February 20, 2007

Fixing hairline strokes with the Magic Wand

My friend Myke Ninness likes to refer to the Magic Wand tool in Photoshop as the Tragic Wand. And it's certainly no coincidence that Photoshop CS3 features a FANTASTIC "Quick Selection tool" that now finally makes the Magic Wand tool that much more irrelevent.

However, the Magic Wand tool in Illustrator often goes unnoticed, even though it can be quite useful. For example, it can be used to fix hairline rules.

As you may know, computer programs like InDesign, QuarkXPress, and of course, Illustrator, allow you to specify a custom width, or weight, for a stroke attribute. But computers can specify any width. And designers who may want really skinny rules or lines may specify stroke weights in the order of .1 points. While it will show up on a printer, and even on a laser proof or film separations, nary a printing press in the real world would be able to hold that kind of rule. The result would most likely be that the rule wouldn't appear on a press sheet at all. The ink droplets would simply be too small to stick to the surface of the paper.

Therefore, designers, production artists, and prepress operators will never specify a stroke weight below a certain value (for me it was always .25 pt, but for others it might be .3 pt or even .5 pt). The exact value would also depend on the type of printing and the type of paper used. In any case, problems arise when you edit files because objects are constantly scaled and resized, and if Illustrator is set to scale strokes, then it's possible that some strokes will be set lower than a value you're comfortable with.

You can't use the Select > Same settings because you may have hundreds of strokes that were each scaled separately, meaning you could have hundreds of different stroke weights that could be problematic. A manual solution is to select each stroke, check its weight, and move to the next stroke. But some of us like to spend less time in the office and more time with the family. There are also some wonderful plugins that can help here, but why pay for something when you have it for free?

Double click on the Magic Wand tool in the Toolbar to open the Magic Wand palette. Expand it so that you can see all of the settings and uncheck all options except for Stroke Weight. For the tolerance, specify* your optimal stroke weight (I use .25 pt). Then, draw a new line and give it a .25 pt stroke weight. Click on the new path with the Magic Wand tool.

The result? All objects with stroke weights between 0 and .5 will become selected. You are then free to set the stroke weight for all of the selected objects to .25 pt at one time.

*I've noticed what appears to be a bug. Even if your preferences are set to use Points for Stroke Weight, the Magic Wand palette may still ask for that value in inches. To fix the problem, you'll need to also set your General measurement to Points (you can set it back after you've made the adjustment in the Magic Wand palette).


khiltd said...

I wouldn't swear to it, but I believe my favorite stochastic press operator can pull those hairlines off on coated stock.

Mordy Golding said...

Yeah, but not if the strokes are knocked out of a four-color background ;)

khiltd said...

No, I don't think I'd try to reverse one out of anything other than a spot color, but IF a tiny amount of halation were acceptable I think they might be able to stair-step a pullback that would let it breathe enough. Depending on the color(s) in question, this might yield acceptable results for folks who really, really (think they) need them and have the money to waste on experimentation. Another alternative would be to add an extra plate for white ink and do some fancy white overprintin'.

I can't personally imagine a practical use other than for security pseudo-watermarks and the like, but it's a great big crazy world out there.

Teri Pettit said...

Actually, quite a few vinyl cutters and die cutters use hairline strokes to mark paths that should be sent to the cutter instead of printed.

I think Illustrator should do like most other drawing programs, and have an explicit "Hairline" setting on the Stroke weight popup menu, instead of using zero to indicate hairlines. (Since the Stroke palette treats entering a weight of 0 as a synonym for turning off the stroke altogether, i.e., setting the Stroke color to None, the only ways that I know of to get 0-weight strokes with a stroke color other than None into an Illustrator file are to either import them - including opening an Illustrator file older than version 7 - or use the Outline button in the Pathfinder palette. But once they get in the file, they act like proper Postscript hairlines.)

jgts said...

Hi Mordy,
I don't understand the logic behind this... If you had your Magic Wand setting at 0.25 and drew a line at 0.25, why did it select everything under 0.5?
I would've thought it would have selected everything under 0.25.

jgts said...

Ooops, never mind about my last post, above. I now understand that by typing in 0.25 as a tolerance, it's selecting anything 0.25 thicker or thinner than the selected stroke. Makes sense to me now.

Nathan said...

Thank you, thank you, thank you.