Re: Film Speed and Negative Development (OT)

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From: Phillip Murphy (pmurf@bellsouth.net)
Date: 04/08/03-08:23:53 PM Z


The off-the-shelf solution for increasing the appearance of film speed
without
increasing contrast in the past has been with Acufine or Diafine
developers.
( I believe Crawley's FX developers are an attempt to substitute those
developers)

One of the methods I've practiced successfully for truly increasing
certain film stock's
effective sensitivity is with gas (Hypering) hypersensitization. There
is a range of
methods and apparatus involved depending on the chemistry and
technique. Anyone interested
in actually increasing film sensitivity can Google the Astrophotography
sites for information.

It's questionable how practical this would be for someone. Like owning
a Noctilux lens. : )

-Phillip

Richard Knoppow wrote:

> ----- Original Message -----
> From: "Scott Wainer" <smwbmp@starpower.net>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Monday, April 07, 2003 8:11 PM
> Subject: Film Speed and Negative Development
>
> > Hi all,
> >
> > Having just bought some Arista Pro 125 (aka, Ilford FP4+)
> I decided to run
> > some film speed tests. I tried Crawley's FX-37 developer,
> Kodak Xtol, and
> > D-76/ID 11 and ran into what I consider a problem. All of
> the developers
> > indicated an EI of about 12-25 with standard development
> using a B+W
> > densitometer. Increasing dilution and development effected
> the highlights
> > but not the shadows; the EI still remained 12-25. The
> reason for testing
> > Crawley's FX-37 developer and Kodak Xtol was that they are
> listed as
> > increasing speed and sharpness with greater dilutions. I
> also tried Sandy's
> > Pyrocat-HD developer and found that the film did not
> record anything below
> > zone IV. All chemistry was mixed from raw chemicals just
> prior to
> > development. I thought it might be possible that my 35mm
> camera's meter was
> > off so I took readings with a spot meter and got the same
> readings.
> >
> > Has anyone encountered this problem before? Could my
> chemicals have gone bad
> > in less than six months? Any ideas on how I can get the
> film speed closer
> > the manufacturer's rating of 125?
> >
> > Thanks in advance,
> >
> > Scott
> > smwbmp@starpower.net
> >
> I've read the reply where you describe your technique of
> measuring.
> To start off, the method specifiec by the ISO is not an
> in-camera method. It requires making exposures on a
> sensitometer meeting certain specifications, which include
> the color of the light source. The film is then developed to
> a specified contrast although its not stated as a gamma
> value but rather as a density range for a given exposure
> range. The measurement is made at a density value of 0.1
> over the fog level plus the base density, which can be
> considerable for 35mm films.
> The speed varies with the developer. The current ISO
> standard does not specify a developer as older versions did.
> One can now use any developer but it must be stated along
> with the speed.
> Variations in speed from developer type have a range of
> approximately +/- 3/4 stop. Developers like Microdol-X, tend
> to loose speed, Phenidone based developers tend to gain
> speed. Developers like D-76 and D-23 will deliver about the
> ISO rated speed.
> Contrast is important. The ISO standard is based on an
> effective contrast index about right for diffusion enlarging
> or contact printing. Developing to a lower contrast, as for
> a condenser enlarger for instance, will result in a lower
> speed.
> Ilford claims not to use the ISO method. They don't state
> what method they use but I suspect its a variation of the
> ISO method but using a contrast value half way between
> diffusion and condenser values.
> The ISO method does not include a safety factor so
> predicted exposures are about the minimum that will result
> in adequate shadow detail. Since nearly all films have
> tremendous overexposure latitude (10 or 12 stops for most)
> increasing exposure from that given by the ISO speed can
> result in better negatives in some cases.
> Measuring speed using a camera introduces a lot of
> variables and sources of error. For one thing the flare of
> the system (lens flare plus flare from the camera itself)
> changes the effective curve shape of the film, lowering the
> contrast of the toe region. Since the target density is very
> low it will be significantly affected.
> Valid speed measurements are not trivial.
> OTOH, because of the latitude of the film "accurate"
> exposure is really not necessary or even meaningful. The
> minimum exposure must be such as to place the shadows which
> are to print with detail far enough up the curve to be in a
> region with reasonably high contrast. L.A.Jones of Kodak
> came up with 0.3 of the straight line gamma as the minimum
> point, and this was used as the basis for the old Kodak
> Speed method. At the same time the brightest objects in the
> image, which are to print with some detail, must not be of
> such high density as to be beyond the range of the printing
> method to reproduce. This is a complicated way of saying
> that the film must be developed to a contrast suitable for
> the subject and printing material. Zone system stuff
> although you can achieve it more simply than using the full
> Zone System.
> As far is increasing the real speed of film, i.e., the
> ability to record lower minimum exposure for a given
> contrast, it can't really be done. Phenidone based
> developers, like Xtol, T-Max and T-Max-RS, Microphen, will
> yeild about 1/2 to 3/4 stop increase over standard
> developers, like D-76 or D-23, but that's the limit. Pushing
> means increasing overall contrast to get the toe contrast
> up. The result may be to make toe exposures more printible,
> but at the price of making the negatives very high contrast.
> If the entire exposure is in the toe area the approach
> works, but where there are also bright objects in the image
> they will become very hard to print requiring lots of
> burning or masking.
> so called compensating developers, can be helpful in
> recording very high contrast objects by compressing the
> values of the brightest parts of the image, but in general,
> do not raise toe contrast.
> FWIW, Aristo definitely IS Ilford film. I've even bought
> rolls that had Ilford sticky lables on the rolls! Other
> materials sold by Freestyle under their house brand may not
> be Ilford, at least some of the paper is made by Kentmere
> and possibly others.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@ix.netcom.com


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