File Resolution
Resolution
Resolution pertains to how sharp and clean an image
looks, and how much detail you can see. In low
resolution fine lines may look coarse, and curves
are jaggedy. The higher the resolution, the less
coarse and jaggedy the image will appear.
What is File Resolution?
When an image is digitized (usually by a scanner or
digital camera), it is done at a specific
resolution. The building blocks that make up a
graphics file are called pixels, just as an image
on a monitor is made up of monitor pixels. The
resolution of an image file is measured in spi
(samples per inch), although "dpi" (dots per inch)
is very often used in place of "spi."
On screen
How clearly an image is "resolved" on a screen
depends on how easily the computer can fool our
eyes. When there are many shades or levels of gray,
or numbers of colors, our eyes can't tell very
easily where one blends into the next. The image
appears more resolved than it would be if it were
made of only black and white pixels.
For paper
To get a printable scan with rich detail, or create
a richly detailed image from scratch, you need a
lot of pixels to work with. Saving an image at low
resolution (say, 72 dpi) will not produce
acceptable results when the image is sent to an
imagesetter for output on film for printing.
Usually, images that are scanned for output on
paper are saved at a resolution of at least 300
dpi.
For Web
A typical screen resolution is 72 dpi and a
high-resolution image is often 300+ dpi. You should
always work at "screen resolution" when authoring
images for the Web (or any screenbased medium such
as television or interactive multimedia). The
accepted measurement of "screen resolution" is 72
dpi, or 72 dots per inch. This is because most
standard computer monitors use 72 pixels for every
inch of screen space.
References:
- Webster, Timothy. Web Designer's Guide to Graphics PNG, GIF & JPEG. Indianapolis, IN: Hayden Books, 1997.
- Weinman, Lynda. designing web graphics 2: How to Prepare Images and Media for the Web 2nd edition. Indianapolis, IN: New Riders Publishing, 1996.
- Williams, Robin with Steve Cummings. Jargon, An Informal Dictionary of Computer Terms. Berkeley, CA: Peachpit Press