Read on for an
understanding of monitor specifications.
Pitch, Resolution & Refresh Rate
is Dot pitch
buying a new monitor, what do we need to know? A typical monitor advert
might look like-
• 15.9-inch viewing area and .25mm dot pitch
• 1600 by 1200 maximum resolution at 70 Hz refresh rate
• 119 Hz maximum refresh rate at 1024 by 768 resolution
• Three-year warranty
• Price when ranked: $239
appears we need to know about dot pitch, resolution, refresh
rate and the meaning of screen dimensions. We will also need to know
something about the difference between CRT, LCD and TFT monitors.
Resolution and Refresh Rate
pitch, maximum screen resolution and refresh rate are important factors to
consider when buying a monitor. If you buy a monitor without considering these
factors you may end up with a substandard monitor or with an unsatisfactory
display because screen resolution and refresh rate are not set appropriately.
is Dot Pitch?
monitor screen is made of of lots of tiny dots. Each dot is composed of a
triad of phosphor cells - a red phosphor, blue phosphor and green phosphor
a normal cathode ray tube monitor (CRT) an electron gun at the back of
the monitor shoots electrons at the back surface of the monitor screen.
When electrons hit the phosphor cells they glow. The colour that each type
of phosphor cell emits depends on the intensity with which electrons strike
them. The red phosphor cell can be made to glow different intensities of
red, the green phosphor cell can be made to glow different intensities of green
and the blue phosphor cell can be made to glow different intensities of blue.
set of three phosphor cells make up a dot. The colour the whole dot
appears to be depends on the intensity of the red phosphor cell, the green
phosphor cell and the blue phosphor cell. You may recall mixing paints at
school. This is similar except the three primary colours of light are red,
green and blue.
a look at this RGB Application that
shows you the colour produced when different combinations of red, blue and green
light are mixed.
try the activity~
the RGB application, what colour do you get with the following colour
= 0, Green = 0 Blue = 0
= 255, Green = 255 Blue = 255
= 255, Green = 0 Blue = 0
= 255, Green = 255 Blue = 0
= 100, Green = 100 Blue = 100
what is dot pitch?
pitch is the distance in millimeters between each phosphor triad. Dot
pitch is important because it is an indicator of image clarity and is a KEY element to consider when purchasing a monitor.
a monitor specification will give the horizontal dot pitch, sometimes
the diagonal dot pitch.
today's monitors might specify a dot pitch of between 0.22mm and 0.3mm.
The smaller the number, the finer an image can be displayed on screen. A decent monitor
should have a horizontal dot pitch of about 0.22 mm
If you know the dot pitch and size of the screen you can calculate the
maximum resolution in pixels that can be displayed.
we know what a dot is. But what is screen resolution?
resolution is the number of pixels across the screen and the number of
pixels down the screen. E.g. 800 × 600 means there are 800 pixels across
the screen and 600 pixels down the screen. But are pixels the same as
monitor specifications include maximum resolution along with dot
pitch. As an example, suppose we have a maximum resolution specified as
1600 × 1200, this means that there are 1600 dots across the screen and 1200
dots down the screen.
the graphics card can handle it, an
operating system can be configured to
consider each single dot as a pixel and can draw the desktop colouring each
pixel separately. In this case the desktop will be displayed at maximum
pixel is the same as a dot at maximum resolution only~~
although the number of dots a monitor has cannot be changed, the screen
resolution can be changed. An operating system can be configured to
consider groups of dots as pixels. As an example, suppose
the screen resolution is changed from 1600
× 1200 to 800
× 600 . This means that each
group of four dots is now considered to be a single pixel. Each set of
four dots is now coloured identically.
a pixel is a set of dots at a lower resolution than maximum~~
At maximum resolution
each pixel is the same as a dot, otherwise a pixel is a group of
the lower the screen resolution the larger the text appears. The higher
the screen resolution, the finer and smaller text appears to be. This is
because the higher the resolution, the more pixels there are.
