Raster vs. Vector

December 1, 2014 amywaggs No comments

No, it’s not the newest superhero vs mad villain story!

Although that would be awesome.

Last month I talked to you about how important knowing what “resolution” was and how each photo is measured in units called pixels. This month, we’ll deal with pixels again, but we’re going to compare images created with pixels to images created with mathematical equations.

I totally just blew your mind didn’t I?  kapow

A RASTER image is an image made of hundreds (or thousands or millions) of tiny squares of color information, referred to as either pixels or dots.

The most common type of raster graphic? A photograph. The designer’s preferred program for creating and editing raster files? You guessed it: Adobe Photoshop.

If you’re wondering if that image file is raster, check it’s file extension. Rasters will be one of these: jpg/jpeg, psd, png, tiff, bmp and gif.

vector-raster

A VECTOR image uses math to draw shapes using points, lines and curves. So whereas a raster image of a 1” x 1” square at 300 dpi will have 300 individual pieces of information, a vector image will only contain four points, one for each corner; the computer will uses math to “connect the dots” and fill in all of the missing information.

The most common types of vector graphics? Fonts and logos. The designer’s preferred program for creating and editing vector files? Adobe Illustrator.

Popular vector file formats include: eps, ai and pdf. BUT, DON’T BE FOOLED. Photoshop (remember, Photoshop is a raster image program) can save files as .eps and .pdf too, so make sure you double check with your designer if you don’t own a robust image editing program.

superherosleepingIf you’re not yet asleep, I’ve provided a couple pros and cons for each file type. But if you’re dozing off already, just take this one piece of information away with you: ALWAYS have your logo designed in VECTOR. Please. And thank you.

PROS of RASTER

  • Rich Detail: Say you’ve got a 1” x 1” square image at 300 dpi—that’s 300 individual squares of color that provide precise shading and detail in your photograph. The more dpi, the more subtle details will be noticeable.
  • Precise Editing: All of those individual pixels of color information can also be modified, one by one.

CONS of RASTER

  • Blurry When Enlarged: The biggest downfall to raster images is that they become pixelated (aka grainy) when enlarged. Why? There are a finite number of pixels in all raster images; when you enlarge a photo, the computer takes its best guess as to what specific colors should fill in the gaps. This interpolation of data causes the image to appear blurry since the computer has no way of knowing the exact shade of colors that should be inserted.
  • Large File Size: Remember how a 1” x 1” square at 300 dpi will have 300 individual points of color information for the computer to remember? If you have an 18” x 24” photo— that’s 129,600 bits o’ info for a computer to process which can quickly slow down even the fastest machine!

PROS of VECTOR

  • Infinitely Scalable: Through the wonders of math, vector files can be scaled up or down as much as you want without losing any image quality.
  • Smaller File Size: Using our previous 1” x 1” square example, a vector file needs only four points of data to recreate a square versus 300 individual pixels for a raster image. (Meaning a much smaller file size and faster processing speed.)
  • Edibility: Unlike popular raster-based formats, all of the original shapes exist separately on different layers; this means you can modify individual elements without affecting other objects in the image.

CONS of VECTOR

  • Limited Details: Because of the mathematical way that a vector remembers data, they are not practical for complex images that require exact coloring. Sure, you can create basic color gradients, but you’ll never be able to match the color detail available in a raster image where each individual pixel can be its own individual shade.
  • Limited Effects: By definition, vector graphics are created from simple points and lines. This means they can’t handle certain styling effects, like blurring or a drop shadow, that are available with raster images.

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