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What the heck is a vector file?

Raster and vector are two different types of digital graphic files, each serving a specific purpose. Understanding the differences is important to achieve your desired outcome.

Raster

Raster graphics are images made up of tiny dots or pixels, which contain colour information. While the terms are often used interchangeably, the technical term for this
blog_raster_cropinformation when referring to an image displayed on a monitor is pixel and dot refers to the same bit of information on a printed image.

The most common use of a raster file is photographs. You may have heard reference to a photo as 300 dpi or 72 dpi, this refers to the quality of the photo. A 300 dpi, dots per inch, photo has a higher resolution and higher quality than a photo with 72 dpi. High resolution photos will print sharper than photos with low resolution because there is more information in one square inch of the photo, there are more dots per inch.

Why don’t images from the internet print well?

There is nothing worse then waiting for an image to load onto a webpage, agreed? Typically when this happens, it’s because the image is a higher quality than it should be for its purpose. In order for images to appear in focus when viewed on a screen and not keep you waiting, they should be formatted to 72 dpi. As mentioned, 72 dpi is low resolution for a printed photo which is why photos from the internet do not print well.

It is possible to decrease the number of dots or pixels and size of a raster image or graphic without losing quality, however the conversion does not work the other way.

Raster files used for print will contain one of the following extensions:

.psd – Photoshop Document – is a layered file created in Adobe Photoshop. This file format makes it possible to edit individual layers of the image even after the file has been saved.

.tif/.tiff – Tag Image File or Tag Image File Format – is similar to a .psd file in that it keeps individual layers separated even after saving, but a .tif can also be opened by programs other than Photoshop. A .tif has the ability to save transparencies and has a slightly smaller file size than a .psd without compromising quality, taking up less space when being stored.

.jpg/.jpeg – Joint Photographic Experts Group – is the most common format for digital photos. This file type has “lossy” compression, which means that some image quality is lost when the file is saved. This slight loss in quality results in a smaller file size making it easy to transfer electronically. A .jpg does not maintain layers after saving.

.eps – Encapsulated PostScript – are acceptable for print but are a less common format today, as there is no real benefit to them over the other formats available.

HELPFUL HINT: It is possible to save both raster and vector files as an .eps. If a vector file is required, a raster .eps will not suffice. Be sure to clarify what type of file is needed not just the extension the file should have.

Vector

Vector graphics and images are a combination of geometric shapes, point, lines, and curves, based on mathematics instead of pixels. Having a mathematic relationship between elements blog_vector_cropallows them to be resized without losing quality. Vector files are typically editable, provided the text hasn’t been converted to outlines and raster images haven’t been placed within the file without being embedded.

TIP: If using raster images in a vector .eps file, be sure to embed the image or include the linked image when transferring the vector file.

Vector files are particularly important for logos. As a best practice, always design logos using a program that will produce a vector file.

Vector files will end with the following extensions:

.ai – Adobe Illustrator – is a vector file created in Adobe Illustrator. All elements and layers are editable even after saving.

.eps – Encapsulated Postscript – is similar to an .ai file but can be opened by programs other than Adobe Illustrator. (See Raster .eps HELPFUL HINT)

As you can see there is more to a file and its extension then you might expect. Each file type has a unique purpose. Simply changing the letters of an extension will not change the properties of the file itself. When it comes to digital graphics, it’s a good idea to start with the end in mind to avoid wasting time recreating or reformatting files.

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