November 2007

Monthly Archive

Curving Cyanotype

Posted by on 26 Nov 2007 | Tagged as: Digital Negatives

I made a few cyanotype test prints to define a correction curve to be used with image files. The curve was created with the Hinkel & Reeder method, printing grayscale negatives using all inks of an Epson R1800.

The ink density produced by the printer seems to be high enough for the traditional cyanotype, which I was using. But it would not be adequate if I were to try it with the new cyanotype or, say, salt print.

There are, however, methods to increase ink densities – one of them is to use QuadTone RIP which will allow you to bypass the Epson printer driver limitations and create custom profiles which control the printerÂ’s ink settings. More on this on the Digital Negatives website.

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Two samples of test prints from Epson R1800 grayscale negatives. After creating the correction curves they turned out to be nearly identical for Somerset (left) and Canson papers.

I will do some testing with the new cyanotype too – there is yet another method for colorized negatives to be tried. More on that later.

Tests in Blue

Posted by on 15 Nov 2007 | Tagged as: Cyanotype

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Testing cyanotype papers by exposing with UV-light.

We took eleven different watercolor and etching papers that we were able to find in our school’s paper stock, and made a few exposure tests using the traditional cyanotype process (blueprint), with a view to finding a standard exposure to produce the maximum “black” for each paper. At the same time we examined the suitability of these papers for printing cyanotype, and compared the blue tones the papers could produce.

The classic cyanotype is known to work almost on any paper, and mixing of the sensitizer is simple enough: you only need two chemicals to make two separate stock solutions. This time we didn’t mix them by ourselves but used ready-made solutions by Hopeavedos, a Finnish supplier. We coated the papers with a mixture of the two solutions (see the formula at alternativephotography.com). None of the papers were given extra sizing.

As we expected, there were no great differences in tone or sensitivity between the sensitized papers. The exposure times to produce maximum tone density varied from 6 to 10 minutes when exposed with our UV-exposure unit from one meter distance. All samples were exposed in a vacuum frame, partly covering the sensitized areas with blank Agfa CopyJet transparency, hoping to find out something about its UV-transmittance properties.

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Below are the results of our little paper survey – we scanned pieces of each paper showing maximum cyano density plus the uncoated paper base (samples shown approximately life-size). In conclusion, our experience is that all of these tested papers could be used successfully in the traditional cyanotype printing. However, there are a few papers that print better than the others.

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Arches Aquarelle 300g

Very good paper for cyanotype. Can produce intensive blue. Nice surface texture.

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Canson Montval 300g

Both tested Canson papers are our long-time favourites. Prints and clears well.

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Canson Tradition 300g

More textured than Montval. Slightly deeper blue, towards ultramarine. Also the smoother back side works well.

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Fabriano Accademia 200g

Very hard, white and smooth paper. Works well when not over saturated with sensitizer.

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Fabriano Bianco 285g

Velvety surface, a little difficult to print. Touching wet prints tends to leave marks.

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Guarro Casas 250g

Very white base, prints deep rich blue, clears well.

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Guarro Casas Cream 250g

Both Guarros are excellent cyanotype papers, this one has warmer cream hue.

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Hahnemuhle 300g

Etching paper, maybe a little too soft for cyano, but it works. You can easily abrade the wet surface though.

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Somerset 200g

Our first favourite from this set. Although not one with highest max densities, it is easy to coat, predictable and attractively textured.

Colorized Negatives

Posted by on 03 Nov 2007 | Tagged as: Digital Negatives

It looks like printing grayscale negatives using an inkjet printer’s all inks works well, when the tone range of the intended photographic printing process is quite short, so that we need relatively low contrast negative. We aim for a negative with enough density to print “paper white” with standard exposure (the shortest exposure to produce Dmax, the maximum black) for the printing process in use. Not all inkjet printers can lay down enough density to produce decent negatives for some long tonal range processes (salted paper, new cyanotype, palladium…). In that case it may be possible to make colorized negatives, trying to find an ink color which acts as a color filter, blocking UV-light more than gray-tone negatives can do. With printing the negative with this particular color we can use its UV blocking density to produce paper white in our photographic printing process. For more on the subject see the sidebar link RNP Array.

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This image (The HSL Array) can be downloaded from the RNP Array website and printed with an inkjet printer on transparency. We have used this image for determining our “blocking colors”, according to the instructions by Michael Koch-Schulte at the RNP Array site.

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This print from the HSL Array output, made with an Epson R1800, then contact printed on Kodak Polycontrast paper, is one of our first exercises with colorized negatives. We have chosen R0-G12-B51 for the optimum blocking color here.

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Another print on the same paper, printed with the same settings as the one above. The inkjet transparency was made with an Epson Pro3800. This time R242-G20-B0 was chosen for the blocking color, because it makes a nice and smooth grayscale (and we wanted to try something that is far from neutral gray).

We can notice that two given printers can build somewhat different shades of colors from the same image file, when used without any color management. Anyway, choosing any of the acceptable blocking colors should do the job equally well.

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These are our colorized step wedge files, ready to be printed on transparency. Two different printers – two different colors: The R1800 (left) and the Pro3800 (right). Although their colors are very different, they should print about the same grayscale gradation on b&w photographic paper.

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The contact print from the colorized negatives with the standard exposure. We chose to continue experimenting with the 3800 negative (right), because of slightly better highlight tone separation (and because we wanted to see how the red negative will manage the process).

The print highlights look quite good, but the shadows are dark and blocked. We need a correction curve in Photoshop to fix this. Measuring the test print’s density values and calculating the shape of the correction curve by hand can be laborious, but fortunately there is a computer software to do all this: ChartThrob by Kevin Bjorke is a javascript for Photoshop, it can automatically both create a step wedge to print on transparency and evaluate the print made from the transparency, and even build the correction curve needed.

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The next print with the curve applied. Looks much better now, here we are getting basically a nice full tone range.

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Only printing “real world” photographs will finally tell us about the usability of the chosen blocking color and correction curve for the chosen photographic printing process. This is how a red, corrected Epson 3800 negative looks.

Test Prints
A few test prints on Kodak Polycontrast II RC, made with the Epson 3800 red negatives and correction curves built by ChartThrob (you can click pictures larger):

Our first print with colorized negatives. Looks ok, except for some posterization in the deepest shadows (which is evident in the negative too), and when compared to the image on the computer screen, we wanted the lower midtones slightly darker. So, after this print the curve was tweaked a little.

Again the print is acceptable but not perfect. A little more shadow darkening was made to the curve after this print.

We’re satisfied, the colorizing / curve correction tool is working for us! This print is very close to what we see on the computer monitor.

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The starting curve (left) calculated by ChartThrob, and the adjusted curve after test printing.