Vector vs Raster

What's the difference between a vector and raster file?

If you think of raster file like a digital photograph, a vector file is like a tracing of that photograph. 

In this analogy, a photograph is taken with a fixed resolution.  It has a certain number of pixels to contain all the information necessary to display its image.  When you look at the photo from one distance it appears in-focus.  As you move closer, the boundaries from one feature to the next are obscured by a color gradient of pixels between the features.  If you have ever zoomed into a digital image to trace it, you definitely understand.  You must decide which pixels should be included and which should not.  Even on a true black and white image, the contour of features becomes a jagged or speckled line.  The software used to program the laser has to trace this image and runs up against the same challenges.

Sticking with this traced photographed analogy, a vector image is the trace result if you were to use an infinitely fine tipped pen.  The traced image would be made of lines with no width, only start and stop points on an XY plane.  They would include a radius value if curved.  It's mathematical geometry that can be scaled without loss of clarity. 

 

How does this relate to laser cutting & engraving?

Except when engraving a photograph, a vector file is preferable.  Think about logos, text, and silhouettes.  That's because you'll submit a file and likely want it scaled to a different size before processed at the laser.  This is especially true for work containing logos or text where shapes are less organic in nature.  What looks good on a computer screen may not look good once cut if starting from a raster file.  A raster file will lose sharp corners and crisp detail the more it's increased in scale.  When engraving a photo, this is unavoidable.  Starting with the largest and highest resolution image will improve the results when engraving a photo.  

What's the difference between cutting and engraving?

Cutting and engraving are accomplished by entirely different head movements.  When cutting, the laser head takes a vector path.  It moves along a defined line.  By contrast, engraving is done by moving the head back and forth from one side to the other perpendicularly moving by a set increment.  The entire image is covered by the path of the beam in order to discolor or remove material.  Cutting a shape is consequently faster than engraving in most cases.  

Which file types are which?

Most common vector file types.

DXF
DWG
AI
SVG 

Most common raster file types.

JPG
PNG
BMP
TIFF
GIF

These file types can be either raster or vector

EPS
PDF