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Adobe Illustrator Tip: On Screen Pixelization

Working with document raster settings By Dave Nagel
When you work in Adobe Illustrator, you will occasionally encounter problems where elements appear to be tremendously pixelated on screen--that is, the objects' strokes and/or fills appear to be jagged. This is generally a display problem only, and one that shouldn't trouble you too much, though the problems will sometimes make themselves apparent in your prints as well. There is a simple solution for this. (And if you actually want to create pixelization effects, there's a simple solution for that too.)

Usually when you see pixelization in Illustrator, it means that your document contains raster elements, whether you know it or not. All SVG filters, for example, are raster effects. And, of course, any non-vector-based image you place in Illustrator is also a raster element.

So let's take a look at the problem. Here I have two simple vector-based objects that look fine on screen right now.

Then I apply an SVG filter (Bevel Shadow), and look what happens.

Well, that's just terrible.

The reason is that I currently have the resolution for raster effects set too low, as I'm using the default 72 PPI (screen) resolution. And, at 72 PPI, I'm going to see problems with my prints as well as my screen previews.

But I can easily change this.

Changing raster effects resolution
To manipulate your raster effects settings, choose Effect > Document Raster Effects Settings.

In the dialog that pops up, choose a new resolution for your raster effects. 300 PPI is generally a safe number, although you should consult with your service bureau to determine the ideal resolution for final output.

And here's the result on screen. But it still looks like a problem, doesn't it? (Look at the edges.)

Screen resolution and magnification
The reason for this is that Illustrator, like Photoshop, has a problem displaying raster elements at certain magnifications relative to the resolution of your image.

The examples I've been showing you are displayed at 200 percent magnification. The problem with that is that Illustrator treats screen resolution as 72 PPI. And, owing to the way Illustrator displays raster elements, anything that is not a multiple of 72 PPI is going to look jagged at practically any magnification.

To get around this--if it's important for you to be able to see crisp lines on screen--you simply need to change the Document Raster Effects Settings resolution to some multiple of 72 PPI. For example, 144 PPI or 288 PPI will work great.

To do this, once again open up the Document Raster Effects Settings dialog. This time, instead of choosing one of the preset values, click "Other," and type in 288 PPI.

And now look at our objects!

Looks great, and it will look great at magnifications of 25 percent, 50 percent, 100 percent, 200 percent and 400 percent. (At other magnifications, you will still see jaggies, but this is a display problem only and won't affect the final output.) And at 288 PPI, it's going to be good enough for just about any print job--though, again, you'll want to check with your service bureau to make sure.

Intentional Pixelization
So what if you actually want pixelated edges on certain objects in your document--say, for example, you're trying to create a '70s/'80s videogame effect? Well, in that case, you can simply decrease the resolution of your objects either through the Document Raster Effects Settings Dialog or through the dialog that pops up when you rasterize objects. (The latter is generally the better option, as it doesn't require you to apply effects to your objects and doesn't affect all objects in your document, just the ones you want pixelated.)

Here's how it works.

First, I'll clear the effects off my objects so that they're once again just plain vector shapes. Then I'll select them and choose Object > Rasterize.

In the dialog that pops up, I'll click "Other" and type 16 PPI.

And here's the result.

You can choose other raster resolutions to increase or decrease the pixelization effect.

If you have more questions, be sure to drop me a line in the Adobe Illustrator forum at DMN Forums by clicking here.

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Related Keywords:illustrator, adobe, raster, pixelization, pixelation, jagged edges, screen, resolution, raster effects settings

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