Archived posting to the Leica Users Group, 2001/06/12
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]My thanks go out to all who replied to my questions on this enlarger: Bob, Pascal, Mitch and Dan. Regards, Greg J. Lorenzo Calgary, Alberta Dan Post wrote: > > Greg- > If you are using the color head to print variable contrast paper, allow me > to make a suggestion. I'll preface my remarks by saying that having had a > step-tablet, the same one for twenty five years or so, really is not that > major an expense, even if you buy the outrageously priced Kodak version, and > I have seen them offered on the internet for as little as about $20 for a 21 > step tablet. I also made the investment in a used Beseler Color Analyser, > some which I have bought for as little as $50 dollars, and then sold to > friends who I taught split printing to (at cost, by the way!!) > > If you use Ilford paper, they have a 'guide' where the approximate steps of > contrast are shown with the approximate settings of the color head. As you > note, I said 'approximate' since the color heads' calibration is anything > but exact, and you would need a densitometer- or enlarging meter! to > determaine with any accuracy the true density of any filter setting. > > What I did was to use each of the settings given, and exposed a strip of > paper with a step tablet on top using each 'grade' of filtration, > developing, then seeing what the actual contrast grade turned out to be. > > Since a step tablet like the one I use is divided into 21 steps of density, > eachone about .15 absolute optical density more dense than the previous, it > gives a fairly wide range of possibilities. IF you think of it as a negative > developed to a contrast index of .5 then each step represents one stop of > difference in theoretical illumnation of a scene- and could be considered a > 'perfect' negative since it captures all the possible tones you might > encounter in a one strip. > > So if you find that there are seven bars of gray on your test strip, then > you know that the absolute range of that particular filter setting is seven > times .15, or .75. This translates into a density range of .75- from the > darkest printable shadow to the lightest detectable highlight! > > Simply adjusting the filtration either more yellow or more magenta will > alter the overall 'grade' and you can very easily adjust the filtration to > give you the exact 'grade you want. You can plot several settings on a chart > and extraploate to find the exact contrast grade you want. > > Cyan is very little used, but if you want to use it, it makes little > difference- Cyan and Yellow makes a green light, typically you think of it > as about 562nm wavelength, and the Cyan and Magenta make Blue- the exact > wavelength escapes me, but I think about 450nm. The low contrast emulsion is > senitive to the green, and the high contrast emulsion is sensitive to the > blue. Varying the two will make the VC paper respond in almost an infinite > number of possible grades within the range of its sensitivity. > > Usually, I can count on Ilford Multigrade to give me a range of three steps > at the highest contrast setting to about eleven with the lowest- that means > that a negative with a density range it from .45 to 1.65 is printable, > though that is 'pushing the envelope, and I rarely have negatives that > extreme unless I am doing either very low light work, or sometimes what is > called 'high key' portraiture (little girls in white dresses, sitting in a > white rattan chair with a white backgound, holding a white teddy bear or > kitten!!). > > Once you have 'calibrated' you can then get very controlling as to what, and > how you print. Once you sttle on a good paper/developer combination, you > will be an unbeatable printer, and find that you waste a lot less time and > material getting what you want!! > > Just my .02 worth! > Good luck, and best of multicolored light to you! > Dan