Kodak published a formula for a variable contrast paper developer, D-64. This was said to give a certain amount of contrast control for a single paper grade. There is also a formula from Adox, E-15. This technique fell out of use when variable contrast papers became widely available. The contrast range that these formulas provided was probably about 1 paper grade or less. Jerry -----Original Message----- From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx]On Behalf Of DarkroomMagic Sent: Monday, October 18, 2004 6:58 PM To: PureSilverNew Subject: [pure-silver] Re: Polycontrast Paper Performance / Cold lite Richard First, RC papers are definitely developed to completion, no argument there. However, I don't think FB papers are. FB papers increase in contrast with development time. Richard Henry's book shows this on page 89 in the second edition. They do, because Dmax is reached quickly (within 1 min) while highlights increase in print density with development time. This is useful until the highlights start to fog at about 8 minutes or more. This is also why factorial development works with FB papers as it creates full Dmax at any factor from 4 to 8. Second, I don't know if developers affect paper contrast for sure. My one-time experience with Selectol is too far into the past, and I didn't keep good records back then. I remember it being slightly softer. This was measured and not just a subjective observation, but again, I don't have any records of this. AA claims that it does, and Richard Henry saw no evidence in diluted Dektol, which could simply means that 'Dektol is Dektol' at any dilution. However, if a developer does not reach the papers max black or needs more time to do so, the characteristic curve may be affected in the shoulder region, leveling off. If we measure paper contrast from 0.04 above 'base & fog' to 90% Dmax, it may make for a softer paper. I will test in the future, but I doubt that a developer not reaching highest possible paper Dmax will follow one given paper characteristic curve just to stop dead in its tracks. Until then, I will assume that paper, just like film, has developer depending characteristic curves. Regards Ralph W. Lambrecht On 10/18/04 11:25 PM, "Richard Knoppow" <dickburk@xxxxxxxxxxxxx> wrote: > > ----- Original Message ----- > From: "DarkroomMagic" <info@xxxxxxxxxxxxxxxx> > To: "PureSilverNew" <pure-silver@xxxxxxxxxxxxx> > Sent: Monday, October 18, 2004 10:36 AM > Subject: [pure-silver] Re: Polycontrast Paper Performance / > Cold lite > > >> My one-time experience with Selectol Soft brought paper >> contrast down by >> less than 1/2 grade. Since I get similar or better results >> with changing the >> factor of factorial development (FB papers only, of >> course), I gave up on >> soft developers and the increased darkroom complexity they >> bring. >> >> >> >> >> >> Regards >> >> >> >> Ralph W. Lambrecht >> >> > I am puzzled by how the developer can affect paper > contrast at all. Prints are developed to "completion", that > is to the highest contrast the material is capable of. > Negative film is not developed to completion but rather to > some desired contrast. Paper contrast would also vary > somewhat if developed less but the main difference would be > a loss of density in the shadows. What experimental data > shows is that once exposure and development are sufficient > to obtain full black from the paper that variation in > development time simply moves the characteristic curve > horizontally along the graph but does not change its slope > significantly. Of course, this varies with the paper. A "low > contrast" developer like Selectol-Soft or Agfa 120 develops > more slowly than a more active developer like Dektol, but, > unless there is some selection of grains by the developer, > the contrast should be the same provided the same shadow > density is reached. > Perhaps there is something here I don't understand, if so > I would certainly like to. My understanding is that the > contrast of paper is determined mainly by the distribution > of sensitivity of the silver halide particles in the > emulsion. > I will define contrast as I understand it as being the > range of difference of exposure that results in a given > range of density in the image. In a print that density range > is from paper white to the maximum black the material is > capable of. > > --- > Richard Knoppow > Los Angeles, CA, USA > dickburk@xxxxxxxxxxxxx > > ============================================================================== > =============================== > To unsubscribe from this list, go to www.freelists.org and logon to your > account (the same e-mail address and password you set-up when you subscribed,) > and unsubscribe from there. ================================================================================ ============================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there. ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.