How does choice of developer affect film speed?

Greetings. I have read many posts stating that a particular developer
could "give true film speed increase," and wonder what is meant by
this. What particularly confuses me is that the same photographers
shoot the film at the factory recommended ISO, so where does the speed
gain come into play?

Thank you for your time.

Short answer: It lowers the threshold of light, film requires to produce
detail in a given area. The amount of light needed to produce
a specific density value is thus lessened.



In article .com,
wrote:

Greetings. I have read many posts stating that a particular developer
could "give true film speed increase," and wonder what is meant by
this. What particularly confuses me is that the same photographers
shoot the film at the factory recommended ISO, so where does the speed
gain come into play?

Thank you for your time.

--
LF Website @ http://members.verizon.net/~gregoryblank

"To announce that there must be no criticism of the President,
or that we are to stand by the President, right or wrong,
is not only unpatriotic and servile, but is morally treasonable
to the American public."--Theodore Roosevelt, May 7, 1918

wrote:
Greetings. I have read many posts stating that a particular developer
could "give true film speed increase," and wonder what is meant by
this. What particularly confuses me is that the same photographers
shoot the film at the factory recommended ISO, so where does the speed
gain come into play?

Thank you for your time.

You have to think in terms of what it is that "speed" describes and why it's
useful with regards to photography, it's not just a number on the camera
dial (ok it is to some). Speed or the film's "rating" describes how the
manufacturer predicts the emulsion will react when struck by light and then
developed with a certain developer and the results then graphed
scientifically on an exposure scale (the H&D curve). All developers are not
created equal. You wouldn't except the same results processing two
identically exposed frames if one was developed in D-76 and the other in
coffee developer(Cafenol?) or horse **** for that matter. A developer can be
mixed at different strengths too, a strong developer is described as
"aggressive" a mild developer as "soft" or "gentle" think of this in
woodworking terms. If you used a coarse rasp to round off a corner you'd get
the job done quick but the wood would be rough, if you used 180 grit sand
paper to round off the corner it might take a while longer and the corner
would be smoother, which you choose depends on how much time you have and
what is acceptable in the finished product -- both are correct in their own
context. It's often advantageous to be able to shoot a subject with a faster
shutter speed, smaller aperture or longer lens. Carrying a tripod around
allows you to do quite a bit but isn't always practical. If you can bumped
up the shutter speed by declaring "this film is faster than that film" or
"this developer rates my film 1 or 2 stops faster" then you extend the range
of what you're able to do with the camera.
For example, if I shoot the same scene, let's say a grey card, and develop
a frame of TMAX 400 in developer "A" then measure (with a densitometer) how
dark (or dense) the image of card is on the negative and I get a value of
0.95 Then develop the same scene in developer "B" and the grey card measures
1.25 in density it means (or might mean) developer "B" is capable of
creating 1 stop more density on the negative than developer "A" because a
0.30 increment on the "photo density" scale (H&D curve) equals 1 stop. To
some degree "density" equates to data or usable "information" on the film so
a better developer means you have more negative to work with better detail
in the shadows might be one such benefit.

Thank you very much for the thoughtful reply and helpful analogies!
Looks like lots of testing in store for me. ;-)

Chris wrote:
Thank you very much for the thoughtful reply and
helpful analogies!
Looks like lots of testing in store for me.


How does choice of developer affect PAPER speed?
I've noticed that paper exposure varies with paper
developer.
I've a hunch that variance can be used to test
film developers using paper. Doing that would be a
lot quicker than shooting a roll of film for
each developer test. Dan

In article .com,
wrote:

Chris wrote:
Thank you very much for the thoughtful reply and
helpful analogies!
Looks like lots of testing in store for me.


How does choice of developer affect PAPER speed?
I've noticed that paper exposure varies with paper
developer.
I've a hunch that variance can be used to test
film developers using paper. Doing that would be a
lot quicker than shooting a roll of film for
each developer test. Dan

Well some developers and various dilutions produce more or less
contrast, contrast is relative to speed of the paper for a given
exposure and the other "same criteria".

The chemical make up of the emulsions between film and paper
I think are too dissimilar for that purpose.

