Raster Images vs Vector Images: An Explanation

Stationery Direct

Staff member
There are 2 different types of images used by graphic design programs, raster images and vector images.

A raster image is made up of thousands of little dots/pixels, photo editors such as Adobe Photoshop are raster based and are great for rendering rich, full colour images like photographs. Raster based programs do have some drawbacks though:

> Imagine a square 1 inch x 1 inch, if this square has been created at 300dpi then this will have 300 dots/pixels within it. The computer must keep track of all the zeros and ones that make up those 300 dots/pixels, this can result in large file sizes which can be memory intensive when editing, the spec of your PC/MAC will determine if this causes you problems or not.

> Raster images do not resize well, when you resize a low resolution raster image the pixels just get larger making the image appear distorted and blurry. One solution to this is to ensure the image is created at high resolution, an image at a minimum of 300dpi will resize quite well and keep fairly good clarity, however, it will only enlarge so much.

Vector based programs such as Adobe Illustrator approach image creation in an entirely different way and do not render images on a pixel by pixel basis. Using the same example as above the 1 inch x 1 inch square would only be made up of 4 dots/pixels, one on each corner. These “vector points” allow the computer to play connect the dots, each vector point has information telling the computer how to connect each point with straight or curved lines, and what colour the inner space should be.

Because the computer only has to keep four points in its memory, it is much easier for the computer to edit vector based images as file sizes are really small. If you resize a vector based image it loses little or no detail, the vector points spread out and the computer just redraws the image. Vector images are ideal for logos as they can be resized and adjusted without losing clarity, so when looking for a logo designer ensure the final files produced are vector based.
Thanks for that useful info, much appreciated. I knew the basics but that extra bit of knowledge will help when trying to explain the difference to clients.

Thank you!
As an experienced artworker I thought it may be worth mentioning that vector files can have a threshold of complexity for usable file sizes.

An extremely complicated .ai file can easily be over a 200mb in size, and will have issues printing properly as it can kill the RIP.

It can also make working in InDesign quite slow and running out to a laser.

.ai and .eps files can get this big when there are a lot of paths, blends and gradients being used.

When vector files get over 100mb or so I tend to rasterize the vector file in Photoshop to the required print size and drop the new bitmap in place of the vector file.

Hope that helps.
Lets not forget that there are smart arses out there who like to embed huge raster files in their vector files and not mention the fact to the poor mug who has to print it.:icon_eek:
The difference between vector and raster graphics is that raster graphics are composed of pixels, while vector graphics are composed of paths

This is really the fundamental difference, and the first thing you need to understand.

Second, I'd say is that for raster format images (like jpg, png, tiff etc) what matters is the number of pixels it has. The "resolution" of a raster image is just the number of pixels divided by the size you decide to print it at (which can be anything). So a raster image in itself doesn't really have a fixed resolution (like 300dpi) it only has a set number of pixels, and for some formats an arbitrary value you can set as a print size to calculate a resolution if you print it at that size. This arbitrary "print size" is used as a default if you place it in Illustrator etc, but you can then just change it. So, "send me a 300dpi image" doesn't really say anything except that they probably want something with a lot of pixels. While, "send me a 10x10inch image at 300dpi" or the easier "send me a 3000x3000px image" actually says something about the image they want.

Third, as dogsbody pointed out, all vector graphics formats I know of (like svg, eps, pdf) also support embedding raster images. So while you can be sure from the format that a file is a raster file, you can't be sure something is a pure vector graphics file from the format.
let's not forget that its dpi for printing and ppi for the screen.

raster images use pixels and vectors use a range of nodes (points)

add if you are unclear you may have node idea what I mean :)
I get this question so often that I wrote a blogpost about this with some interactives in it to see the difference in zooming and sharpness between the two. This might help people here.
Here you can see clearly that you can zoom in on vectorgraphics endlessly with the image remaining it's sharpness. Personally I absolutely love vectorgraphics, especially for making illustrations and interactives, but there are also some cons to using vectorgraphics. These are also in the article.

English: What's the difference between Raster and Vector Graphics?
Dutch: Wat is het verschil tussen Raster en Vector Graphics?
As a new member, and as a beginners photoshop user, this was the great explanation for me to understand the Raster and Vector. Thanks to the Admin.
Raster images/bitmaps are made up of pixels. Each pixel is dedicated to color. This is why, when you zoom in, you'll find the image to be pixelated. Vector images are made up of paths, each with a mathematical formula telling the path how it's shaped and what color it is filled with. And so, because of this, even if the picture is zoomed in or resized, the image retains its shape.
Pixels vs paths basically. If you want to be able to scale the graphic up ideally you need a vector graphic to prevent quality loss. If you need to create a complex design full of shading, colours and gradients then use a pixel based graphic.

If you need any more free advice please drop me a line at iAM Graphic Designer