Im trying to figure out how to shoot to use POP and they recommend a film density of 2...I shoot tri-x 320, is this just a matter of adjusting the exposure time and processing? I imagine if the POP is graded at 0 or 00 that the negative will have to be pretty contrasty, the only way I know to increase contrast is to develop longer, am I on the right track?
They're really after a certain contrast level, not a certain exposure. Since POP and similar processes are "self-masking" -- that is, the density is produced during exposure, which partially blocks exposure in denser regions -- they require negatives with much higher contrast that modern developing-out processes like silver gelatin contact printing or enlargement. All you need to do is find the correct amount of N+ development to produce good prints on POP, and (if desired) adjust your exposure to compensate the small film speed increase you'll see from increasing development. I'd start by increasing your normal development 50%, ideally on a single sheet, and make a test print or two, then adjust again -- 2-3 tests of this sort and you should get it dialed in.
BTW, negatives with this level of contrast as also preferred for other processes where a UV-blocking image forms during exposure, such as salt prints, van Dyke brown prints, and platinum/palladium, though there is some variation on exact level that's considered optimum for each process.
If a contact print at arm's length is too small to see, you need a bigger camera. :D
Time for density, agitation for contrast. Donald provided some excellent advice.
Prints on POP are best with a density range that is difficult to get with "modern" emulsions. Staining developers seem to work best - the best results I've had, were with Agfa APX100 developed in Pyrocat-HD. Second best is FP4+ in the same developer, or developed "normally", then bleached and redeveloped in a simple Pyrogallol/potassium carbonate developer.
T-Max and Delta (in my experience) are unable to give sufficient density range regardless of development tricks.
Ole,
I have to disagree. In my testing, TMY is capable of considerable expansion development, even with a paper ES of 2. See attached curves.
Jay
Last edited by Jay DeFehr; 6-Jun-2006 at 14:07. Reason: image didn't load
You need negatives with a DR of about 2.0 or slightly higher to print with POP.Originally Posted by Ole Tjugen
Is that possible with modern emulsions? Defintely yes. If you are using TMAX-400 you can get sufficient contrast (assuming scenes of normal contrast) with about ten minutes of development in Pyrocat-HD 3:2:100 (rotary development at 70F). And with longer development times with this film you can get enough contrast even for very low contrast scenes (N+1 to N+2) for POP.
TRI-X 320 will also develop enough contrast for POP with scenes of normal contrast. You can get plenty of contrast for POP with a 5:3:100 diluition of Pyrocat-HD with about 12 minutes of development, again rotary at 70F. For scenes of less than normal contrast you need another film.
Sandy
Last edited by sanking; 6-Jun-2006 at 16:49.
I should add for clarity, that the curves I posted above were measured with a blue filter; I'm certain the contrast would be even greater as measured with UV.
Jay
Bonjour
I shoot 8x10 TRIX film at ISO 160.
In order to contact print on Centenial I stoped to develop with PMK and switched for Pyrocat which give more contrasted negatives.
As I only have a B&W densitometer, I can’t make significant mesurements on stained film, so I adjusted the process empirically.
I use an old 8x10 Ilford drum which was originaly devoted to cibachrome development, the drum work well and film back never stick inside.
The Ilford drum is very economical assuming that the minimum needed developer quantity is 75 ml, I choosed using 100ml for practical reasons. I roll the drum back and forth in a large tray filled with 1 cm of water at 21°C, very similar to BTZS procedure.
I prewash the film 2 minutes and then develop with 2ml of pyro sol A plus 2 ml sol B diluted in 100ml of distilled water. I roll slowly 15 to 20 minutes at 21°C. depending from the subject contrast.Then stop bath and fix with 100 ml of rapid fixer.
My concern is about the rather long time development needed (frequently 17 minutes or more) and wonder if the very small pyrocat developer quantity used (2+2+100) is enough fort a 8x10 sheet.
I do not have any infos about the minimum quantity needed per surface unit.
jean claude
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