LCD Buying Guide Part 2
Brightness & Gamma
LCD's are very bright by nature. Hitachi for
example set all of their panels to 100 brightness which will
hurt your eyes very quickly if you keep the setting, you will
want to change this to somewhere around 50. Brightness of LCD's
is measured in cdm-² and the majority of panels I've looked at
all quote a figure around 250cdm-² - 260cdm-².
With full brightness controls and the fact that
at Brightness 100 the screen is too bright then there would seem
to be no harm going for a lower figure but you are unlikely to
find on. It is also debateable that going for a panel with a
higher figure will give you any benefit.
Some people have noted that games which are
rather dark do not appear too well on an LCD panel (I've mainly
heard of this issue with the Hitachi but please do not let this
put you off this great TFT). If you are having this problem you
will probably need to play with the gamma settings. A program
called PowerStrip
will help you in this field and should solve all of your
problems.
Backlight's & Backlight Leakage
Without a backlight your panel would be
extremely dull. This is what actually makes an LCD bright and is
a very necessary component. Many manufacturers actually use the
same physical panel in their displays but there are numerous
manufacturers of backlight's, some better than others.
If two TFT's are using the same LCD panel (The
Hitachi and NEC for example) and they quote different contrast
ratio's the chances are they are using different backlight's.
The backlight used to be a major fail point of TFT panels,
however like the process for making the actual panel, the
process for making backlights has improved and the reliability
is a lot higher than it used to be. The majority of TFT
manufacturers quote a backlight life of >40,000hrs. To give you
an idea that would be 4.5yrs of the panel being on 24/7 or 9yrs
with a more realistic 12/7. Because the backlight is so bright
this can cause "backlight leakage" around the sides of the
panel.
This will appear as a slight white "haze" around
the edges of a black or dark screen. Unfortunately there is no
way to totally prevent this and all TFT's will suffer from this
to some degree, however some are much worse than others.
During normal use and on bright backgrounds and
games this "haze" will not be noticeable, you really do have to
get a totally black screen before you will notice it.
Monitor "Burn-In" & LCD Fade
LCD fade is actually a myth. Some people are
under the impression that as your LCD gets older so the screen
starts to fade and the overall quality of the display gets
worse. This is not the case, an LCD will be as bright and clear
after three years as it was the first time you switched it on.
"Burn-In" is something that CRT's suffer from,
this is when you have the same image displayed on your CRT for
many hours on end. The end result is that image is burnt into
the screen and once that has happened it is there for good, this
is why it is advisable to either switch your CRT off when it is
not in use or to use a screensaver.
You maybe surprised to hear that "burn-in" is
still possible on an LCD, however the end result is not quite
the same as with a CRT. If you display the same image on your
LCD for numerous hours, once you switch the panel off or the
next day you switch it on it is possible that the last image can
be faintly seen.
With a CRT this damage is permanent however on an
LCD it is not. If you are unlucky enough to have this happen to
you simply continue to use the LCD or leave it on a screensaver
for approximately the same number of hours that you displayed
the static image - the after image will initially fade and then
vanish leaving no permanent damage to your LCD.
Can you see the "matrix"?
Because there are always a fixed number of
pixels on screen you may think that the "active matrix" is
visible and you'll actually be able to see things at a "pixel
level" rather than an overall image which you will see on a CRT.
If you sit with your nose pressed against your
new panel then maybe you would be able to start seeing the
individual pixels. However through general usage you should not
see the matrix.
The Dot Pitch on an average 17" LCD panel is
0.26mm which is extremely comparable to a CRT display.
With a 17" LCD having dimensions of 13.5"
viewable wide and 10.5" viewable height (Gives you 17" diagonal
viewable) each square inch of screen has approx. 9200 pixels in,
you aren't going to be able to make out individual pixels!
Dead Pixels
The technology behind LCD’s means that they
are quite difficult to make, even with today’s modern
technology.
