LCD Buying Guide Part 1
More and more people are now interested in
buying an LCD panel for their computer.
LCD's are not for everyone, the discerning
hardcore gamer will probably want to stay with a CRT for the
time being, however even those people who play a lot of games
may well see the advantages of an LCD far out-weight the
disadvantages.
Below you will find a guide on what to look
for in an LCD panel, I hope it is of use to some people.
Screen Size
Unlike with CRT monitors, with an LCD the
diagonal size indicated is the visible viewing space.
So a 17” LCD will measure 17” from corner to corner.
A 17” CRT can measure as little as 15” from opposite corners.
So for approx CRT to LCD relative sizes you should consider the
following:
17” CRT – 15” LCD
19” CRT – 17”-18.4” LCD
21” CRT – 19”-20” LCD
Please note these are just approximate sizes. A 19" CRT that
gives you 18" of viewable space is of course going to be larger
than a 17" LCD panel.
Resolution
All LCD’s have an optimum viewing resolution,
this is due to the fixed number of pixels the panel has.
Due to this you can obviously never go above the maximum
resolution setting of your panel.
You can run an LCD in a resolution lower than the optimum
setting; however as a rule quality will suffer.
The further you move away from the optimum resolution setting
the worse the overall image quality will be.
An LCD will happily scale to any resolution you decide to run,
however as you drop resolution more physical pixels are used to
represent a single pixel on a screen draw - for example, when
running a 17" LCD at 1024x768 you may find that every "single
pixel" an application asks to be drawn, four "physical pixels"
are used by the LCD. Because pixels are so small this is not too
noticeable, however drop to 800x600 and things start to look
worse.
Usual optimum resolutions for LCD panels:
15” LCD – 1024x768
17”-18.4” LCD – 1280x1024
19” LCD – 1280x1024 - 1600x1200
20” LCD – 1600x1200
With this in mind you should consider matching your LCD to your
graphics card. If you purchase a 17” LCD and have a graphics
card that really cannot cope with games at 1280x1024 then you
are going to be scaling all of your games which will reduce
overall image quality and increase the chances of streaking and
ghosting. Saying that your LCD is going to be an investment, buy
a 15" LCD now and in a year you may well have the graphics
hardware to run your games at 1280x1024 but due to the
limitation of the 15" LCD you will not be able to.
Due to the fixed number of pixels on an LCD screen the "maximum
resolution" means just that, you cannot go any higher due to a
lack of physical pixels.
As an example here are the number of physical pixels your panel
will have depending on its maximum resolution:
1024x768 - Approx. 786,000
1280x1024 - Approx. 1,310,000
1600x1200 - Approx. 1,920,000
So as you can see, if your "maximum resolution" is 1280x1024 you
are approx. 610,000 pixels short of the 1600x1200 resolution.
Refresh Rate
The first thing you need to know is that LCD’s
do not flicker like CRT’s at low refresh rates.
In fact all LCD manufacturers will tell you that the optimum
refresh rate for their LCD panels is 60hz (a figure that would
give you a headache within minutes on a CRT).
Most LCD’s will support refresh rates up to 75hz when using an
analogue connection although looking at a panel running at 60hz
and one running at 75hz next to each other you would not be able
to tell the difference.
When looking for an LCD panel the refresh rate is not something
that should concern you. The panel will have an optimum refresh
rate and no matter how low that may appear when compared to a
CRT your panel will not flicker. This can be difficult to
comprehend, especially if you have been using a CRT for many
years and have been told again and again that 60hz will hurt
your eyes, trust me on this one, 60hz on an LCD will be rock
solid and great on your eyes.
Response Rate
The response rate is made up of two figures
“Rise” & “Fall” (-tr & +tf).
These two figures added together will give you the total
response rate of your LCD panel.
This total will range from 16ms (the fastest currently
available) right up to 50ms (the very slowest LCD displays).
Ideally you want a panel with a lower response rate as possible,
the lower the response rate the quicker each individual pixel
can move from white to black (or vice versa) and the quicker the
screen can be re-drawn.
Tests by many people indicate that if you wish to play games or
use other fast moving images on your panel (such as DVD’s) you
should be looking at a maximum of 30ms - that is the maximum you
should consider, others will tell you that 25ms is really the
slowest you should consider.
The higher the response time the more likely your display will
be subject to “ghosting” and/or “streaking”.
This should not necessarily be the single most important factor
in the purchase of an LCD panel, but should feature as one of
the most important, especially if you are a gamer – a hardcore
gamer really should be looking for something <25ms.
Note: When looking at LCD panels read the full technical
specification and not the “general features” page.
