Wednesday, 17 December 2014

Tiny Colo(u)red Dots

Sean Michael Robinson:

Greetings everyone!

The past two weeks I've put in some serious time trying to tie up all of our loose ends, including the laborious process of going through the whole of High Society, one last time, to re-check the exposure of each page in preparation for the printing in January. But most of my work this week was finishing up Cerebus Archive Number Two, getting the layout pinned down, working out the kinks of the variable data printing that we'll be using to number the plates, and, most fun for me, tweaking the images for the best possible appearance in print.

If you're reading this, and you have any interest in color reproduction at all, I would whole-heartedly recommend you purchase the book Real World Image Sharpening by the late, brilliant, Bruce Fraser. It's the best possible tech book, concentrating on the theory and real-world application of those theories, rather than just procedures. That focus is why the book can be five years out of date and still be the best guide available for anything related to sharpening. The tools may change, but the whys and the wheres remain the same.

So, what exactly is sharpening?

The original "soft" scan. This represents less than an inch across of the final print.

For a wide range of reasons, and to varying degrees, all digital imaging techniques invariably soften an image. This is true whether you're working with a digital camera, or a flatbed scanner, or even a high-end drum scanner. Additionally, all methods of full-color reproduction do the same thing. Picture, if you will, the millions of tiny colored dots that make up the average full-color print. Through a miraculous flaw in your vision, the result appears as a continuous tonal image. But the result of all those dots is a diffusion of detail, a "softness" that's difficult to avoid.

So, you improve your output device, you improve your substrate, i.e. your paper. Coated paper holds ink with less expansion, therefore, your dots can be smaller, carrying more detail from source to print. Additionally, you compensate for what expansion there is with correction curves that try to predict dot gain and adjust accordingly. But still, the image gets softer. 

That's where sharpening comes in.

Sharpening is essentially contrast-boosting edges, controlled by threshold (i.e. what is considered an edge), amount (strength), and radius. The radius is what gives you real control. How large of an area should this effect cover? Smaller radii bring out high-frequency detail, and larger radii are for softer-focus targets.

The CANT plates are being printed on coated stock, using special high-resolution output devices. The result is lots of room for high-frequency detail, as long as the supplied files are sharp enough. The goal is you feel like you're holding the original art in your hands, and the original target is a flat object, so the more detail the better. (This wouldn't be the case with, say, a photographic portrait, where sharpening brings out unwanted and unnatural levels of detail in undesired areas, such as skin tone)

With that goal in mind, I did extensive proofing on this round of plates, driving back and forth from my studio to the local printer that has a fancy-pants Xerox setup very close to the one that CANT will actually be printed on, each time bringing sharper and sharper files with me, each time being pleased with the incrementally better result. The major takeaway from this is that the real-world, in-print effect of sharpening is fairly minor compared to the on-screen, in-file results, which look dramatically different.

The same area of the print after a minor contrast adjustment and then sharpening. Notice that, at this level of zoom, the sharpening seems too much, too exaggerated, too "crispy." I'm compensating for the loss of detail that will occur during the printing.

Finally. here's a closeup of the same area of the final print. You'll notice that what seemed to be "too much" in-file has softened into "just enough." There's no real gain of information, only full retention of all of the information that was present in the original scan.

Once again, this is difficult to demonstrate on screen, but very easy to see in print. When you all receive your CANT prints in the mail, I hope this will give you some insight into the process that brought them to you.

For a good overview of sharpening, much of which is lifted straight from Bruce's book, check out this summary here.


Michael Grabowski said...

So will there be an announcement when it's time to place an order with my LCS for the new 30th Ann Gold Edition of HS? I don't pay attention to Previews and don't want to miss it like I did last time.

Sean R said...

Hey Michael,

Yes, we'll try to have multiple announcements up. I'm sure Dave will correct me if I'm wrong, but it should be listed in the January previews. There's an ad for the book running then as well. Which would make the release date sometime in March, I believe.

Michael Grabowski said...

Good to hear. Thanks, Sean!