contrast" of the latent image (actually it reverses
some of the exposure by removing latent silver centers). That approach is
outlined in my reply at:

http://www.largeformatphotography.in...ic/505080.html

Richard may have more detailed information - I think he has a reference books on
emulsion making. I haven't looked at that literature for a long time (decades).

UC wrote:

Higher-grade papers have always been slower, which supports the idea
that they are finer-grained. But I keep thinking there is more to it
than that.

That's not what I said or intended to imply. It's the Gaussian spread or
distribution of sizes that determines contrast or exposure scale for
unsensitized emulsions.

A narrow size range (large or small grains) requires less of a difference in
exposure to expose all grains since speeds are similar. The grain size per se to
some degree will affect color. Very fine grain emulsions are warmer than large
coarse grains. However, either can be high or low contrast depending on the
spread of sizes. The fine grain emulsions (and coarse) are sensitized to blue
and green (the later resulted in "Rapid" graded papers), or else they would only
respond to UV light like salt prints. Speed can vary with grade, or a
manufacturer can use different degrees of chemical sensitization to match
midtone ANSI printing speeds of different grades (which usually is/was the case).

The reason the paper emulsions use a very fine grain compared to film, is
to improve image density without wasting silver. Very fine grains when developed
have better covering power. An analogy would be covering a light box with a
millimeter of graphite powder blocking all light, vs. a single "silver rich"
layer of black golf balls, that transmits light.

The other reason is that the size distribution is easier to control.

You are correct... it is more complicated and that is reflected in the
dedication of books to the subject.

OK, so narrow size range, again what I was thinking. But if that's all
there is to it, how do they keep the same 'look' to the papers?
High-contrast papers are slower, usually, which is not a bad thing when
you realize that thin negatives are likely to be the ones printed
onhigh-contrast paper.


Michael Gudzinowicz wrote:
UC wrote:

Higher-grade papers have always been slower, which supports the idea
that they are finer-grained. But I keep thinking there is more to it
than that.

That's not what I said or intended to imply. It's the Gaussian spread or
distribution of sizes that determines contrast or exposure scale for
unsensitized emulsions.

I understand that. Perhaps I was not clear.

A narrow size range (large or small grains) requires less of a difference in
exposure to expose all grains since speeds are similar. The grain size per se to
some degree will affect color. Very fine grain emulsions are warmer than large
coarse grains.

Yes, this I know.

However, either can be high or low contrast depending on the
spread of sizes.

OK, this is something I am familiar with.

The fine grain emulsions (and coarse) are sensitized to blue
and green (the later resulted in "Rapid" graded papers), or else they would only
respond to UV light like salt prints. Speed can vary with grade, or a
manufacturer can use different degrees of chemical sensitization to match
midtone ANSI printing speeds of different grades (which usually is/was the case).


How about bromide/chloride ratios?

The reason the paper emulsions use a very fine grain compared to film, is
to improve image density without wasting silver.

And because you don't need film-like speed.

Very fine grains when developed
have better covering power. An analogy would be covering a light box with a
millimeter of graphite powder blocking all light, vs. a single "silver rich"
layer of black golf balls, that transmits light.

Oh, so true. The ads for 'silver-rich' films and papers crack me up.


The other reason is that the size distribution is easier to control.

Good to know that.


You are correct... it is more complicated and that is reflected in the
dedication of books to the subject.

"Michael Gudzinowicz" wrote

Mie scattering and image color was reviewed in the Nov. 1991 issue of
"Scientific American" by Lam and Rossiter in their article on chromoskedasic
printing. Dr. William Jolly improved and extended the methodology in three
articles appearing in Darkroom & Creative Camera Techniques [I don't know
if they are still available]

A chromoskedasic photographic print:

http://www.cchem.berkeley.edu/wljeme/fig6.2.jpg

Googling for

jolly chromoskedasic

[I have heard of "The Jolly Tinker", but this is takes it to a new level]

brings up:

http://www.cchem.berkeley.edu/wljeme/Chapt6.html

lam rossiter chromoskedasic

http://www.chemigramist.com/chromoskedasic.html

etc. etc. etc...

Enough to bring on chromosdislexia.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
Fstop timer - http://www.nolindan.com/da/fstop/index.htm

Nicholas O. Lindan wrote:

Well, you found the trove that I felt had disappeared years ago.

The link to Jolly's entire online book on solarization theory and
methodology is: http://www.cchem.berkeley.edu/wljeme/

The "chemigram" site's galleries and informational links are worth
a click to browse through: http://www.chemigramist.com/

The links go to some of Teske's prints, Yurow's page on solution
physical development, and other useful topics. Searching on the
names of some of the artists with a term like "photogram" will
brings up more applications and prints.

Thanks,

Mike



"Michael Gudzinowicz" wrote


Mie scattering and image color was reviewed in the Nov. 1991 issue of
"Scientific American" by Lam and Rossiter in their article on chromoskedasic
printing. Dr. William Jolly improved and extended the methodology in three
articles appearing in Darkroom & Creative Camera Techniques [I don't know
if they are still available]


A chromoskedasic photographic print:

http://www.cchem.berkeley.edu/wljeme/fig6.2.jpg

Googling for

jolly chromoskedasic

[I have heard of "The Jolly Tinker", but this is takes it to a new level]

brings up:

http://www.cchem.berkeley.edu/wljeme/Chapt6.html

lam rossiter chromoskedasic

http://www.chemigramist.com/chromoskedasic.html

etc. etc. etc...

Enough to bring on chromosdislexia.

Michael Gudzinowicz wrote:

The reason the paper emulsions use a very fine grain
compared to film, is to improve image density without
wasting silver. Very fine grains when developed
have better covering power.


Might that read; Very fine grains when finely developed have ...?
My understanding is that the processing ph affects grain size. The
lower the ph the finer the grain. So I'd think maximum density
in a print results from low ph processing.
I did an experiment with an RC paper developed in D-23 diluted
1:3. I was impressed by the black density. The print did need
more exposure than a similar carbonated Ansco 120. Dan