[rollei_list] Re: Plus X -PX 125- and Microdol X discontinued
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Thu, 18 Feb 2010 03:34:09 -0800
----- Original Message -----
From: "Mark Rabiner" <mark@xxxxxxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Wednesday, February 17, 2010 8:24 AM
Subject: [rollei_list] Re: Plus X -PX 125- and Microdol X
discontinued
My personal preference in printing is for absolutely no
noticeable grain in
the print, which I can accomplish through a Leica, HC110
and an 11 X 14
print maximum.
Marvin.
The only problem with developer dilution combinations
which give you fine
grain is they give you poor acutance. There is some
degrading of image.
Usually form sulfite eating away at your grain. One not
getting their cake
and getting to eat it too.
From a Rollei medium format neg grain should not be an
issue with acutance
developers in any size you're likely to print.
I'd try some acutance developers you might find the
clarity might overweigh
some slight notability of grain you might experience that
you were not used
to. It will be very faint but sharp and regular. Not mush
grain which has
been eaten away at by sodium sulfite.
With high sulfite developer dilutions one wonders what the
point is
obsessing over Zeiss vs. Schneider vs. anything glass
you're not going to be
experiencing the highest common denominator.
[Rabs]
Mark William Rabiner
I really need to get into this. The solvent action in
developers with a lot of it does not dissolve any of the
developed silver grains. What it does is to change the
morphology of the grains and their distribution in the
emulsion. Developers like D-76 or even D-25 do not affect
the resolution of the film. The effect on acutance is due to
the prevention of reaction products of development from
affecting the rate of development at sharp discontinuities
of the image. Some reaction products act as restrainers.
Metol is such a developing agent. Some act as accelerators,
for instance those of hyroquinone. In fact, the accelerating
action of hydroquinone reaction products is one reason it is
used in very high contrast developers. These reaction
products are proportional to the image density. So, where
there is a sharp demarcation between a high and low density
the reaction products in the immediate vicinity tend to
either restrain the development on the low side or to
accelerate it on the high side. In some developers both
happen so that there is a very localized increase in
contrast around the demarcation. The scale of this effect
depends on the rate of diffusion of the reaction products in
the emulsion and are fixed in size so that they make much
difference for small than large negatives.
Sulfite tends to prevent oxidation of the developing
agents, which are reducers and tend to oxidize easily. It is
the oxidation which occurs during and because of development
which produces the reaction products and thus the acutance
effect. The more sulfite the less the reaction products
produced or the faster they recombine. This effect of
sulfite is separate from its effects as a _halide_ solvent.
It has a second grain reducing effect, namely the "salt"
effect which helps to prevent emulsion swelling and the
attendant grain migration which results in grain clumping.
Modern emulsions do not swell much so the salt effect is
less than in the past. Other salts in the developer also
contribute to the salt effect including carbonates and boron
compounds like borax.
The effect of the solvent action is complex. It changes
the way the metallic silver particles are formed out of the
halide crystals. In a low solvent developer the silver
crystals tend to be the same shape as the original halide
ones. In a high solvent developer they tend to form as very
fine filiments which have higher covering power than the
simple crystals. Depending on the amount of solvent it can
also increase or reduce film speed. At moderate
concentrations, as in D-76, the solvent can increase speed
somewhat because it etches the surface of the halide
crystals and makes more development centers available to the
developer. If the solvent effect is increased, as it is in
D-25 by its low activity, it can actually destroy some of
the development centers resulting in some loss of speed. The
solvent action does not account for speed or grain by
itself: the developing agent also has an effect. For
instance, paraphenylenediamine, which became popular in the
early 1930s for 35mm film produces extremely fine grain but
looses as much as 5 or more stops of speed if used alone.
PPD is an effective halide solvent and this may account for
its loss of speed, at least in part. Orthophenelynediamine,
which is not a developing agent, was used in some fine grain
developers primarily as a solvent where something else,
often Metol was used as the reducing agent. One of the
Windisch formulas contains it.
In any case it is certainly true that high sulfite
developers tend not to have acutance effects. But the main
cause of "mushiness" is the lack of resolution of the film,
the lens, or both. Keep in mind that to get good resolution
on an 8x10 print from a 35mm negative requires something on
the order of 60 lp/mm on the negative at reasonably high
contrast. That is hard to do considering both film and lens
have to have about double this value. This is one reason
that getting results from 35mm that are comparable to almost
anything larger is very difficult.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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