Wednesday, 31 January 2018

Paper To Pixel to Paper Again, Addendum B: Working in Color, Part One

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A guide to creating the best looking line art in print in the new digital print world

Addendum B:
Working in Color, Part 1

This is the second addendum to Paper to Pixel to Paper Again, a series that explains (in an overly thorough manner) the how-to's of preparing line art for print.

And as always, if you have any questions, please let me know in the comments!


Oh, hey, another addendum!

Oh, hey, a really really long addendum!

While writing this series, several times I've had requests for information about working in color. And while the majority of the Cerebus restoration work has been working solely with line art, over the past few years I've learned the ropes of color reproduction and have plenty to say on the subject.

However, it's a complicated topic and a really thorough look at it would take more space and time than I have here. What I'm going to do instead is give some general principles that will hopefully help you get your work to reproduce a little better.

This post ended up being so long, I've split it into four parts, which will run over the next four weeks. So keep any eye out for the next one next Wednesday!

Signal Path for Graphics

For about a year and a half, more than a fifteen years ago now, I attended a small Central Florida community college, taking courses in audio engineering. It was there that I first encountered the principle of signal path. That is, when you're attempting to understand a system for the first time, one of your first tasks should be to understand the path—the routing through which your signal will (or can) travel to before it reaches its destination.

In the case of working for print in color, with a traditional color offset printer, the signal path is fairly straightforward—

Input Device (e.g. scanner, camera, or even tablet, if you're working digitally)
Graphics Software/touchup (Photoshop, Gimp, MS Paint, etc)
Layout Software (Indesign, Quark, etc)
Printer's Layout and Imposition Software 
Printer's Raster Image Processor

Each of those steps has their own quirks and pitfalls and opportunities to degrade your image, but, just like in the audio world, for the end product to be stellar, the front of the chain has to be right. 

How Does Your Color Work Get in This Here Little Box? I.e. Picking an Input Device

If you're working with relatively durable (and flat!) transparent media, then a really good flatbed scanner is hard to beat as an input device. 

When is a scanner not necessarily the best choice? One, if your artwork has too much relief, i.e. physical depth. Two, if your artwork features media, such as charcoal or wheat grass or something, that won't stay on the paper if pressed to a glass. Third, if your artwork uses materials that are reliant on reflection for their visual characteristics. Examples: paint/glitter pens, glass, metallic pens, gold leaf, etc. 

As for selecting a scanner: your first stop should be this post by me, from this very series!

Adding to that post—when you're going to be scanning color work, it's even more critical that you spend upwards a bit on the scanner side. Color consistency (different than accuracy, as you'll see below!) comes from better optical elements, better electronics, more critical factory tolerances.

As to what's the best choice: I've still yet to see a flatbed better than the Epson 10000XL or its  identical twin, the Epson 11000XL. (Neither of these is still manufactured, having been superceded by the 12000XL. I can't verify that the 12000XL is identical to the other two, but the older models are still available in great number on the ol' Ebay. If you're feeling brave and can afford to wait, you can probably pick one up for less than $600, which is what I did a few years back! Just make sure you ask the seller to lock the scanner motor before they ship—it's attached to the power cable port.)

The First Steps: Calibrating Your Scanner

[The following is from a post I wrote here in October of 2016. By quoting extensively from myself, I'm hoping to be able to pack a lot more information into this single post!]

I've written here, exhaustively, about scanning, about sharpening, about turning physical artwork into ones and zeros and then back into physical artwork again. But I've written very little about color. So with that in mind, and seeing how many of the people who chime in here are artists themselves, I thought I'd write about color a bit, in the least sexy way possible, as is my way.

TLDR: If you scan color artwork, you should be color calibrating your scanner.
Those of you who have been following along with the restoration work from the very beginning, now more than two years ago, might remember that, after taking some time off for a world busking tour, I'd been working as an illustrator and writer. When I first started talking to Dave about the print problems he was having, I had been living in San Diego less than a year, and most of my income was coming from freelance work I was doing, both locally and remotely. I had a long multi-month job with a startup tech company, making paintings and designs for a graphics-intensive app. Graphics for another training app for a different startup. Posters for shows—mostly music and theater, both in San Diego and for shows in my previous homes of Seattle and Orlando. Memorial portraits. Gift portraits. Odd jobs, truly odd, like producing artwork to be used in films, sometimes even in stages, so that an actor could "draw" my work on camera. 

Anyway, although most of this work was produced for color in mind, the majority of it had an extra layer of digital assembly or color adjustment, using the digital as a way of working quicker despite my reliance on traditional media. After all, if you're producing work primarily for print or screen, it doesn't really matter if your "original" is in fact an assembly of half a dozen different pieces of paper and not one seamless whole.

But the past few months, I've been painting a lot more, and working in a more disciplined fashion, attempting to make the finished product solely on the art board or watercolor block versus relying on layering and adjustment to finish it off. And because of that, I've become a lot more picky about color.

This is a good example of digital assembly. I made the line art drawing and inking on one side of a thin piece of art board, then flipped it over and colored on the reverse using Higgins dyes, painting on my lightboard so I could see the lines through the paper. So this illustration doesn't really exist in the real world, only a strange two-sided original.

