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The Difference Between Raster and Vector Images

Posted by on in Artwork and Design

Have you ever spent any time with a group of graphic designers, computer programmers, or a group from a similarly geeky profession that you don’t share? Set your stop watch, and see how long it takes before they start dropping jargon and lingo that sounds like a foreign language. If you can’t decipher what they’re talking about, you probably tune it out in a hurry.

Sometimes, they’re talking about the technical aspects of things we take for granted, but as laypeople, have no capacity for appreciating. If you take the time to understand what they’re talking about, you may develop a new appreciation for everyday phenomena.

For instance, most folks don’t give images a second thought, as long as they get the job done. How complicated can they really be? As it turns out, images are quite complex. Stay seated for a discussion of the difference between vector and raster graphics, and you might look at images in a different way.

Raster than a Speeding Bullet

A raster graphic is composed of pixels, or tiny dots. Viewed from a distance, the collection of pixels looks like a solid image. Get closer (a lot closer) and you see that image for what it is: a bunch of dots. A perfect example is the color pictures in newspapers. They are printed in four colors as raster images, but the ink migration and the sheer concentration of pixels blurs them into a solid picture.

In fact, raster images are perfect for photographs, since they excel in creating fine gradations of color and texture. The popular photo editing software Photoshop is a raster image program.

What’s Your Vector, Victor?

On the other hand, vector graphics are composed of lines. Thousands of lines, either curved or straight. The vector data file for these images records the beginning and ending of each line, the colors around or inside them, and their curvature.

Corel Draw and Adobe Illustrator use vector images. Vector images are perfect for creating images with solid shapes and characters in them, such as a logo.

Raster vs. Vector

When to Use Them

On face value, there seems to be little difference between raster and vector, since they are both images. Even if they’re made with lines or dots, an image is still just an image.

Things get sticky when you consider the scalability of these two formats. First, take your tastefully rendered and perfectly crisp raster image, and blow it up to ten times its original size. The result is a very crude magnification of the original, since all the pixels are now ten times as large. Raster images don’t scale very well, and like this case, get blocky or very granular. A print prepared from such an image is a pretty disappointing product. As you can imagine, we avoid printing these designs, and are ready to help you scale your image properly so you can get a great print.

If you are committed to the raster format, you need to make a different resolution image for every size of this image you plan on using. That’s a perfectly good solution, although costly. Depending on the intended use of the image, it’s absolutely necessary. You’ll have a difficult time getting a vector image with similar definition and subtlety.

For comparison, scale up your vector image by the same power of ten. The result is the same image, but larger. No change in resolution. For this reason, vector images are very efficient for a variety of graphics. They lack the sophistication to make the fine color changes that we take for granted in a photograph, but advances in software are increasing the power of vector images all the time.

Use vector images for anything that doesn’t need photographic detail. That includes a logo or maybe a simple cartoon. These won’t suffer from the vector format, and they are infinitely scalable, so you only need one version.


Raster Image Progression



Earlier, we mentioned making different raster images for different sizes. This happens all the time, for people who need to see that detail at every magnification of an image. If you have a single image that is on your website, your T-Shirt, the side of a company vehicle, and is an icon for a social media site, it’s inappropriate to use the same raster file for each one.

The solution is to use an image scaling algorithm, and that is true geek territory. This is the realm of graphic designers, and though it seems like a simple thing to do, it’s actually quite complicated.

If you’re ever in doubt as to the scale and size of your image, it’s best to overshoot the target. A large image never suffers from scaling down, but as you’ve seen, scaling up a small image is problematic. For shirts, scale your images to the print size, or larger, and we can resize it.

Layers of Complexity

When it comes to making prints, we can use both raster and vector images. It’s even possible to use both kinds of files in the same image, albeit in different layers.

If you’re not sure about the suitability of a raster file for a custom print, take a look at the resolution on it. Generally, this is prescribed for a specific size. A good way to test it is to play around with the size of the image on the computer. If it looks grainy or blocky, the resolution isn’t going to work.

If the image and your print size match up, there’s nothing to worry about. If you’re not sure, or you think a raster image needs scaling, send it to the art department at DFC, and we can start talking solutions. We’re fully equipped to help you make the correct size print with a sharp image, so we’d love to hear your concerns.

And now, when you do make the call, you can share your new understanding of image techno-speak and impress the art department.

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