Over the years the process has got better, in the days of the
early laptop TFT displays some 35% - 40% of all screens made
were “throw away” and that is what kept the prices very high.
As the technology has improved so LCD’s are less likely to fail
and the prices have dropped.
Dead sub-pixels are not uncommon on an LCD panel.
A dead sub-pixel is one that is usually stuck on one particular
colour, either red, green or blue and will remain that colour no
matter what it should be.
These pixels are most noticeable on a very dark or black
background and are less visible on a lighter one.
If is not uncommon for your brand new £375 LCD panel to have one
dead pixel and that can be very frustrating when you’ve spent
that kind of money.
You will not be able to return a panel because of one or two
“dead pixels”, most manufacturers allow for anything from 5-10
such pixels before they consider your display faulty and will
issue a replacement.
If your new panel has one or more stuck pixels the first thing
to do is to find out if they are “dead” or simply “lazy”.
First connect the display via an analogue connection and set the
display to the fastest refresh rate possible (usually 75hz).
Now get the pixels changing colour, use a screen saver, a game,
anything that gets the pixels changing colour rapidly.
What you may find was that the “dead” pixel was only “lazy” and
after 10-15 minutes of use you may well find all of your pixels
are behaving as they should be.
I’ve successfully done this on two 17” LCD panels where it
appeared they each had one dead pixel from new, after really
using the display for fifteen minutes these dead pixels vanished
and have not reappeared. Another way of potentially fixing a
stuck pixel is to gently massage the panel around the offending
sub-pixel. Hopefully after a few seconds of massaging the pixel
will pop to the correct colour and it will never reappear.
Please only use the massaging technique for only a few seconds,
too much pressure or doing it for too long could result in more
serious damage to your panel.
Dead Pixel Checks
This is a word of warning about company's who
will, for a fee, offer you a dead pixel check before your
purchase.
The system works by you paying an additional fee,
usually in the region of £30 and for that the company will unbox
your LCD, switch it on and check fro dead pixels, this way you
are guaranteed a display without any. Sounds good and it is if
you are willing to spend this extra money, however, what about
all those displays that are found to have a dead pixel?
Firstly the company cannot return them to the
manufacturer because there is not anything wrong with them.
Secondly they have stock of panels which they know have a dead
pixel or two, this stock still needs to be shifted. It doesn't
take a genius to work this one out, only buy from a company that
offers a dead pixel check if you are willing to pay this fee.
Buying from such a company and not paying this
extra all but guarantees you will get one of the panels found to
have at least one.
ClearType
There are those people who like "Clear Type"
and those that are not too keen. This is actually Microsoft's
way of smoothing icons and the like under Windows and is
designed to be used whilst using an LCD display. To activate
this feature under Windows XP you will want to go to the
following location:
Display Properties>Appearance>Effects now in
the second of the two drop-down menu's select "ClearType". All I
can suggest is that you experiment with this setting and see if
you like it or not.
You've made your purchase; you've taken delivery, what now?
So you've decided to make a purchase and you
are now the proud owner of an LCD panel. What should you do
first?
You really need to test this LCD now and make sure you are going
to get on with it. Looking at an LCD can be a rather strange
experience to start with, the screen will look different and
I've spoken to people who after an initial look decide they
simply don't like it. Don't give up after that first view, you
do need to give it a little time.
You really should start by using the applications & games that
you use on a normal day. It's all well and good being impressed
with the image quality on a game you fire up once a month, but
how it looks with a game you play daily is far more important to
you. The same goes for general everyday applications like
Internet Explorer or Microsoft Word, use these applications and
see how you are going to get on with the display.
To give your display the once over and also to check for
dead/stuck pixels a really handy online LCD Toolkit can be
located
here.
Don't give up on the panel after only one use, on the flip-side
also don't assume it is perfect for you the first time you power
it up - give it a little time, start running some applications
and games on it and then decide.
Guide Parts
1 2
3
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