--
LF Website @ http://members.verizon.net/~gregoryblank

"To announce that there must be no criticism of the President,
or that we are to stand by the President, right or wrong,
is not only unpatriotic and servile, but is morally treasonable
to the American public."--Theodore Roosevelt, May 7, 1918

Its helpful to know what ISO film speed is. The ISO has a standard
for measuring film speed which specifies the conditions of exposure and
development of the film. There was once a standard developer (actually
two) but the standard no longer requires these to be used. Any
developer can be used provided the developer is stated with the speed.
The standard is supposed to give a number that when set into the
computer of an exposure meter will give an exposure resuting in good
tonal rendition. The problem comes when the conditions of actual use
are not similar to those assumed by the standard.
One of the variables is the developer.
The standard specifies a range of exposure for the test and a range
of densities to be generated on the film. In effect, it specifies a
contrast index but it is indirect. If the film is developed to a
different contrast the effective speed will be different than given by
the standard.
Developers vary in their ability to select low values of latent
image. The range is not very large. D-76 is considered a standard for
"full" film speed for comparison to other developers. D-76 is not quite
optimum for maximising speed although close. Some Phenidone developers
are closer to being optimum, they give an increase in speed, that is, a
lower exposure will result in a given density on the film at the same
degree of development which is another way of saying contrast. So, when
one of these developers is used for the ISO test it will result in a
higher speed than if D-76 was used. Developers like Microphen, Xtol,
T-Max RS, fall into this class. Some developers destroy some of the
latent image or are not able to differentiate it from unexposed silver
halide crystals. These developers give a lower density for the same
value of exposure and development. Extra fine grain developers, like
Microdol-X or Ilford Perceptol, when used full strength, fall into this
class. A few developers fall in between somewhere.
The overall range of speed in comparison to D-76 is about plus or
minus 3/4 stop, not a lot.
Since the ISO standard effectively specifies a contrast index
develolping to a different contrast will affect the speed. The contrast
index of the standard is fairly high, suitable for diffusion printing.
If film is developed to a lower contrast, say for use in a condenser
enlarger, the speed will become less. In this case by about 3/4 stop.
The ISO speed is based on the idea that one should give film the
minimum exposure possible and still get good tonal rendition. The
reason is that grain and loss of sharpness increase with density. So,
there is a benefit in making negatives on the thin side, provided the
tonal rendition is good. Increasing exosure will sometimes result in
better tonal rendition with little increase in grain or loss of
sharpness especially with modern films which have thin, fine grain,
emulsions.
Because the ISO speed is designed to give minimum exposure, and
because it has little safety factor, film does not have much
underexposure latitude (room for exposure error) but usually has
enormous overexposure latitude.
Richard Knoppow
Los Angeles, CA, USA

wrote:

How does choice of developer affect PAPER speed?
I've noticed that paper exposure varies with paper
developer.
I've a hunch that variance can be used to test
film developers using paper. Doing that would be a
lot quicker than shooting a roll of film for
each developer test. Dan

The choice of paper developer does affect PAPER speed. I have not
specifically tested this, but I note that straight Amidol (Ansco 113)
developer requires about double the paper exposure than does D:72 1+2.

I think testing film developers using paper is a silly idea: the
conditions are completely different and the time and materials required to
ascertain the relationship for each and every combination of
film-developer-paper would surely exceed the effort and expense of testing
the film directly. Why make things more complicated than they need to be?

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Subject: How does choice of developer affect film speed?
From: Jean-David Beyer

I have not
specifically tested this, but I note that straight Amidol (Ansco 113)
developer requires about double the paper exposure than does D:72 1+2.

I think testing film developers using paper is a silly idea: the

Amidol is a paper developer.


Arthur Kramer
344th BG 494th BS
England, France, Belgium, Holland, Germany
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer

"Greetings. I have read many posts stating that a particular developer
could "give true film speed increase," and wonder what is meant by
this. What particularly confuses me is that the same photographers
shoot the film at the factory recommended ISO, so where does the speed
gain come into play?

Thank you for your time."

Certain developers give more or less speed, almost always balancing
other desirable qualities. This has been known for decades. It depends
on the formulation. The ISO speed is measured using a specified
developer, which is similar to D-76.