[pure-silver] Re: Good acutance and tonality for HP5+ 120 format
- From: Robert Randall <bob@xxxxxxxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Mon, 18 May 2009 09:49:36 -0500
In my search for the perfect film/developer combination for digital out put
on a film recorder, I must have made family of curves tests on at least 20
different films with all manner of developers.Old style films such as Tri-X,
Ektapan, HP5, etc, showed absolutely no tendency toward linearity in their
curves.
For my purposes, a straight line curve was a desirable trait, so you can bet
I was on the lookout for it. No developer that I used enhanced the
linearity of any of the old style emulsions. I don't have access to my test
data, so I can't be certain of my next statement, but as I recall, if a
particular film was noted for having a long shoulder, the developer wasn't
going to change that characteristic very much.
The most linear curve came from tab grain films such as Tmax, which is
ultimately what I wound up using. It has a very short toe and no shoulder
whatsoever. Oddly, as I recall, it's toe was even shorter in Xtol 1:1 than
it was in Tmax RS developer.
A by product of Xtol development, no matter the dilution, is an odd hump
near the mid-tone, which makes the mid-tone brighter and more difficult to
separate from the highlight, but easier to separate from the shoulder. This
oddity occurred on every film I tested, whether it was tab grain or
traditional film, although the effect on tab grain films was minor. I
contacted Dickerson and Zawadski, the couple that invented Xtol, and they
confirmed the phenomenon. They also confirmed they had no real explanation
for the hump.
As a point of curiosity, I have a question for all of you regarding HP5. In
all my tests, it was the single worst performing film available. The grain
is horrible, the emulsion makes the film inherently soft, and the only
acutance to speak of is a measurable increase in the visibility of the
grain. Mind you, this is based on testing and not usage, so my question is;
why do any of you use it? What feedback do you receive from the final image
that causes you to like the film?
Bob Randall
On 5/18/09 6:13 AM, "Jean-David Beyer" <jeandavid8@xxxxxxxxxxx> wrote:
> Peter Badcock wrote:
>> Hi folks,
>>
>> I am about to develop a roll of HP5+ (120 format) and I need you to help
>> me settle on a choice of developer. So Initially, here are my
>> observations and requirements:
>>
>> 1. My scene contains a landscape shot with a Subject Brightness Range
>> (SBR) of about 8-9 stops.
>> 2. I would like use a developer which will provide very good acutance.
>> 3. I think I would like linear tonal separation over the SBR of the
>> scene (let me know if that requirement will not result in
>> subjectively pleasing results).
>> 4. I'm not too fussed about minor to moderate differences in grain
>> size because print size will be no more than about 11x14inches.
>> 5. I think I have narrowed down my developer choice to either
>> Perceptol or XTOL.
>>
>>
>> Can people help me decide between those two developers which will
>> optimise points 2 and 3 above? (Or even offer another suggestion - e.g.
>> I also have some 510-pyro to make up).
>>
> The nearest I can help you with is #3, because I have never used HP5+ or
> Perceptol.
> But for point 3, I have found that using Xtol 1+1 on TMax 100 and TMax 400
> at 75F is that the straightest D/H curve I have ever seen. You have to
> expose it enough, however, because it goes straight down and if you
> underexpose, you will have no detail at all in the shadows (very short toe),
> but as long as you are over that point, the shadow detail is very good.
>
> Under my conditions, I expose TMax 400 at EI 200 for these results.
>
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