A basic guide to digital images

Updated: Mar 27, 2019

Not all digital images are the same. You've seen it. There's a virtual alphabet soup of file types out there, such as .png, .jpg, .jpeg, .gif, .svg, .eps, .ai, and .pdf. What does it all mean? Fret not - we're here to help.

Two Basic Types of Image Files

What do all of those file types on images mean? Really, that's not what is important. More important to understand is that there are two basic types of image files: raster images and vector images.

Raster Images, or Contones

According to Wikipedia, "[t]he word 'raster' has its origins in the Latin rastrum (a rake), which is derived from radere (to scrape)." A raster image is just that - it is raked from a vector image to create a perfectly sized and dimensioned file for use by, principally, web browsers.

Indeed, it was the World Wide Web that popularized the use of raster image types, such as .jpg and .png, because those file types present better at smaller and mid-sized forms.

Raster images are great for making sure that images load quickly and correctly every time, regardless of device type. Raster images, however, as many of you know, most often print poorly for two reasons.

First, raster images do not scale. Their resolution does not adjust and the user will see pixels if they print an image at any size, but particularly if a user tries to print an image larger than the default resolution of the image.

Second, raster images are comprised of three principal colors: Red, Green and Blue (RGB). Our computers and mobile devices present the world to us in three colors. But, our world, is presented in four colors: Cyan, Magenta, Yellow and Black (CMYK).

For professionals working in the pre-press and printing industries, the standard is to print with vector images and high resolution raster images in a CMYK color set to ensure the highest quality print possible for your product, whether it be custom decorated apparel or direct mail produced by offset lithography (shout out! to our friends at Valley Offset Printing, our source for offset lithography in South Central Kansas).

Vector Images

Vector images are a shape or series of shapes and lines that create perfectly scalable images.

Vector images are mathematical equations that automatically scale without losing resolution or print quality. Vector images, likewise, can be set to any color or combination of colors, such as Pantone® colors or four-color process colors (Cyan, Magenta, Yellow and Black).

"Vector graphics are computer graphics images that are defined in terms of 2D points, which are connected by lines and curves to form polygons and other shapes. Each of these points has a definite position on the x- and y-axis of the work plane and determines the direction of the path; further, each path may have various properties including values for stroke color, shape, curve, thickness, and fill." Wikipedia

Understanding the alphabet soup of file types

In order to understand what all of those file types mean, we created a simple (raster) graphic that sorts those file types into their vector or raster type. Generally speaking, if the image is a file you saved from a web browser, it is a raster. However, the World Wide Web Consortium does recognize the SVG file type - or scalable vector graphic - as the standard for certain image files on the web (traditionally, corporate logos and branding files that must scale with responsive websites).

Which image type is best?

The answer to that question is: it depends on application.

In the decorated apparel and garment industry, such as screen printing and embroidery, we rely principally upon vector graphic art to produce our screens and digitized embroidery files.

Unlike other screen printers in Wichita and the region, we never charge you for preparing your graphics and images for print, including the conversion of raster images to scalable vector graphics that screen printers require to print.

For us, because we already run a full-service graphic design shop, this work is easy and part of what any good screen printer should do for their clients.

If you have an art file that needs some work or are interested in printing your corporate logos on some t-shirts for the summer co-rec team, contact us and we'll get your art prepared for print without additionally hourly charges or ridiculous and arbitrary revision limits.

Our only goal is to see you happy with the final product.

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