Extron Electronics IN1408 - Manual (Page 27)

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IN1408 Operation Manual - V1.4 3/21/02 12:32 PM © 2002 - INLINE, Inc.
Choosing the Optimal Output Resolution and Refresh Rate
Of all the settings on the IN1408, perhaps the most critical adjustment is the output resolution and
output refresh rate. Every display device has an optimal or native resolution and an optimal
refresh rate. This will vary depending on the type of display technology, if the display has a fixed
number of display elements (native resolution), the size of the pixels, the size of the display or
display screen, and even the distance of the viewer from the display screen. Setting the IN1408
to the output resolution and refresh rate to match this optimal resolution for your data display will
have an enormous impact on the image quality.
Please note that the ideal resolution must also lie within the compatible scan range of the display
device. For example, some 27” – 36” presentation monitors are limited to input signals in the
30 – 50 KHz range. If the video scaler’s output resolution and refresh rate settings are too high
the signal will not be viewable on the display. Before selecting the output resolution and refresh
rate, you should check the specifications page in the operation manual for your display device to
verify the compatible horizontal scan range and vertical refresh rates. You may also be able to
find this information in the INLINE PRODUCT CATALOG reference section. The Large Screen
Data projector list and Large Data Display list include signal compatibility information for both
current and obsolete models of data projectors, retro displays, presentation monitors and plasma
displays.
CRT DISPLAYS – SELECTING THE GOLDEN RESOLUTION
While CRT displays do not have a native resolution, they will have a “golden resolution,” or
sweet spot, for input signal resolution. When the video scaler is set to the golden resolution of the
CRT display, this will result in a sharp, detailed image without visible scan lines. If the video
scaler is set below the golden resolution, the displayed image will have tiny black lines between
the image lines. If the video scaler is set above the golden resolution, the lines will actually
overlap and the image will appear soft and loose detail because there are more lines and pixels
than the display can clearly resolve. When experimenting to find the golden resolution for your
CRT display device it is best to set the output refresh rate at 72 Hz and begin at the output
resolution indicated in the chart on page 26. You can then try higher and lower resolutions until
you achieve the setting that offers both a solid image and excellent picture detail.
CRT DISPLAYS – SELECTING THE OPTIMAL REFRESH RATE
CRT displays may tend to flicker at refresh rates below 70 Hz. In order to achieve a solid,
flicker-free image, an output refresh rate of 72 Hz or 75 Hz is recommended for most CRT
displays. You should also experiment with even higher refresh rates to see if they create a better
image. In some cases, you will find that the image suddenly appears better at a higher refresh rate
such as 85 Hz.
Keep in mind that as the refresh rate is increased, the horizontal scan rate also increases. This
places greater higher bandwidth demands on the video distribution system and the display device.
If you select a refresh rate that is too high you will actually see a softer image because the signal
is exceeding the bandwidth capabilities of the display device. Extremely high refresh rate
settings may also create a compatibility problem because a very high refresh rate may result in a
signal that is outside the compatible scan rate of the data display.