Alt process negative density methodsgreenspun.com : LUSENET : Large format photography : One Thread
When developing negatives for platinum/palladium and Carbon many develop a lot longer than "normal" to get the density needed. Some I know have changed a bit so they move their zone III exposure up to a zone V and then develop closer to a 'normal' time based on their silver negative density requirements. The rationale is that by moving everything a bit higher on the scale the density prints better with Carbon & some other alt processes that require very beefy negatives. Some say this gives better tonal range while retaining some detail in highlight areas for alt processes where just developing longer puts these highlights out of reach of even platinum printing. Anyone actually run some kind of calibrated testing to see if one or the other would be more reliable?
-- Dan Smith (email@example.com), May 20, 2001
I haven't done testing on that, but let me give you my impression on the process as you describe it.
I don't believe it will work as well as building a 'proper' negative. (Whhich we both know there is no such thing). If you meter and then place zone III at zone V, you are overexposing the film substantially. This will give you solid shadow detail and a dense negative that you will have to print through (be prepared to wait for a long time while printing). However, you have no knowledge of where the highlights are going to fall with this method. What happens to the highlights when you go two over zone VII or VIII? You have to know where the film is going to place the highlights to get a reliably consistant result. That's what processing for i.4 or 1.6 DR will do for you.
This method sounds similar to what Carl Weese does, and it works for him, so it could work for you also. However, I would note that I think the real benefit of this is that the negative has reliably consistant shadow density, not necessarily highlight density.
My feeling is that you have the tools to take light readings and build a negative to match the brightness range of the scene to the DR of the medium you plan to use. You might as well use them, and not leave the highlights to chance.
Just my thoughts...
-- Michael Mutmansky (firstname.lastname@example.org), May 21, 2001.
I stopped scientific testing of emulsions years ago, because I would rather make photos than tests. 8) I can offer you my observations based on experience. I have been printing Pt/Pd for about 10 years. You can make a beefy negative if you wish, but a negative that will print on a grade 1/2 VC silver paper will work in Pt/Pd, too. Added density to the negative increase printing time.
It seems that the straight line portion of the HD curve for "modern" films is a lot longer than earlier emulsions. You can expose a Zone III shadow at Zone V, but the highlight will occur at Zone XI rather than Zone IX. Because the straight line portion of the curve is longer, the difference between the density at Zone V and Zone XI will be the same as the density between Zones III and IX. The range is the same, the overall negative will be denser. If you keep your development at "normal" you will just add density, you will not change the relationship among the zones. You will also add to printing time.
Some of the more scientifically posters may be able to give you the quantitative data you add. I know what works in my darkroom.
-- Joe Lipka (JoeLipka@compuserve.com), May 21, 2001.
It may also depend on which film you are shooting. My recollection from earlier posts is that Dan uses Ilford and Arista (which is said to be the same thing). My experience with the 400 speed version of those films (admittedly limited) is that, unlike TXP for example, they have a very definite shoulder, making it difficult enough to get a sufficient amount of contrast for some of these alt. printing methods. (I use Ziatype which requires a very contrasty negative--more so than even tradition Pt/Pd.) I would be concerned that overexposing would futher compress higher values into the shoulder making the negative dense but too flat.
-- Chris Patti (email@example.com), May 21, 2001.
Dan, you might want to contact Sandy King, a long-time carbon printer. He posts regularly on the Alt-Process mailing list, and will be at the Alternative Process International Symposium in Santa Fe in July. He has invented his own developer (Pyrocat-HD), and for most of his alt-process work he doubles the amount of accellerator (solution B). Pyrocat-HD was designed as a non-toxic replacement for PMK pyro, and I have found them nearly interchangeable, so you might also try PMK with double solution B.
-- Ed Buffaloe (firstname.lastname@example.org), May 23, 2001.