What is Difference between VECTOR and Raster Graphics

 There are two main type of image files: Raster and Vector. 

What is DPI?

DPI stands for "dots per inch" and PPI translates to "pixels per inch." These units of measure are essential for determining if the density of pixels in an image is appropriate for the application you are using.

If you are using an image for print or web. Websites display images at 72dpi, which is low resolution; however images at this resolution look really crisp on the web. This is not the case for print. Best practices for printing an image will require it to be no less than 300dpi.

RASTER GRAPHICS:

Raster images are made of pixels. A pixel is a single point or the smallest single element in a display device. If you zoom in to a raster image you may start to see a lot of little tiny squares.

The greater the ppi and dimensional measurements, the higher the quality. Most printing projects require images to be at least 300ppi, for example.

Let’s say you’re printing a brochure, and you need a background image to span the entire unfolded interior: 8.5”x11”. Your background image should be at least 2,550 pixels wide (8.5 inches) by 3,300 pixels tall (11 inches) with a resolution of 300ppi.

Raster images cannot be scaled to larger sizes. When they are scaled, quality is lost and they become blurry, as each pixel becomes larger or photo editing software attempts to compromise by adding in colored pixels.

VECTOR GRAPHICS:

Vector images are mathematical calculations from one point to another that form lines and shapes. If you zoom into a vector graphic it will always look the same.

Because vectors can be infinitely scaled without loss of quality, they’re excellent for logos, illustrations, engravings, etchings, product artwork, signage, and embroidery. Vectors should not be used for digital paintings or photo editing; however, they’re perfect for projects such as printing stickers that do not include photos.

When use Vector & Raster?

If the file contains a lot of gradients or hues — raster should work better 

vector graphics are perfect for icons, logos and 2D graphics 

Example:

When should you use raster or vector?

Raster images are best for photos, while vectors are best for logos, illustrations, engravings, etchings, product artwork, signage, and embroidery. Some liken raster images to paintings and vectors to drawing; if your project requires complex color blends, such as in painting, raster is the preferred format; if your project requires scalable shapes and solid colors, such as in drawing, vector is the best choice.

Many projects combine raster and vector images together: a brochure, for example, might include a corporate logo (vector) and a photo of happy customers (raster) – often coupled in layout software such as InDesign or QuarkXpress (though Illustrator and Photoshop can also be used to pair raster and vector images).

Other examples include printing postcards that feature an illustrated background (vector) with a foreground photo (raster), online catalog printing that features scalable product information tables vector) alongside product images (raster), and business greeting card printing that combines corporate logos (vectors) with photos (rasters).

Ultimately, it boils down to what you’re creating and its intended use. If you need a brand logo that will be used time and again in multiple media – print, digital, television, product etching, signage, etc. – you should create a vector that can be scaled as-needed, then output in whichever format you need at any given time. If you want to edit a photo or make a sweet digital painting, you should create a raster that’s capable of rendering complex color blends and mimicking the natural qualities of light.