Wednesday, 7 January 2015

Blurring the Night Away

Sean Michael Robinson:

Greetings everyone!

I'm going to try to keep this update very brief, mainly because I've written... how many posts since this weekend?

Anyway, on Saturday I posted a fax from Dave requesting I expand his white-on-black lettering on a few pages of High Society. He suggested a few ways I might do that, most of which (creating another font, "drawing" the letters thicker, cloning individual letters) would take a lot of time to execute.

Fortunately I didn't need to use those techniques, except very selectively. Those of you interested in the how, read on.

First off, you might wonder why white on black lettering is so fraught with peril. Cast your mind back a few weeks to the discussion of print technologies and ink expansion on paper. Dot gain is the generic term for the tendency of ink to expand once it hits the surface of a substrate. The type of substrate dictates the degree of that expansion-- the more coating on a paper, the less expansion. Uncoated standard web-offset paper like we're using for this edition of High Society has significantly more than that-- newsprint even more.

So when you have a white stroke on a field of black, what you really have is a sliver of unexposed paper that has ink encroaching/expanding into it from all sides. So a black stroke on white of a certain point size can easily readable after printing, but a white stroke of the very same size could end up filled in and illegible.

Anyway, here's how you can expand a linear element in Photoshop.

Here's a screenshot of my Photoshop workspace, with the page in question open. You can see that the lettering wasn't actually created in white ink, which is a tremendous pain, let me tell you-- rather, Dave created the block of lettering in black on white and had Preney Litho make a PMT (photomechanical transfer) of the work in reverse, which was then pasted up on the page. Same with the header. Unlike some of the PMTs, this one has held up really well.

For the curious, a closeup of Dave's instruction to the printer. 

You'll notice in my layers menu that I have a Threshold layer at the top of the stack. This enables me to "turn on" the threshold easily at any given point during the work to check how the result will look when I'm actually ready to output the page.

Here's a closeup of an area of the text. You can see developer (?) streaks and a bit of "grit" in the PMT that would come out if I adjusted these areas too aggressively.

Now here's a screenshot of the text after my normal sharpening routine has been applied. (In this case, there were about forty pages that seemed to have been scanned by the same scanner with the same settings, so it really was a "routine"-- I made an automated script for those pages, and ran it each time I encountered that source.)

You'll notice that the linear streak down the center of this segment is probably dark enough to disappear when the threshold layer is applied. So, in lieu of any further instruction, this page is ready for any cleanup.

What's that Dave? You need the white text larger?

Here's how we'll accomplish that goal.

Here's an extreme closeup of what we've got. Notice that our edges of the letter forms are now very sharp-- little ambiguous gray edge pixels at all, exactly what we want in order to retain as much information as possible in print. But since we want to expand these forms, we're going to need to fix that with a little gaussian blur.

In Photoshop, you'll do this under Filter-> Blur-> Gaussian blur. The radius of the blur depends on A. how much you want to expand the object and B. how much edge information you can afford to lose. Gaussian blur is almost miraculous when dealing with curves, but it takes some of the refinement and detail out of corners. For this purpose, though, it's perfect.

Now I'll turn on the Threshold layer so we can get a preview of the final result, and the open the Levels dialogue. I'm going to move the White Point lever downward until we have the letter form the size necessary. (The reality is, I'll usually do something like this incrementally, making soft proofs (i.e. laser printer printouts) as I go to check how things are proceeding.)

As you can see from the image below, with a blur radius of just 1.8 px, we can expand the letter forms to more than double their initial stroke. (Not that we need to do that here!) If we needed even MORE expansion, I'd have to apply a wider radius of gaussian blur in order to accomplish that.

Well, that didn't exactly turn out to be a short one, did it?

Hope you enjoyed this peek into the process.


As requested, this is a screenshot of the final enlarged text. Though size is hard to judge on screen in Photoshop with line art-- something to do with the way they scale in the program. (This is also why people drive themselves crazy "cleaning" tiny flecks of white on black that will never make it to the page-- Photoshop exaggerates their prominence in the scaling)


Sandeep Atwal said...'s like Deja Vu all over again!

Sean R said...

Hey Sandeep!

I think Dave is probably having a pretty severe bout of deja vu himself!

By the way, anytime you're ready to spill the beans on the remainder of your tricks, I'm all ears :)

Jason Penney said...

I love these posts. Can you post a zoomed out "after" image (like the third and forth ones)?

Steve said...

I ran sheet-fed presses(as opposed to web press) for close to 18 years. Trying to print an image with white lettering when the surrounding image is four-color (this on a two color press) is quite a challenge.

Just as Sean says, uncoated stock and the ink dots spread - but now, you've got four colors spreading on you in addition to paper swelling / shrinking between passes, registration error from paper feed problems...

You know, I now get to deal with (the occasional) cranky ophthalmic surgeon; I really don't miss those presses much!


Sean R said...

Hey Jason--


Sandeep Atwal said...

Hey Sean, email me anytime: