"Martin J" <maja@[EMAIL PROTECTED]
> wrote in message
news:fvf0q6$1odb$2@[EMAIL PROTECTED]
> krishnananda <k@[EMAIL PROTECTED]
> wrote:
>> For the past ten years or so I have been using HP5+ as my
>> primary B/W
>> emulsion, having found it to be contrastier than Tri-X,
>> which I had used
>> for the previous 20 years.
>>
>> Now I'm finding that Tri-X is more contrasty -- to my
>> eye -- than HP5+.
>> Has anyone else noticed this? Some variables are taken
>> care of: same
>> lab, same cameras/lenses, usually same developing batch,
>> side-by-side
>> comparison of the negs and contacts. Tri-X has a purple
>> mask and HP5+
>> doesn't, but I'm not sure what difference that makes.
>
>
> Differences in developing-time or -temperature?
>
> You can trim any film to any contrast index you like by
> developing
> it longer or shorter (and adjusting exposure). If HP5+ is
> too contrasty,
> shorten your development by 15%... (for a first
> approximation).
>
> You typically can't adjust curve shape by changing
> developers and/or
> times, a straight or s-type density curve is built into
> the emulsion. It
> is possible (by a very low margin) to get a slight
> shoulder in a density
> curve by using twobath-development, but I haven't found
> that too useful.
>
> Martin
>
I will add that Tri-X should not have a purple cast.
This is due to either underfixing or lack of washing. Try
refixing these negatives in _fresh_ fixer. The color is
either from residual sensitizing dye bonded to unfixed
halide or to residual anti-halation dye. The latter should
be decolorized by the sulfite in the developer or fixer.
Re-fixing should get rid of either dye. If there is still a
slight color use a sulfite wash aid like Kodak Hypo Clearing
Agent as directed. That will usually remove any residual
color.
The only films with any sort of base density are 35mm
B&W films which have a pigment in the support to prevent the
conduction of light through them when one end is exposed to
the light, as is common for 35mm. This pigment is usually
either neutral gray or slightly blue. It can not be removed.
--
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]
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