wrote:

Michael Gudzinowicz wrote:

wrote:

To the point, I've from the woods ONE roll of Delta 3200 to
develop. If ten minutes will do for a roll of HP5+ how many
minutes should I give the Delta? Or, by what factor should
I multiply the ten minutes? Dan

If you're trying to estimate a time for Delta 3200 based on a
known HP5+ time for a certain temperature, EI and CI, check
the Ilford film PDF's for both films and the developer you
intend to use.

The developer is ACU-1 and the films are the HP5+ and
Delta 3200. ACU-1 and the Delta is not a combination listed
in the Massive Chart. For a K I'll check the two films in D-76
and likely another developer or two in which both films
have been processed. Dan

If some data was available, I guess you wouldn't have asked.

I assume that you don't have more D3200 to run a clip test,
or a developer for which Ilford provides data.

There is a "constant" called the Waller coefficient which varies
markedly for different developers, but is fairly "constant" for
similar types of films. The coefficient is the ratio of the required or
total development time to the time of emergence of the image. That
observation is the basis of "factorial" development of paper.

And of course, we don't know the value for Acu1, and apparently
there's no D3200 film to waste. What I would do, would be to clip
a section of leader from HP5+ or the last 1/4" of the tail of 120
film, and reroll it. Expose to light and develop in a tray and note
the emergence time for a light gray image. I'd let development
continue for the same period of time (2X emergence time total), stop
and fix the HP5+. The film should be underdeveloped to a grey tone
rather than opaque black.

Divide your known development time by the time to emergence, and
use this as your constant. Get a scrap of D3200 film from the leader or
non-image area of 120, in light determine the emergence time, and
stop at 2x that time as with HP5+. Compare the fixed films and see
if the densities are the same. If they are identical, use the factor to
calculate a D3200 development time. If they are "close" (within 10% using a
densitometer), use the optical density ratios to tweak the time calculated with
the factor. If they are no where near agreement, try again with scraps you've saved.

This is a rather oblique approach, but it avoids the comparison of
two films in different developers where the ratios of development times
will differ. In those situations, the ratio of emergence times differs.

If you don't post, let me know where this goes by email.