Film testing : Zone VIII

[d.s.]

Here are the specs.

Film: Bergger BPF 200.
Processed on rotory..Unicolor drum on Unicolor auto reversing base. All temps 68 degrees.
five min. water pre wet.
Dev: D-76 1:1, 13.5min.
water stop.
Fix.

Results:
Zone I came out at 200 ASA.
Then I processed a zone V and VIII negative together for the same time. (13.5 min.). Zone V was .66, net. Zone VIII was 1.39, net.

How much reduction (%) should I give my next batch of zone V and VIII negs to bring the zone VIII down to 1.30 net density? Should I worry about Zone V going down also, as it's already low? I use a diffusion enlarger. Omega D-2 w/ Zone VI head, Aristo V-54 lamp.

[Chris Gittins]

Try running tests at a few different development times, e.g., 15 min, 13.5 min, 12 min, and 10.5 min. You should be able to interpolate between points to get your desired OD.

For what it's worth, the few tests I've done with BPF200 + D76 produced very funky curves - significant shoulder in the highlights and not a smooth transition from the midtones.

Chris

[Joe Smigiel]

Just curious as to why you don't think the numbers you have are appropriate? Where are you getting the target numbers?

Have you tested the paper range? You might find the values you already have will work with the paper you plan to use. You've specified everything but the type and contrast grade of the paper you use and that IMO should be the first step in the testing procedure. Using a transmission stepwedge and running a paper test will let you know whether 0.66 net density will be OK for Zone V, etc. I usually target about 0.70 net for Zone V and 1.35 for Zone VIII when I'm doing regular silver prints on Ilford MG WT w/#2 filter & cold light, IIRC. (It has been awhile since I tested).

If you are concerned about holding Zone V higher and reducing Zone VIII, you might try altering the dilution of the developer instead of the time. That might change the curve shape for you.

[neil poulsen]

I don't worry too much about Zone V. I "might" check it.

I'm primarily concerned about Zone VIII or Zone III, shadows and highlights. Besided, you have two degrees of freedom of control: exposure and development time. This allows for controlling two variables. I prefer to control shadows and highlights.

[Richard Littlewood]

What about downrating to 100asa and reducing development. 13.5 mins sounds a long time to me!. I dont know how that particular film works, but I rate FP4 at 100 and rotary process in almost the same way as you (D-76, 1+1 68 degrees) and the maximum time I ever use is 7.75 mins. beyond that definate over- development sets in.

[d.s.]

Hi everyone, Thanks for the responses.

Chris, before I tested I shot a few sheets and found what others have stated. "empty shadows and blocked high lights.

Joe, I got these figures from A. Adams' The negative. These numbers worked well for me with Tri-X with the way I print. I print on Polymax fiber VC. I was hoping that when Zone VIII hit in the 1.25 to 1.35 range that I would have arrived at the proper developing time. 1.30 is the middle of that range. As it is, my Zone V is already at the bottom of it's range and I was concerned that when I reduce developing time to put Zone VIII in the sweet spot, then Zone V will be farther below it's place. I haven't had a chance to shoot and print a neg with things as they tested. Changing developer dilution is a thought which had not occured to me.

Neil, I'm with you on III and VIII. Zone V is my check point.

Richard, The manufacturers time is what I used as a starting point. My Zone I density came out at exactly .10 above B+F at their ASAof 200! I'll most likely retest at 160 ASA and reduce dev. time. Looking at the negs I shot before I tested, but developed for the same recomended times, The shadows are thin and the highlights are dense. So maybe more exposure and less developement is in order.

dee