Reciprocity

In the past reciprocity has been a concern when processing films if the
chemicals and water vary too much in temperature. Is this still true
with modern b/w film emulsions?

I am not sure what you mean by reciprocity. In photography this term
usually refers to reciprocity law failure, that is, that while the
total light energy should result in the same exposure in practice the
time of exposure or intensity does make a difference. Very long and
very short exposures do not have the same effect as a medium speed
exposure. This effect is a characteristic of the emulsion and is not
affected by the developer or temperature.
Now, if you are refering to the rate at which development varies
with temperature, there is certainly variation. It is partly due to the
developer and partly the film. For one thing some developing agents
change activity faster with temperature than others. Also, the pH of
the developer has an effect on the above. At low temperatures for
instance, Hydroquinone tends to become inactive. This effect depends
on pH. The effect is most apparent in normal film and print developers
of medium pH. In very high pH developer such as high contrast or lith
developer, Hydroquinone stays active at low temperatures.
Kodak and other developer manufacturers, have charts showing the
rate at which developers change activity.
I hope one of these addresses your question.

--
Richard Knoppow

In article ,
(Blaine Owens) writes:

In the past reciprocity has been a concern when processing films if the
chemicals and water vary too much in temperature. Is this still true
with modern b/w film emulsions?

I suspect you're thinking of reticulation, not reciprocity. The latter
term is generally used in the phrase "reciprocity failure," which is a
situation in which unusually long or short exposure durations require an
adjustment to the exposure compared to what you'd expect based on meter
readings, since the film's response to light intensity isn't linear in
very intense or dim light. AFAIK, there's no connection between
reciprocity effects and developer temperature, aside from the fact that
you can adjust the degree of development by adjusting temperature, which
will interact with exposure errors due to reciprocity failure.

Reticulation is an effect of changing the film's temperature too quickly,
as when moving film from solutions of varying temperature. The result is a
web of cracks in the emulsion, which show up as lines in prints. Modern
films from the big B&W players in the US (Kodak, Ilford, and Fuji) are
pretty resistant to reticulation, although I wouldn't recommend using
solutions that alternate between near-frozen and near-boiling. I don't
know how Efke, Foma, Lucky, or other "exotic" (in the US) films fare in
this respect, although I've not had problems with Foma, and I've shot a
fair amount of it and not controlled temperatures too closely after the
developer. That said, most of my solutions are at room temperature, since
that's how they're stored. My rinse water varies more, since I pull that
directly out of the tap, and I adjust the temperature by feel.

--
Rod Smith,
http://www.rodsbooks.com
Author of books on Linux, FreeBSD, and networking

"Blaine Owens" wrote

In the past reciprocity has been a concern when processing films if the
chemicals and water vary too much in temperature. Is this still true
with modern b/w film emulsions?

I think you may mean 'reticulation': the emulsion crinkles and the
resulting picture looks a bit mosaic-like.

Not as big an issue as it was with modern films. Still an issue, though.
Keep all chemicals & water within a few degrees of each other. Before
reticulation there is grain clumping -- something else to be avoided.

Some photographers reticulate for arty-farty effects, Mortenson comes
to mind. Hot developer is the easiest way to cause the problem, possibly
an antique film - Efke & Co. - would help.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics, Photonics, Informatics.
Remove blanks to reply: n o lindan at ix . netcom . com

Reciprocity, (or more properly reciprocity departure) usual usage is for a
non-linear relationship between illumination and exposure in films at slower
speeds. In other words one second at f/5.6 no longer equals 4 seconds at
f/11 but the longer exposure instead might be 2 to 4 times more exposure.

There is also a non-linear relationship between developed density and
time/temp once you get outside the range of approximately 60-80 degrees F,
this is not normally called reciprocity.

And another term you may have come across, reticulation, caused by emulsions
cracking or moving off the base due to high processing temperatures outside
the manufacturer's recommended range.

--
darkroommike
"Blaine Owens" wrote in message
...
In the past reciprocity has been a concern when processing films if the
chemicals and water vary too much in temperature. Is this still true
with modern b/w film emulsions?

HI,

Is there a general standard reciprocity chart or is there a different
one for each film?

Cheers,
Bogdan

Mike King wrote:

Reciprocity, (or more properly reciprocity departure) usual usage is for a
non-linear relationship between illumination and exposure in films at slower
speeds. In other words one second at f/5.6 no longer equals 4 seconds at
f/11 but the longer exposure instead might be 2 to 4 times more exposure.

There is also a non-linear relationship between developed density and
time/temp once you get outside the range of approximately 60-80 degrees F,
this is not normally called reciprocity.

And another term you may have come across, reticulation, caused by emulsions
cracking or moving off the base due to high processing temperatures outside
the manufacturer's recommended range.


--
__________________________________________________ ________________
Bogdan Karasek
Montr‚al, Qu‚bec e-mail:
Canada

"Wovon man nicht sprechen kann, dar�ber muss man schweigen"
"What we cannot speak about we must pass over in silence"
Ludwig Wittgenstein
__________________________________________________ ______________

You can make generalizations but each film is different, classic example:
TMax 100 has "better" reciprocity than TMax 400 and exposure compensation
will be shorter than with the normally higher speed film.

Most film makers publish reciprocity charts see for example:
http://www.kodak.com/global/en/profe...shortexposures

Easy enough to GOOGLE for the charts.

--
darkroommike

"Bogdan Karasek" wrote in message
...
HI,

Is there a general standard reciprocity chart or is there a different
one for each film?

Cheers,
Bogdan

Mike King wrote:

Reciprocity, (or more properly reciprocity departure) usual usage is for
a
non-linear relationship between illumination and exposure in films at
slower
speeds. In other words one second at f/5.6 no longer equals 4 seconds
at
f/11 but the longer exposure instead might be 2 to 4 times more
exposure.

There is also a non-linear relationship between developed density and
time/temp once you get outside the range of approximately 60-80 degrees
F,
this is not normally called reciprocity.

And another term you may have come across, reticulation, caused by
emulsions
cracking or moving off the base due to high processing temperatures
outside
the manufacturer's recommended range.


--
__________________________________________________ ________________
Bogdan Karasek
Montr‚al, Qu‚bec e-mail:
Canada

"Wovon man nicht sprechen kann, dar�ber muss man schweigen"
"What we cannot speak about we must pass over in silence"
Ludwig Wittgenstein
__________________________________________________ ______________

"Rod Smith" wrote in message
...
In article
,
(Blaine Owens) writes:

In the past reciprocity has been a concern when
processing films if the
chemicals and water vary too much in temperature. Is
this still true
with modern b/w film emulsions?

I suspect you're thinking of reticulation, not
reciprocity.

Snipping...
I think you are right. Also a good answer:-)


--
---
Richard Knoppow
Los Angeles, CA, USA

"Bogdan Karasek" wrote in message
...
HI,

Is there a general standard reciprocity chart or is there
a different one for each film?

Cheers,
Bogdan

Each one is different. Most manufacturers publish
reciprocity curves for both films and papers. Reciprocity
failure can cause not only exposure errors but color shifts
in color materials where the differenct layers reacact
differently. Kodak has a data sheet listing reciprocity
characteristics for its materials. Search their web site for
either reciprocity or E-31. http://www.kodak.com
Modern tabular grain films, like Kodak T-Max and Fuji
Acros, have much better reciprocity characteristics than
older films.


--
---
Richard Knoppow
Los Angeles, CA, USA