re: pyro and cyano
Good Morning!! One other point: an offlist convo got me thinking--the question was this: does cyanotype have any contrast controls that can be utilized to match the contrast range of the process to the contrast range of the negative, such as is possible in pt/pd? With pt/pd you've got humidity and NA2 or whatnot...and also the fact that pt/pd is a DOP process allows that gorgeous tonal range that goes up to maybe 10 stops or perhaps more. With digital negs you adjust the curve to suit the process, but with film negs... I have SOME methods of "increasing tonal range" in cyanotype--adding a drop of 40% citric acid to each 2ml sensitizer before coating. Or using a citric acid bath or uisng vinegar in the water wash...the latter two I have abandoned because years ago as I reported on the list all it seemed to do was mordant blue dye all over my bathtub. My guess is this, though--that since cyanotype is a shorter scale process than silver--6 stops seems about max, and even with these acid methods it ain't gonna get much better--the extended range of the pyro neg is probably not suitable for cyanotype as it is for other processes that have longer tonal ranges, unless one were to contract the tonal range of the pyro neg to match cyano--or have subject matter that is tonally contracted anyway. BUT, and this is my question: does anyone know the maximum DR possible in a pyro neg? I do not have a UV densitometer. And, from memory (which obviously doesn't serve me too well so please answer this, too) a film negative can actually record up to 13 stops of info, pt/pd about 10, BW paper about 7, and cyano about 6...you get my point perhaps. OK, I think that covers all I wanted to ask/say. I have put my cyano visual at the URL below and I also put one more image there--students cannot seem to remember that yellow seems pale but it is the densest ink set (learned from PDN) and magenta the least dense, so I made a silly visual of large ink "dots" side by side and printed them in platinum to show how much light these dots of ink hold back in comparison. It might be a helpful visual for someone. http://christinaanderson.visualserver.com/Text_page.cfm?pID=2448 OHHH man do I need to get back to work, this is too fun posting all these silly visuals, and hopefully someone will benefit except me :) Chris __________________ Christina Z. Anderson http://christinaZanderson.com/ __________________
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