"Digitaltruth" wrote in message
...
The Massive Dev Chart is more reliable than the published
data sheets
released by manufacturers. Why? Because it incorporates
the official
information that you will find in the manufacturer's data
sheets, AND
it includes additional user submissions and amendments.
I've spent 15
years collating and editing this data, which is a lot more
time than
the manufacturers spend on it.

While some manufacturers, most notably Ilford and Fuji,
provide
excellent data based on their own in-house analysis, many
other
manufacturers are far less thorough. In fact, there are
several
official data sheets currently being published which
include data from
the Massive Dev Chart as the primary source, even though I
doubt the
manufacturers have ever tested it themselves.

One of the recurrent questions about the Massive Dev Chart
is why
Ilford's published times for developing film in Kodak D-76
are only
included if they are the same as the published times for
ID-11. The
reason for this is because the chemical composition of
these two
developers is almost identical. In fact, the difference is
sufficiently small so as to be negligible for all intents
and
purposes. Ilford's data for its own products is highly
reliable, so
when there is a significant variance between times for
third-party
chemicals such as D-76, then it is safe to assume that the
testing
procedure was different and should not be relied on if it
does not
match that of ID-11.

Perceptol and Microdol-X are not the same developer,
although they
have similar characteristics. Different times are
required, so you
should use the data for each developer in The Massive Dev
Chart to
provide the required starting point.

If you study official data sheets you will notice that
manufacturers
often update the times even though no changes have been
made to their
products. Conversely, Kodak changed many times when they
modified the
film base on several products a few years back, but other
published
studies showed that the original times were more accurate.
You can
also see that, famously in the case of Agfa, they release
different
data in different countries. Trusting something just
because it is
printed by the manufacturer is does not offer any
guarantee of
accuracy.

The most important part of any issues regarding accuracy
of
development times is to understand that ALL times are
starting point
recommendations, regardless of the source, and it is up to
the
individual user to use these starting points to determine
the optimum
development in relation to subject contrast, print
contrast and
enlarging equipment.

--Jon Mided

http://www.digitaltruth.com

If you check the MSDS you will find that Microdol-X and
Perceptol are essentially identical. I say essentially
because both manuacturers probably have additions in the
form of sequestering agents that do not show up in MSDS.
Also, Kodak has patented method of preparing some of the
ingredients they use. The published formulas for D-76 and
ID-11 are the same but the packaged developers may be
different. The MSDS for D-76 shows it to be the buffered
formula similar to the published D-76d. Packaged ID-11 may
also be buffered but no buffering agent shows up in the
MSDS.
Manufacturers' data is generated by use of proper
sensitometry, at least its supposed to be and I think Kodak
and Ilford data are reliable. One difference between the two
is that some time ago Ilford stopped using the ISO method to
rate film. The ISO standard is correct for a contrast index
about right for diffusion enlarging and contact printing.
When lower contrast is desired for condenser enlargers the
development must be adjusted with a consequent change in
effective film speed. Ilford appears to use a contrast index
mid-way between condenser and diffusion values. This results
in a slight lowering of effective speed when the film is
developed to diffusion contrast and accounts for the
differnce in developing times for Ilford film given by
Ilford and some others.


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