SED618 Graphics Write Up
1. How important are graphics to web pages?
Graphics are increasingly important to web pages. In the early days of
the Web, graphic downloads were slow, say, 14.4kB, making any but simple
graphics prohibitive. Hence what graphics there were needed to be
small. There was also the issue of display -- different computers
showed images differently, including colors. It was not uncommon for
users to disable the display of graphics for speed's sake.
The reading is prologue to today; we have greater resolution, deeper
color spaces and more commonality enforced by browsers. But design
principles are consistent. Today, a "graphically challenged" website is
likely to be overlooked or skipped. Good design is essential today.
2. What is different about web graphics?
Web graphics are much lower resolution than traditional print
resolution. Commercial print starts at 1200 dpi and goes up from
there. Web graphics are at 72dpi. Also, with print graphics, the
designer can count on the appearance and color representation of the
final product. The designer may have to deal with differences between
his or her screen and the paper product, but once printed all users will
see the same image. The web designer is obliged to target multiple
platforms; PCs are said to display colors somewhat more darkly than
Macs. Unix machines are off on their own. Target resolutions differ
too, offering more or less resolution. The designer needs to be aware
of these variations in order to produce the most universally accessible
pages.
3. What are the different formats of graphics? When should you use each?
The article cites the choice of GIF and JPEGS. Both are lossy
compression techniques. JPEGS are good for continuous tone images with
small color changes. They're not as well suited for cartoon art with
solid color. GIFs only display 256 colors.
4. What are the file types for video? When are they used best?
Three types of video are described in the reading. AVI is PC-specific;
QuickTime comes from Macintosh. Readers are available on each platform
for the "opposing" format so each can be said to be universal. The
third type of video format is MPEG. A drawback is that MPEG sometimes
comes with separate files for audio and video. Another drawback is that
MPEG is compute intensive to create. However, hardware is available to
accelerate this process. All that said, MPEG is one of the best looking
formats.
Within the video formats we have the issue of codecs. These are the
engines used to perform the actual compression.
5. What are the file types for audio? What factors do you need to be
concerned with?
The four types discussed in the article are AIFF (Mac), WAVE(Windows),
MPEG and Real Audio. The factors we're concerned with are the bit depth
and sample rate. When recording, it is good to record at high
resolution: 16 bit stereo, 44kHz. To deploy on the Web, the audio can
be "de-rezzed" to a lower quality setting to decrease file size. The
relationship between file size and sample rate is linear. Speech may be
satisfactorily rendered at 22kHz or even 11kHz.
Open Questions:
How does MP3 compare to the formats discussed in the reading? Have
display platforms become more uniform in color and size then they were
in the reading?
