Straightening & Scripting
This is the fourth installment of Paper to Pixel to Paper Again, a series that explains (in an overly thorough manner) the how-to's of preparing artwork of all stripes for print.
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If you haven't done so yet, please go back and read the previous installments.
In our last installment, we scanned your masterpiece (1200 pixels per inch [ppi] for your at-size sources of art, 600 ppi for your very large original artwork that will be reduced for print). Then we discussed some general principles of file organization, and how not to get lost in a digital maze of files.
Today we'll use Photoshop to take your raw scan, and generate an "Action" that can do the first stages of page work for your entire book.
I've said it before, but computers do a few things much better than human beings. One of those virtues—carrying out complex commands unerringly, for an unlimited amount of repetitions. If there is a task you will need to do more than once, you should consider making an "Action" or script for it, and saving it to run the next time the issue arises. Something that saves you even a minute per page ends up saving you ten hours (!) over the course of a 600 page book. So use your time wisely.
A paragraph on Adobe Creative Cloud—Adobe is a great software manufacturer who makes an invaluable suite of graphics products, all of which are available simultaneously under a reasonably affordable subscription plan. They also strike a good balance between continually updating their products, and not pulling the rug out from under us oldsters who are used to something functioning in a certain way. I'm going to use Adobe products, namely Lightroom and Photoshop and Indesign, for these demonstrations, because it's what I know; but the basic principles could be carried out with any well-designed graphics program. These just happen to be the best I know.
One Last Prep Before We Go
Okay, remember what I said about saving time through automation?
Let's add an extra step before we tackle these scans.
I've opened up the Adobe program Lightroom, a very smartly-designed piece of software that is the virtual-world equivalent of a photographic development room. You can open up a session or folder of photographs (or scanned images) and treat them as a catalogue—change them, individually or as a group, by re-exposing, rotating, sharpening, adjusting the color, and then A/B comparing the result, or A/B comparing individual images. It's a very deep program, but here we're going to use if for something very shallow. We're going to open up every image in our scans folder for our new book, and rotate them to be perfectly aligned, and then save the whole lot in a new folder.
(But didn't you scan them perfectly aligned? Well, maybe. Maybe if your art board was machine-cut and thus perfectly rectangular, and you drew your panel borders with a t-square perfectly flush with your perfectly-manufactured drawing desk, and then you took this object of 90-degree majesty and placed one edge faultlessly butted up against the raised edge of your scanner. And then did this again on every page.) (So yeah, you might want to rotate a few images, if only a bit.)
Okay. So once you have your catalog open in Lightroom, double-click one of the images to get started.
Since we're not going to be doing very much here, this part is pretty straightforward. Hitting the "R" key brings up the Crop interface. You can now trim the sides, and rotate, and a helpful guide pops up that will help you keep everything aligned. Hit "Enter" when you're satisfied. Because Lightroom is a non-destructive editing program, meaning your original data stays in its own folder intact while you work, you don't have to worry about making a mistake. If you want to change what you've done, just hit "R" again and re-crop, and then hit the right arrow key to move on.
You might be tempted to make other adjustments here, and in another workflow, that might make sense—but for now, just power through and rotate all your images. After you're done, go to File -> Export, and take a look at your options. You want to save them in a new folder nearby your raw scans, with the same file type and bit depth as the originals, with nothing added.
By the way, if you're very fastidious in your scanning, you might be able to skip this step in the future. Very few of the scans I receive from Kitchener from Dave's assistant, for instance, need rotation, as he takes his time getting the alignment great on his end before scanning. Which is hopefully how it is for you as well! I just find this step useful because it allows me to automate an entire stage of my work, and know for sure that I won't have to redo any of it because something needs rotation after the fact. An alternative might be to skip this stage and just make note as you work of what pages need rotation, and attend to them separately. Something I might try on the next book.
CAN WE START NOW??? PLEASE???!!!
Fire up... the PHOTOSHOPS!
I like to imagine it making the old 2400 bps modem handshake sound as it loads... Nahanananah... nahanahanaha... nahanahanaha... beeeeeeeeeeeee!
[Quick caveat before I start this section — Adobe is changing Photoshop, ALL THE TIME. And they break things, all the time. If you rely on Photoshop tools for your work, do yourself a favor and keep all your older Photoshop installations around so that WHEN something critical breaks, you have a way to still continue to use it. I currently have PS 2019, 2020, and 2022 installed on my work computer, for a good reason!]
Okay, now open a few sample pages from your scans. If your artwork has a wide amount of variation to the techniques used, say, some pages composed of only really dense teeny tiny lines, other pages with loads of fine screen tone, some others with spray/airbrush/toothbrush work or some other kind of similar spatter, then make sure each type is represented in your samples. Now start with a page that represents a kind of average for the project. Average complexity, average amount of density (darkness) to the black, something to establish a baseline for the work.
