Video and data projection
What you should know about scan rates
Why
do many projector and monitor manufacturers specify scan rate
ranges as well as resolution? Don’t they mean the same thing?
The scan rate ranges
offer a more exact way of specifying whether your projector or
monitor will match up with a particular PC or workstation.
The reason is that
a computer outputting a particular standard (SVGA for example)
can be anywhere within a range of scan rates, and the scan rates
will vary from brand to brand. Yet your projector must be able
to lock on to the particular scan rate your system is outputting.
Sometimes that can be a problem if your computer is at the high
end of the range; it can also be problematic if you’re using an
engineering workstation with a non-standard output.
| The most commonly used
scan rates |
| Resolution |
Horizontal
frequency range |
Vertical
frequency range |
| CGA |
15.575
Khz |
60
Hz |
| VGA (640 x 480) |
31.5 - 43 Khz |
60 - 85 Hz |
| SVGA (800 x 600) |
32 - 54 Khz |
50 - 85 Hz |
| XGA (1024 x 768) |
48 - 80 Khz |
60 - 100 Hz |
| SXGA (1260 x 1024) |
52 - 80 Khz |
50 - 75 Hz |
|
