[pure-silver] Re: hp5+ at 125 development times
- From: Tim Daneliuk <tundra@xxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 05 Oct 2009 12:15:31 -0500
Jean-David Beyer wrote:
> Shannon Stoney wrote:
>> Hi, I accidentally shot some hp5+ at 125, because I thought I had fp4+
>> in my camera.
>>
>> By about what percentage should I reduce the development times? I
>> normally develop it in DDX 1+4 for about 11 minutes. I was thinking
>> maybe...9 minutes?
>>
> I would not shorten the times at all. Development time affects the
> contrast of the negative. Exposure affects the density. So if you would
> develop normally, then continue to do that. The negatives will take
> longer to print and you will probably get a bit more shadow detail than
> you are used to.
>
> If you reduce the development time, the contrast will be lower than you
> probably want.
>
Shannon, Jean-David -
I'm not sure I quite agree. Here's why:
- Changing development *mostly* affects the upper midtones and highlights by
changing the gamma (contrast) of the H/D curve. But it does somewhat
change effective film speed because it moves the
threshold of where the film begins to respond to very low levels up
light up- and down a bit (the left end of the H/D curve). The more
extreme the development change, the more the effective ASA changes.
- If you have accurate shutters, light meters, thermometers, and
consistent/clean
water for your chemistry, my consistent experience - verified both in practice
and with a densitometer - is that pretty much every film I've used with pretty
much any developer *is rated a full stop too fast*. For ASA 400 films, I
expose
them at 200 (under normal contrast conditions) and then *underdevelop* about
20% from the published recommendation for that film/developer combo.
(This varies a bit by developer, but as a rough estimate, it's a pretty
good start assuming, as I said, that your exposure and measurement chain
is clean.) The lowered ASA adds more details to the shadows. The decreased
development keeps the highlights from blowing out.
So, having said that, let's inspect Shannon's situation:
HP4 is nominally rated at ASA 400
Shannon's normal development time is 11 min
If you believe what I said above, the real ASA is more like 200 and proper
development time is more like 8.8 minutes.
But ... Shannon exposed at ASA 125, almost a full stop more light than my
nominal.
(In zone system terms it's about N-1 - something you do when you need to
contract
the contrast range a bit when it's too long to fit on the film.) So further
underdevelopment (from my nominal) would be indicated. It's hard to know how
much, but I'd guess another 15% or so would be in order so:
11 * .65 = 7.15 min
This should result in negatives with excellent shadow detail and a
somewhat compressed tonal range (lower gamma or contrast). If, OTOH,
Shannon develops for the full 11 min, the shadow detail will be
strong, but the highlights will either be really difficult to print
(very, very long exposure times up to and beyond the reciprocity
failure of the paper) and/or the highlights will be blown out
completely to bright white with no detail at all.
P.S. These estimates of reduced ASA and development times do vary
somewhat even for a particular film because different formats have a
different film base + fog baseline. This is because 35mm, especially,
uses a different base than 120 or 4x5. Still, when I don't have time
to test a new film/dev combo, "Cut the ASA in half, and underdevelop
20%" has always given me very good results.
P.P.S. It is a *really* good idea to do some "personal ASA" testing
that will take into account YOUR thermometer, shutter, light meter,
agitation style, water composition, and so forth. Both Ansel Adams
describes this in great detail, but a very good crash course can be
found in Fred Picker's introduction to Zone System. I'm not one that
believes you need to measure things out to 0.000001%, but getting
a basic personal ASA and development time calibration done is really
helpful.
P.P.P.S The calibration above does mean that you need access to a
transmission densitometer. I have one and will do it for anyone
that needs it done for $10 per neg - providing both FB+B and absolute
density - plus shipping. I am not in this business, so I reserve the
right to not spend the rest of my life testing everyone's negs - I
have my own pictures to make :) IOW, I do this only if/when I have
time ...
--
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Tim Daneliuk tundra@xxxxxxxxxxxxxx
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