I'll be starting with issue 190 page 18. It's a good representative sample of the book — areas of fine line, two different densities of circular tone, "noise" tone, and some photocopied panels with weak blacks (the backgrounds of the latter two panels are enlargements of the first).
Now we're going to make an action out of the next steps we take, so we can repeat it on other pages. Go to Window -> Actions to bring up the Actions panel. At the bottom of the panel is a button that is called "Create New Action." Click on this, and you'll be prompted to name your action and what set you'd like to save it to.
I've named mine "original test."
Once you hit Record, everything you ask Photoshop to do will be recorded as part of your script. So if you're planning on experimenting a bunch and undoing a bunch of commands, you might need to go back in and clean up your script a bit before being finished, or stop and start it (using the buttons at the bottom of the Actions panel) as you go to ensure "testing" items don't get recorded in your script and slow it down when you run it.
Okay, now that we're recording our Action, the first thing to do is make our color scan grayscale, in the best method possible. Because the original art I'm working with was produced with "non-repro-blue" pencil, this will involve throwing out the blue color channels.
So go to Window -> Channels, if your Channels window isn't already visible.
The "Channels" window next to some visible blue-line pencil.
Now, depending on the brand of the blue line pencil used, and the color cast of the scans, the channel you need to throw out might vary. Click through each of the channels, which will display, in grayscale, the information available solely on that channel. Observe which has the most amount of the pencil visible. In this case, the Red channel is the biggest offender, so I dragged that channel to the little trash icon at the bottom of the panel. Which leaves us with just the Magenta and Yellow channels remaining. Of these, the Yellow channel is the clear winner, so I toss the Magenta channel.
Now that we've selected the very best channel, we're ready to do what we actually set out to do in the first place— make our document grayscale. Go to Image -> Mode -> Grayscale to finish the job.
Now go to your Actions panel and hit the Stop button to stop recording your script. Do you have a bunch of nonsense/unhelpful steps in your script so far? Either try the whole thing again, or delete the unneccesary steps by selecting them (SHIFT- select will select a sequence) and dragging them to the trash icon below.
Here's what mine looks like, after having dumped the less desirable color channels and converted to grayscale—
(You can see there are a few extra moves in there I could delete if I wanted to really clean it up, but none of them will slow down the script)
Now we're going to make one last move before we upscale our art to the actual resolution we'll be working at. I'm going to make a Levels adjustment to knock out a bit of the paper color and see if we can enrich the black a bit prior to the upscale.
If you still have your original art with you, scan your eyes over the page and try to find the finest detail that you can pick out with your eye, whether that be a dinky little line or spatter or a spatter tone. Now zoom in on that area of your scan. Really, really far, like 400 to 700 percent, depending on the resolution and size of your monitor.
Now hit CTRL-ALT-L to bring up the Levels command.
We're going to talk about this window a bit, as we'll be spending an awful lot of time here. (Adobe's official explanation of the Levels histogram, which is a very concise unpacking, is here.)
The above histogram represents the distribution of tonal information within the layer that you're currently modifying. See those two peaks? Those represent the "black" of the ink (on the far left) and the "white" of the paper (far right). And that valley between them represents all of the gray information distributed throughout the image. The lowness of that valley indicates there's not much information there at all, compared to the spikes for the "black" and the "white" of the paper. Which is what we'd expect to see for a grayscale line art scan.
What we're going to do now is move the black point of the image (circled in magenta above) all the way over to the edge of the first peak, effectively making our "black" ink actually black. And then we'll move the white point of the image (circled in lime green above) to the right to meet the edge of the paper peak, essentially knocking out some of the paper color of the image.
[As I mentioned in my interview with Jim Rugg on Cartoonist Kayfabe, in some versions of Photoshop and with some graphics cards, "Levels" commands won't save to your Action correctly. If this is the case for you, you can use the Curves command in almost the identical way I'm identifying here).
While I'm making these adjustments, I'm watching two things carefully. In the areas of black detail (i.e. dense hatching), I'm looking to make sure moving the black point isn't causing any of those details to fill in at all. I want the black point adjustment to only impact the solid black areas and not cause any other effect. Similarly, as I adjust the white point, I'm watching to make sure that the very finest details aren't shrinking at all. All we're trying to do is prepare the page, not get rid of any information. (Yet another reason to be conservative here—we're going to be running this script on every page. So hopefully this is a representative sample of the whole!)