The scanner I'm currently working with is the finest flatbed scanner I've ever seen—the oversized Epson 10000XL, optically sharp and, with no lip and a removable lid, specially designed for being able to scan oversized artwork. It's the same scanner that both Sandeep and Gerhard are using for scanning Cerebus originals, and it's giving us great results for line art.

But as my painting's progressed I've been getting more irritated by the amount of time it takes to adjust my colors after the scan. And on a complex painting with lots of transparent overlays, it seemed like I would never quite get there.

So what's to be done about it?

Fortunately, there's a very easy solution—color profiling and calibration.

Imagine, if you will, the difference between accuracy and consistency. In this case, my scanner has relatively consistent scanning of color, at least over a period of a few months. It's just consistently off.  Light reds and mid-tone yellows always seemed way too intense, blues subdued and muted, But because it's consistently off, if there was a way to recalibrate it...

No surprise, such a thing exists. Equally no surprise, it was developed for the needs of photographers, who happen to outnumber cartoonists by, oh, quite a bit. 

What we're looking for is called an IT8 target. You scan this target in your professional scanning software (i,e, either Vuescan or Silverfast) and reference the file supplied with the target, and voila! all color adjustment woes are gone, at least for a few months. (The standard recommendation seems to be to re-calibrate every few months, unless you're doing extremely critical color work or are working on an ailing scanner. Fortunately, using the same target is just fine, as long as you haven't been storing it in the sun!) 

Being the frugal person that I am, I purchased my IT 8.7 target from German color obsessive Wolf Faust, who manufactures them himself and ships him out of his home in Germany. All told I paid $20 for a single target, less than 10 percent what I would have spent purchasing one from another source. The package arrived a few days later. Fifteen minutes of following instructions later, and I was done!

It's an amazingly simple concept. The package contains the target, a specially-prepared print on photo paper, representing a full range of values and tones. It also includes a data file that acts as calibration, listing the expected values. Once the calibration scan has been made, Vuescan (or Silverfast) can reference the supplied file and make adjustments to the actual results to correct for the result that had been anticipated. In other words, changing consistency to accuracy.

This is the illustration that finally motivated me to get the color calibration sorted out. I started the whole painting with various intensities of yellow, resulting in "hot" foliage and "cool" foliage for the different types of plants. The over-intensity in yellow of the original scans were making the hot foliage appear to be way too hot, sunburnt, while the cool foliage looked sickly, nothing at all like the original artwork. The above is a raw scan with only a levels adjustment. 

The new norm has been — power on the scanner, open up Vuescan, make sure my settings are still loaded, and scan that sucker. 90 percent of the time the raw scan now only needs a levels adjustment to make me happy.

This too can be yours, for $20 US and a little bit of patience!

Step One-

Step Two-

Step Three-

Step Four-
Make sure you are consistent your color spaces! Vuescan and Photoshop should be operating in the exact same color space for best results. I'd recommend AdobeRGB. 

But What Resolution Should I Scan My Color Artwork At?

That depends on your destination print size, and the size of your original artwork, and the fineness (or coarseness) of the color half-toning that the printer will use. The smoother the paper, the finer the half-tone screening can be, and thus the more fine detail can carry through the screen. (More on this below...)

The "received wisdom" on this topic is that there's no benefit to higher resolutions, but I can tell you from long experience and many hours arguing with printers that, depending on the source material, printed on coated paper with the tightest screens, there can be a difference, visible to the naked eye, between color printing supplied at 300 or 400 ppi and 600 ppi. 

The principles from the first few articles of this series still apply. The higher contrast and more finely-detailed the image is, the more important it is to supply a high-res color file. The lower res your image, the clunkier the edges can be on your resulting image.

So—eventual destination has a lot to do with how much difference that extra res will make. But the safest thing to do is scan at a res that will enable you to deliver your at-size file at a max of 600 ppi. For most images, however, and to most eyes, there will be very little difference between images printed from 400 ppi and 600 ppi files.

A photograph of some clouds in a blue sky? Unlikely to be any difference. A very sharp color reproduction of someone's line art drawing, i.e. lots of tiny high-contrast lines? Here's where the extra resolution can really matter.

(That being said, whenever artwork I've painted or drawn will be leaving my hands, I make an at-size 600 ppi scan, to add to my digital archive. Hard drive space is cheap, and you never know when you might be able to use the scan).

Okay. What Now?

So, working down our "signal path" chain...

We're now "in the box", our scanner color-calibrated, our artwork safely scanned and on-hand, ready for any manipulation we'd like.

But being "in the box" presents us with a new set of challenges, mainly, making sure that our monitors are giving us accurate color information while we work.

Next: Real-World Examples!

1 comment:

Anonymous said...

Thanks for the in-depth article! As for scanning resolution, I'm curious what a comics artist, like Neal Adams has his pages scanned at. Somewhere or other I heard Marvel/DC scan at 1200 dpi. I just found another post from this comic blog where it's suggested to scan at 800-2000 dpi for what seems like an 11 by 17 image area. Just as an aside, the couple average scanners I've tried this with can't even complete the command at 1200 dpi, of course I know of the Epson 10000, though that is cost prohibitive at the moment.