What are vector graphics?
Vector graphics are illustrations which utilize shapes (points, lines, curves) based on mathematical equations whereas raster graphics (such as JPG and PNG)
are based on a finite number of pixels (such as "6 megapixels" which means approximately 6 million pixels, or 2112 x 2816). Pixels spread out when
an image is enlarged, therefore there is a size limitation when printing a raster image. Image quality is reduced significantly if you go very much below 100 dpi (dots per inch).
(Download a small web graphic, enlarge it 500%, and there's a good example of what happens.) Vector graphics,
however, can be printed at any size without loss of quality. The vector graphic file is basically a series of mathematical equations and instructions
which describe how to create the image.
Click here for an example.
Simply obtaining a vector graphic, may not be enough to let you print a billboard or wall mural. First you'll have to rescale the image to the desired
print size and may have to re-convert it into another format such as JPG, PDF or PNG at the new enlarged size. Then you'll have to divide it up into pieces, print each individual
piece of the image, then reassemble it on your billboard or mural. Although there may be some printing processes I'm not aware of which will let you
directly print a vector graphic at a specified size.
How do I calculate DPI for raster images?
Calculating dots per inch, is easy. You just divide the pixel size of your image (a 6 megapixel image is 2816 x 2112) by the desired dpi to get
your print size in inches. For example, printing a 2816 x 2112 image at 100 dpi will result in a 28.16" x 21.12" print.
DPI is often overrated, however. While 300 dpi is often considered the standard for high quality printing, the average person looking at a 200 dpi
photo print side by side with a 300 dpi photo print could not see a difference. Additionally, the distance from which you will view an image can allow
a less than perfect image to look nearly perfect. While a postcard or greeting card should be printed at 200 to 300 dpi, a poster can be below 100 dpi
and still look good since it's viewed from a distance. If you need an especially large image from a raster graphic that would require you to print it
at below 85 dpi, that's the circumstance where you should convert your raster image into a vector graphic.
Are vector graphics programs expensive?
The famous ones like Adobe Illustrator and CorelDraw are. But there is a
free vector graphics program
called Inkscape which lets you create SVG (scalable vector graphics) and EPS (encapsulated post script) files, as well as PDF and other formats.
At first glance Inkscape may mystify you, but if you do Google and other search engine searches for terms like HOW TO USE INKSCAPE you'll find some
helpful information.