Some manufacturers will quote a low response rate, however they
are only quoting the “tr” time and you still need to add the
“tf” time to get the total response time – I’ve seen a display
at 25ms become 40ms once you read the full specification.
16ms Vs 20ms
At the current time the very fastest panels on
the market have a 16ms total response rate.
All 16ms LCD's use the same physical panel, one
made by AU Optronics. As it turns out 16ms and 20ms panels are a
lot closer in performance than maybe you would think.
The 16ms panels initially display colours from a
252k colour palette. Should a colour be required outside of this
palette two colours are shown in quick succession, so all 15.2
million colours (True Colour) can be displayed however response
rate suffers.
If a 16ms response rate panel needs to display a
colour outside of its initial palette expect the response rate
to drop to around 20ms.
If is important to note that all response rates
quoted are "typical". Sometimes the colour change maybe faster
and other times it will be slower. However it is still safe to
say that anything with a 16ms/20ms total response rate will show
no ghosting/streaking.
Colour Depth
The majority of LCD panels display from a
palette of 15.2 million colours (true colour).
However those panels which have a response rate of 16ms use a
slightly different system as detailed in the above section.
The system of showing two alternate colours to
give you the full range of "true colour" does work very well,
there is no noticeable flickering on screen because of the two
colours being shown.
It is widely accepted however that if you demand
100% accurate colour matching then you maybe better of sticking
with a CRT for the time being.
Contrast Ratio
The contrast ratio is the difference in light
intensity between the brightest white and the darkest black. A
higher contrast ratio represents a better colour representation
(the better information will appear against a dark background)
than on an LCD with a lower contrast ratio.
Basically speaking the higher the contrast ratio the stronger
colours will look, the better the detail will appear.
LCD panels will range from 200:1 to 700:1 with the average
around 350:1 – 500:1
When considering an LCD panel a contrast ratio of at least 350:1
possibly 400:1 should be the minimum considered.
Viewing Angles
This is another area where TFT's have moved on
leaps and bounds. It used to be the case that you needed to sit
directly in front of an LCD to actually see the image clearly,
even the slightest deviation over to one side or another would
result in the image fading and you not being able to see
anything.
I personally do not feel that the viewing angle
is of major importance when purchasing an LCD panel. As the user
of the computer you tend to sit in front of the panel or ever so
slightly to one side and all modern LCD's can cope with this
without a problem.
Viewing angles are measured in degrees Horizontal
& Vertical. Although some high figures are quoted you will still
get the best possible image quality and colour clarity if you
sit dead-central on the panel. The average viewing angle on
modern LCD's is approx. 160°H x 160°V giving you a wide viewing
angle for those times more than one person needs to look at the
screen.
Analogue (D-Sub) Vs Digital (DVI)
All LCD panels will offer an analogue
connection with the majority of them now also offering a digital
port too.
To use this digital port your video card must also have a DVI
port on.
You will also need a special DVI cable to run between the video
card and LCD panel, some LCD’s ship with this cable others do
not. It is worth noting that a good quality DVI cable can cost
anything from £25 to £50 so if the panel you are looking at does
not ship with such a cable you need to take this into
consideration when working to a budget.
A true digital connection should improve image quality and the
general “sharpness” of the screen.
The difference is not night & day but to those people with a
keen eye it should be noticeable.
It is also worth noting that when using the D-Sub connection you
are going through a couple of conversions, digital to analogue
and then further down the line analogue back to digital.
With DVI you are using a true digital connection from one end of
the connection to the other.
Choosing the right DVI cable
Not all DVI cables are the same. If your LCD
ships with a DVI cable then obviously use this one, the
manufacturer will have made sure it is up to the task. However
if your LCD does not come with a DVI cable you need to make sure
you get one that can support the resolution you are likely to be
running at.
If you purchase a 17" LCD make sure that the DVI
cable you purchase is NOT designed for a 15" LCD. They will look
identical, however a cheaper DVI cable will not actually provide
the correct bandwidth needed for your higher resolution, this
will result in very bad picture quality and the image will also
shake.
If anything buy a cable that guarantees more
bandwidth than you require and if the cable is less than £10
(UK) then be wary.
Belkin make
excellent quality cables and I highly recommend them for all of
your cable needs, not only DVI cables.
The two cables that will be suitable for 99%
of LCD panels are listed below. The single link cable is fine
for the majority of people and provides more than enough
bandwidth for panels running at 1600x1200. The dual-link cable
will of course give you bandwidth above and beyond what you need
for now but give you a little more "future proof".
Belkin DVI Single-Link (F2E4141x10-SD)
Belkin DVI Dual-Link (F2E4141b10-DD)
Guide Parts 1
2
3
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