Okay, after you've blackened the blacks and knocked out a bit of the paper color, grab the Mids control (circled in cyan above!) and move it about a bit. This controls the overall exposure (or gamma) of the image. Moving it to the left (towards the black point) will lighten up the page overall. Moving it to the right (towards the white point) will darken up the page overall. Play with this and see if any additional details becomes visible as you move it to the left, or if the blacks become richer without losing any detail as you move it to the right. (Later, when we're dealing with photo negatives, this will be an invaluable technique.) After you've settled on a good home for your Mids you might be able to back off a bit on your other adjustments.
Here's where I ended up on mine.
Now, turn off your Actions recording and let's make sure your adjustment is helping your image.
ALT-CTRL-Z steps backwards/undoes that last thing you did in Photoshop. SHIFT-CTRL-Z re-does that last thing. Skip around in your image, zoomed in, undoing and redoing the last step, and taking a look at the effect. And get used this these shortcuts. We'll be using them a lot.
Now that we're prepared our scan, we're going to upscale our image to our final resolution and size. Hit ALT-CTRL-I to bring up the IMAGE SIZE menu. (Or go to Image-> Image Size. But really, the keyboard shortcuts save you valuable time. Best to take a bit to learn them, especially for things you'll be doing over and over again.)
Here's the Image Size menu. All of the darker gray boxes on the right are breakout options boxes. If you click on the arrow on the right of each, they'll open up additional options.
First, we're going to change our Percent number. Our overall artwork needs to be shrunk to 62.4 percent of its original size, so that's the value I'll enter here. (In the original run of the Cerebus book, the artwork was usually reduced to 60 percent of its original size, but in the remastered books it's slightly larger than that).
Next we'll change the Resolution to our target delivery resolution of 2400 Pixels per Inch. You'll notice that when you change this value, your Percent value changes as well, in this case, multiplying your percent reduction (62.4) times the resolution change (4), leaving us with 249.6 Percent.
Lastly, we're going to change the type of resampling that Photoshop applies to our image. Select Preserve Details from the menu. And then change the "Reduce Noice" slider to zero. (You only need this if you're working with a color image, especially one suffering from JPEG compression or some other kind of artifact that might otherwise get caught up in the upscaling algorithm).
(This is already an overly long entry, so I'm loathe to get too far into the differences between these resampling methods. But I think it's important to note that Preserve Details is fundamentally different from Bicubic Smoother, which is the other method you might use for enlargement. Preserve Details is a fractal method of interpolation that is ALMOST ALWAYS the way to go for upscaling. Exceptions would be upscaling certain kinds of line art with mechanical tone where the mechanical tone has not been adequately captured by the initial scan, in which case Bicubic Smoother is the better way to go)
Here's a screenshot of my final settings.
And now we click OK and wait for a minute...
(Still waiting... now you see why I told you to make all of this an Action! So you don't have to stare at the clock or check the news or check your pointless Facebook feed and find out no one loves you and everyone is clearly happier than you are and hey look there's a video of a man catching a trout with his face, better check out the comments, and it looks like Sylvia's broken up with David again and...)
O hey, it's done!
A Brief Detour—Why Do We Upscale?
As I mentioned back the first and second installment of this series, just because we plan on delivering 2400 ppi 1-bit bitmap images to the printer, doesn't mean we have to scan at that resolution. Grayscale and color scans have much more data per pixel than a 1-bit image, and we can use this data to upscale to our desired resolution, with very little downside at all.
Below you'll find a comparison image I've made with a small portion of the page we're working with. The first image has not been upscaled, only converted to a 1-bit bitmap. The second one has been upscaled exactly as detailed below, and then converted to a 1-bit image, with nothing else done to the image.
As you can see, the upscaling has achieved the goal of bringing us into a much finer resolution space with much smoother edges and details, without affecting the balance of details and dense areas in any way. If you want to make a comparison image yourself, then make a version of your page upscaling with "Nearest Neighbor," then copy and paste the result onto a new layer of your working image.
Back in The Present
Now I'm going to go to the Layers panel and right-click on the layer with our image, and click on "Duplicate Layer." Name this new layer "Sharpened." We're going to make our final adjustments on this copy, so as to maintain the original below.
Next, with our Action still running, click the "Make New Layer" button at the bottom of the Layers panel. Name this new layer "Cleanup." Next, go to Layer -> New Adjustment Layer -> Threshold. This will create a way to preview what our final 1-bit image will look like after we convert it. But for now, turn off this adjustment layer by clicking the Eye icon next to the layer name.
Lastly, click on our "Sharpened" layer and then turn off your Action. We're going to spend a bit of time now playing with different possibilities.
And here's our script and layers panel so far!
So, uh, cliffhanger?? Will we sharpen? Will all of our detail remain? Will the printer forget to clean the press and drive our book to Dotgainville? Find out NEXT WEEK!