TFT Display Evaluation Notes
|PCstats TFT Display Evaluation
evaluate the quality of TFT displays 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 optimal 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
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
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.
|Display Test System
||ATI Radeon 8500 |
Windows 2000 |
||Color Temp: 6500 Kelvin|
|LCD Display Test
||Test Notes and Observations|
Excellent picture geometry at the 191T's native
1280x1024 resolution. The image is very
sharp, but curved lines are not exceptionally blocky as you might first expect.
|Brightness and Contrast:
Good clean shading but difficult to see the first
few percentiles (from 1%-3%). There is no ghosting or unevenness in
black background. Screen contrast is very high, and the blacks are very black,
not greenish as with some lower-end displays.
test is more applicable to CRT displays than it is to an
LCD. How ever since it forces the display to show a full screen of black or
white, while maintaining a solid white line around the outside it is a good indicator
of refresh rates on both the display and pixel levels.
The brightness of this display is very good, even
is only listed at 250cd/m2. When showing white screens the 191T appears brighter than our comparison
CRT. The red, blue and green test screens were all very bright and very consistent over the
full area. There was no visible dark patches, banding, or broken pixels.
The test grids in RGB illustrate the
worst case situations when different coloured pixels must work closely
together, and since they comprise different parts of a pixel they do not line
Excellent, all patterns are clearly visible and defined in both the
horizontal and vertical axis.
Resolution was also excellent at the native
1280x1024 resolution. Image dithering at lower resolutions
is also very good as with other Samsung LCD's we have
Excellent, all test patterns were displayed
properly and without interference or 'walking lines'. Properly adjusting
the image sharpness is critical in this area, as the auto adjust does
not always update this setting.
Other Evaluation Notes:
Like the 181B, the
pixel refresh rate for the 191T is 25ms. With
a set of viewing angles at 85/85/85/85 it is currently at the highest
standard available. The stand was very stable, although rotating left to right was
not smooth or easy - there was too much friction. The vertical height adjustments with this
stand are nice, and the tilting is easy to