pictures below show you two different screen resolutions.
at 1152 × 864
at 800 × 600.
how the text and image appears larger
can change your screen resolution in Windows by going to Control Panel
and double-clicking the Display icon. The
Settings tab allows you to choose the
screen resolution, the colour quality and in some cases, refresh rate.
when buying a monitor, you should note that standard
resolutions include 640 × 480, 800 × 600, 1024 × 768, 1280 × 1024, 1600
× 1200. Have a look at some of the resolutions I can set my monitor
maximum resolution you can expect from a monitor will depend on the size of
monitor you are buying and the price you are prepared to pay. Most
people today are content to set their screen resolutions to 800 × 600 or
1280 × 1024 although many people have other settings.
A 15" monitor should use a
640 x 480 or 800 x 600 resolution at least.
A 17" monitor may have a maximum resolution of
1280 x 1024, but 1024 x 768 gives a better screen ratio.
19" monitor may have a maximum resolution greater than 1280 x 1024,
but at higher resolutions it can be difficult to read text on the screen.
refresh rate of a monitor is really important. Every pixel on a screen
is redrawn many times a second. This is to maintain the quality of the
image. If flicker can be detected this will cause headaches and eye
strain. Most people recommend a refresh rate of 75Hz (each pixel is
redrawn 75 times a second.) Most monitors can be set to a higher
refresh rate than this; 85Hz is another common refresh rate.
at higher resolutions, there are more pixels to be redrawn. So if you
increase screen resolution, you may notice that the refresh rate
declines. Decreasing the refresh rate tends to allow a higher refresh
rate. Imagine a see-saw.
resolution ---- lower refresh rate
resolution ---- higher refresh rate
buying a monitor, you should always check that the refresh rate can be set to
75Hz or higher at the resolution you prefer.
specifications commonly include screen size and viewable image size. These
size is measured from one corner of a screen diagonally to the other
corner. Typically, screens come in 15", 17", 19" and
21" sizes. The greater the size the more expensive the monitor
viewable area is the diagonal distance from one corner to another of the
glass, not including the black border. This size will be smaller than
screen size. Typically a 15" monitor will have a viewable image
size of 13.9".
A few years ago 15" monitors were
common. However, after major decline in cost and advance in quality, 17" monitors
are becoming more common. Also available are 19", 21" and even 24" monitors
many years, the only choice of monitor was a cathode ray tube type (CRT.)
CRT technology is similar to a television set.
used a different screen technology - liquid crystal displays (LCD).
days you can also buy a LCD flat panel monitor for your desktop computer
monitors have the advantage of low radiation emission, compactness and
However, they are expensive compared to CRT monitors. Also, they have a
limited viewing angle. If you look at a LCD monitor from an angle then
the brightness and colour depth drops and it takes on a hazy
is because of the way light reflects off a LCD screen.
are now other alternatives to CRT and LCD monitors in the form of TFT
(thin film transistor) monitors. These are similar to LCD monitors with
similar advantages but again they are expensive and have a limited viewing
angle. LCD and TFT monitors are limited in the resolutions you can set them
to. For an optimum display it is best to leave the display settings on
the factory defaults. These monitors are not particularly suitable for gaming
or for use with CAD draughting or other graphics applications.
monitor needs to be connected to a graphics card plugged into the computer's
motherboard. The graphics card controls the operation of the monitor.
should be aware that monitor display is at the
mercy of your graphics card.
resolution you can set your monitor to will depend upon the quality of
your card. You may have a fantastic 21" monitor capable of
displaying images at 1600 × 1200 screen resolution but if the graphics card
is old you may end up with a much lower resolution setting.
inexpensive graphics cards are often capable of delivering what the monitor needs to live up to its full potential.
However, in some cases substandard monitor performance can result from old or poor quality
graphics cards. Today, AGP graphics cards tend to be chosen over PCI
graphics cards for the higher performance they can deliver.
That is folks!!