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We evaluate the quality of the TFT display
with the help of a program called Nokia Monitor Test. The software
application displays a range of colours and test patterns that can help
diagnose just about any visual problems or defects a TFT display may
contain. It can also be a very useful tool for properly adjusting a
display to the correct settings. The software consists of eleven tests
which can be run in steps as adjustments are made to the OSD. As the tests
are run we look for the following problems, only one of which should be
inoperable (broken pixel).
Broken Pixels: What we class as a 'broken pixel' can
fall under any one of the following circumstances: Pixel always on (any
colour), pixel always off, pixel unable to display a shade (red, green,
blue, black, white), pixel shown colour gradient.
Pixel Clock: If the number of dot clocks within one horizontal synch are not
properly configured the screen will appear to drift or vertical stripes
may be generated. This should be correctable by the on screen menu.
Phase: If
the phase of the display data and dot clock are not correctly tuned the
screen can flicker, or text be displayed blurry. For example text may
appear dithered, or when looking at a test pattern of a one-pixel black,
one-pixel white checkerboard pattern the pattern may be distorted. This
should be correctable by the on screen menu.
Response Time: We look for any streaking associated
with moving a full page of text up or down quickly. Displays with slower
refresh rates tend to show some degree of image streaking or text
discoloration which can be distracting.
Stand Stability: TFT displays are fragile components and the
stand should offer adequately stable support as well as be easily
adjustable.
We deduct marks for quality control if there are any predominant
broken pixels in a display. While many manufacturers may consider a
few broken pixels acceptable, we believe the high cost of TFT displays
should translate into a clear and unblemished
image. |
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