Center spread from a fund raising brochure I produced in 1992 for St. Mary of the Plains hospital in Lubbock, Texas. The duotone printing, done at a firm in western Massachusetts, was executed the old fashioned way—with process camera negatives made from my silver prints by an elderly craftsman who spoke with a Scots accent. He looked at the prints, very carefully, and slowly, having decided how he wanted to interpret my work for the press, said, “You’ll nae be wantin' any black printer in the shadow tones, then?”
Written by Carl Weese
In my recent book review post, I touched on the topic of different offset litho reproduction processes. The most common today is CMYK, which produces “full color” printing. Monochrome photographs can be printed in CMYK, but it’s not ideal. Multiple plate offset printing with black and gray “spot color” inks is a better way to get really good monochrome photographic reproductions that are also smoothly consistent form after form, and so page after page in the publication.
An offset press halftone plate when printed can only distinguish 50–70 levels of tone. (The wide variation depends on the type of paper, the press, the care taken, etc.) Even 70 levels severely limits print quality. Almost as soon as offset lithography was developed, people figured out that they could make a vastly better monochrome print (neutral, warm, cool, livid green, bright magenta, anything you want) by using multiple plates with different inks. Two, three, four—as many as you can afford. Separation negatives were shot so that in a tritone, for example, one recorded primarily highlight values, another mid-tones, another the dark values. Using one black and two gray inks, (counterintuitively, the black ink is best used for the highlight printer, as I learned from the Scotsman) the result, this not being an ideal world, isn’t 210 levels of tone, but it’s a whole lot more than 70. A really well executed page can rival the original silver print.
Process cameras are about as common as dodos today. So, Adobe Photoshop has a duotone function, which includes the ability to make tri and quad tones, from digital files that have been captured, or scanned from film or prints. You can specify any Pantone ink formula for each separation, and you can adjust the curve for each. These controls are the digital equivalent of what a skilled tradesman used to do with the process camera. The file (incorporated into the page layout document) is then output as two, three, or four ultra-high resolution imagesetter negatives at the print firm, then plates for the press are burned from the separations. The plates are mounted on a multi-station press with the specified inks in the correct fountains, or the plates and inks can be used in sequence for multiple runs through a single station press in registration. If all goes well, the result is a publication with beautiful reproduction.
There’s a completely different way to use the duotone dialog. You can use it essentially as a Photoshop filter, best done in a duplicate layer, to manipulate the tint and tone of a file that you will send to a photo quality inkjet printer. The result, however, just to get picky about it, isn’t a duotone—it’s not made with differently inked multiple plates on a printing press. It’s a composite RGB print. Photoshop and the print driver interpret the file data into RGB, because that’s the only language the inkjet printer can understand.
Recently I’ve been studying and experimenting with the Photoshop duotone function because I plan to use it for the plates in an upcoming book project, and I plan to do the tritones myself. It’s a powerful dialog and can create interesting monochrome effects. However, despite the time I’ve spent learning to work with it, I don’t plan to use it on files destined for my inkjet printers. I can get the results I want easier-faster-better with Epson’s Advanced Black & White print driver module for my 3880, or with Photoshop color management and custom ICC profiles for my HP Z3200.
If you try the Photoshop duotone tool and there’s something you love about the interface and you find it helps you reach the results you want, then by all means go ahead and use it for files intended for inkjet printing. These choices are all subjective. Me, I’m only planning to use it on work destined for a Heidelberg.
©2015 by Carl Weese, all rights reserved
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