An explanation of Raster vs Vector

[Kool]

The folowing is one of the best explanations of Raster vs Vector images I have ever read. Contributed by our own Keyare.



Photoshop is raster based.



You never do logos in photoshop unless everything you do is either on the web or in full colour - even then it's rare.

Here's a logo you'd recognise. You might think it's photoshop but it's all vector. Every line is just point connected with an angle of a curve, a vector. That way you can scale them to the size of the moon and you won't lose a single detail. If a curve is closed (both ends join) then you can fill it with a color. Many different closed curve layers on top of one another can imitate a graduated screen or color ramp like photoshop would do. You can't do really complex or photorealistic things in vector without spending days doing it, but in a logo you want simplicity anyway.

Below is the wireframe of a logo, followed by the same vector - filled with colors.







These files are usually shared as EPS format. They're incredibly small and easily distributed over the internet because of their size. you only record the point on the lines, their angles and

what color they are filled with which is usually much less data than a raster image.



This is a closeup of a raster image, you'll know this from photoshop. A raster image is made up of pixels (little squares) with a numerical value for their color. All the squares are the same size and places in a grid pattern. Each one needs at least three numbers (for RGB) to calculate it's color (4 for cmyk and 1 number for 8 bit colour like a gif) unless there is compression (like a gif, where large areas of the same color are assigned a beginning and an end point and the color value is assigned only once, or jpg's where an area of 8 or more pixels are assigned one of many algorithms built into the jpg codec).

Raster images cannot be scaled up in size because they will look pixelated (like the image above) when printed. And files that are high enough resolution for the printing process are usually very large. We use these for photographs or completed files when we can output a raster image at exactly the size required for printing.

As a vector, any colors can be assigned to the curves, including rgb, cmyk and spot colors. You could have a logo as pantone 567, pantone 490, 303 and more... In a raster you usually use a CMYK color model or RGB. Sometimes you'll run across a duotone or tritone but these are not very common and definitely will not be usable in most office programs.

Gif and jpg are great for small office programs and for use in a little office type setting but for printing on a press, proper graphic design, signage etc. you'll need a vector based logo so that the outfit can work with it and have the cleanest image possible.

You'll also need to be able to create logos that can be easily printed in one or two colours. Your clients might have a wonderful red-on-black 3D logo, but try printing it in the newspaper in one color and it will just be a solid black mush.

As far as what you create for your clients - it's as simple as asking them. Do they just want a logo and they'll do all their own letterhead etc. themselves or do they want a full package? Charge accordingly. Sometimes if you just do the logo you can get more business by showing a sample of a card and/or letterhead design and telling you'll do additional design for only $X more. And sometimes you're just shooting yourself in the foot too!

The best thing is to always set up the rules of the game BEFORE playing it.

[DavidLieb]

Here's another way of putting it (taken from my school's courseware):


<A name=_Toc87432453></A><A name=_Toc87088758>There are two different types of images used by graph design programs: raster images (sometimes called "bitmap")and vector-based images.</A>
Photo Editors are Raster Based</o>
A raster image is made of thousands of little dots, or pixels.
Creating or editing an image with dots allows you to provide for rich detail in an image. Because every dot can be a different color, you can allow for any kind of color change.
Raster images are wonderful for rendering rich, full-color images, like photographs. Raster-based programs do have some drawbacks, though:
* Raster images are file-heavy. All of the zeros and ones that are used to make up each pixel result in large files sizes. Your computer must keep track of the zeros and ones and must change each one when editing. This is memory-intensive and may cause slower editing.
* Rasters do not resize well. When you resize a raster image, the pixels just get larger, making the image appear distorted and chunky/grainy.
Photo editors, like Adobe PhotoShop, use raster-based images to allow for precise editing and total freedom in image appearance.
</o>
Illustration Programs are Vector Based</o>
Vector-based programs approach image creation in an entirely different manner. A vector-based program does not render images on a pixel-by-pixel basis.
In a raster-based image creation program, a square would be made of thousands of pixel dots.
In a vector-based program, the same square would be made of only four dots, one on each corner. These “vector points,” basically allow your computer to play Connect the Dots. Each vector point has information in it telling your computer how to connect each point with straight or curved lines, and with what color to fill in the closed shape.
In the printed image, the vector points would be invisible.
Because the computer only has to keep four points in its memory, it is much easier for the computer to edit vector-based images.
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. You can easily color, or recolor, a vector-based image very easily using a drawing program. Vector images can also result in smoother lines because the lines are not hand drawn.
Vector images do have some drawbacks, however. They are generally filled with a solid color or a gradient but can’t display the lush color depth of a raster. They also work better with straight lines or sweeping curves.
Drawing programs, like Adobe Illustrator and Macromedia Freehand, primarily use a vector-based drawing mode to allow for scalability and clean lines.
</o>




David Lieberman
Academy of Web Design Course Video
Add Web Design to your Skills!

Post Edited (DavidLieb) : 12/14/2004 5:49:27 PM GMT

[photodesign]

Here is a very long article I wrote on just this subject, taken from one several of my lectures: http://freerangestock.com/understanding/vector_bitmap/

[PrintDriver]

I notice now he said Illustrator primarily uses a vector-based drawing mode.
All of the illustration programs today use raster effects to create some elements. Fuzzy dropshadows and outer glows that you can do in Illustrator are Raster Effects and scalability is dependent on how they are applied.

[SEP Studios]

I like to keep things simple:

Raster = pixels
Vector = curves

Scott

[urstwile]

This video has a different way of explaining it, I thought the analogies were pretty good.

[decarle]

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


RASTER:
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:
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.

[LittleRed]

So you said very rarely would you use Photoshop for logo creation. I assume then that you use Illustrator?

Sorry if that's an amateur question, but I was just wondering as someone commented saying that it too was a raster based program? Never having used it I am unsure.

[CkretAjint]

LittleRed, that is correct. Adobe Illustrator is a vector based program.

[PrintDriver]

Illustrator is vector based but it does contain some raster effects (ie drop shadows, glows and some transparency interactions). Your job as a designer is to know the difference.