Frequently Asked Questions
This is where you will find
the answers to some of the common questions we are asked and also some
definitions of various acronyms and terms used in the graphics industry.
Please feel free to email through any corrections to errors that you may
find as this site by no means claims to be the final answer.
Resolution
Resolution is a measurement of the output
quality of an image, usually in terms of samples, pixels, dots, or lines
per inch. The terminology varies according to the intended output
device. PPI (pixels per inch) refers to screen resolution,
DPI
(dots per inch) refers to print resolution, SPI (samples per inch)
refers to scanning resolution, and LPI (lines per inch) refers to
halftone resolution.
Often images are referred to as high
resolution (hi-res) or low resolution (low-res). High resolution would
be an image intended for print, generally having 300 samples per inch or
more. Low resolution refers to images only intended for screen display,
generally having 100 pixels per inch or less.
Vector
A vector image is one of the two major
graphic types (the other being bitmap). Vector graphics are made up of
many individual objects. Each of these objects can be defined by
mathematical statements and has individual properties assigned to it
such as colour, fill, and outline. Vector graphics are
resolution
independent because they can be output to the highest quality at any
scale.
Software used to create vector graphics is
sometimes referred to as object-based editing software. Common vector
formats include AI (Adobe Illustrator), CDR (CorelDRAW), CGM (Computer
Graphics Metafile), SWF (Shockwave Flash), and DXF (AutoCAD and other
CAD software). Vector graphics tend to have much smaller file sizes than
raster-based bitmaps.
Bitmap
A bitmap (or raster) image is one of the
two major graphic types (the other being vector ). Bitmap-based images
are comprised of pixels in a grid. Each pixel or "bit" in the image
contains information about the colour to be displayed. Bitmap images
have a fixed
resolution
and cannot be resized without losing image quality. Common bitmap-based
formats are JPEG, GIF, TIFF, PNG, PICT, and BMP. Most bitmap images can
be converted to other bitmap-based formats very easily. Bitmap images
tend to have much large file sizes than vector graphics and they are
often compressed to reduce their size. Although many graphics formats
are bitmap-based, bitmap (BMP) is also a graphic format.
