Wednesday, 7 February 2018

Paper to Pixel To Paper Again Addendum C: Working in Color, Part 2

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

Addendum C:
Working in Color, Part 2

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!


Monitor Calibration?

The best way to ensure that "what you see is what you get" boils down to two things—the quality of your monitor, and/or the calibration of that monitor.

Just as you used a target, with known measurable values, to profile your scanner, you can do the same for your monitor, using a wide variety of devices.

That being said, the more dough you're expending on a monitor, and the newer the technology, the more stable the color representation is, and the less helpful calibration is. How radically has the market changed in the last few years? The 4k monitor I use, the DellP2715Q, sits at a definite "prosumer" price range, but has unbelievable color reproduction and so-called "factory calibration". While monitor enthusiasts (otherwise known as tech-obsessed photographers) will still find many nits to pick, for my purposes, this monitor has been more than adequate without any additional calibration.

Oooh Oooh, is it Example Time??!

Above is a raw scan of a commissioned portrait I painted this holiday season. I scanned it in Vuescan, using my color-calibrated Epson 10000XL, but not paying any particular notice to the exposure, other than making sure I wasn't clipping (blowing out) the paper color or the dark areas.

Let's say (for the sake of this demonstration) that we'll be reproducing it at half the size of the original. Then I could safely scan it at 300 ppi RGB, knowing that I can change the size of it in Photoshop to half the size at 600 ppi without any actual scaling at all.

After the scan is complete I open it up in Photoshop and carefully compare the scan to the original. The first thing I notice is the muddiness of the scan. We need to adjust the exposure.

The paper I painted on is a little creamy, not blinding white, so I'm not going to knock out all of the color. I go to Layers -> New Adjustment Layer -> Levels to bring up a simple levels command.

The exposure problem is actually visible in the histogram. Do you see that empty spectrum to the right of the big peak? That's our unused dynamic range. There's literally nothing in that range of the color spectrum of the document. The big peak, however, is the paper color.

The right slider (the one that looks like a white upward arrow) is your White Point Control. Drag it to the left until the unpainted paper is starting to look the right hue. Then grab the Gamma Control (the center arrow that's gray) and gently move it around until the rest of the color balance is looking good.
Post Levels adjustment. Click to embiggen.

Above you'll see the result. However, upon closer examination, it seems I've got another problem. The raking light of the scanner has emphasized the rough watercolor paper texture in an unflattering way. 

Fortunately there's a way to fix that. 

I take my painting, and rotate it 180 degrees on the scan bed, so it's oriented the reverse of how it was previously. Now I'll scan a second time. 

Because of the rotation, the raking scanner light is now travelling a different path on the document, causing an entirely different set of shadows to be emphasized. We can use this to our advantage to eliminate both.

Copy the second scan and paste it into the original as a new layer. Then rotate it 180 degrees so the two layers are oriented the same direction. Then select both layers, and go to Edit -> Auto-Align Layers. This invaluable Photoshop function is capable of analyzing visual content and aligning based on that content. 

After PS has done its thing, take a minute to do a bit of manual adjustment of your own, using the Move tool (V) and the arrows to drive the upper layer around, periodically turning it on and off to check its alignment. Once you've got it in place, it's time for the Spooky Magic.

Select the top layer and change the Opacity to around 50 percent.

Magically, all of the paper texture will vanish, leaving only the things that the two scans have in common—the actual content.

The look can be so uncanny that sometimes it can be better to moderate it a bit, and back off the setting from 50 percent, which will gradually reinstate the paper texture.

The final scan! Click to embiggen.

Next: Sharpening! (You knew it was coming...)


Carson Grubaugh said...

Where is the "Color Blind Correction" button?

Sean R said...


Weeellll, if color blindless were an issue of degree instead of a complex issue related to the lack of development or processing problems with certain color cones, then you could probably make some kind of compensatory device that, like, ratcheted up the intensity on certain color bands on your displays... but for classic color blindness, I'm afraid not :)

"... ENHANCE!"