tutorial
STAY AWAY FROM XGA!
By Abrie du Plooy (Electrosonic SA’s NEC and GALAXY Product Manager)
Why you should think twice before
investing in XGA projector technology.
Today’s marketplace offers various viable audiovisual solutions catering specific and general
requirements. Different technologies, features,
warrantees and many more attributes make it
all the more difficult to purchase the correct
product. It offers a Smartie box full of colours to
produce a canvas that sometimes only requires
black and white.
ratio to emphasize this. However, HD standards
stuck to 16:9. Computer manufacturers took
the commercial side to this a tad further and
developed a 16:10 display which is mostly
available in 1280x800 and 1920x1200 – both of
these are HD.
Options are great to have, as long as one is well
informed as to which are key and which aren’t
when designing a solution. When it comes
to projectors, and especially high-brightness
installation projectors, decisions are often
mistakenly based on ANSI Lumens and the depth
of one’s pocket. As a result, an important feature
such as resolution is easily overlooked.
The comparison between two aspect ratios
Resolution is very important in current projection
and video technology. Not only does it define
image quality in line with current High Definition
(HD) standards, but also determines screen
shapes.
Screen ratios pertain to old or new technologies.
In earlier days, the standard ratio of screens was
4:3 - almost square in shape. Lately with HD
standards, images are ‘Wide Screen’, with a 16:9
or 16:10 screen ratio. These images appear as a
more rectangular shape.
Aspect Ratio:
The ‘Aspect Ratio’ of a display refers to the width
and height of said display. The first digit indicates
the width in unspecified units and the second
digit then resembles the height in a number of
equal units. Standard Definition was broadcast in
a 4:3 screen ratio – an image that is 4 units wide
and 3 units high. Previously Standard Definition
was all that was available. PAL TV (768x576) was
the broadcast video standard and computer
displays had VGA (640x480), SVGA (800x600) and
XGA (1024x768) resolutions.
Even though there are many more resolution
standards, these were all 4:3 aspect ratios
and thus selecting a correct aspect ratio
wasn’t a challenge. More recently, television
manufacturers produced ‘Wide Screen’ displays
with many different resolutions – some quite
strange. Most were experimental and not relevant
in the long run, but nonetheless, ‘Wide Screen’
television was introduced … and it was sexy!
When consumer video quality elevated to HD, the
entire picture changed – literally. Displays were
produced in 1366x768 formats as 16:9 aspect ratio
was the HD standard. The ‘HD Ready’ resolution
offered 1280x720 (also known as 720p). This was
soon followed by ‘Full HD’ displays which offered
1920x1080 (known as 1080p or 1080i). The big
difference with HD however, was the shape of the
display.
The ‘Wide Screen’ standard was liked and accepted
everywhere as it is a truer approximation of
human vision. With two eyes next to each other,
our natural view is wider than it is high. Certain
directors shoot their movies in a 21:9 screen
quality is reduced by about 45%.
So Why Not XGA?
Scan Converting (Down-Scaling)
If a ‘Full HD’ camera sends an image (with a
width of 1920 pixels) to an XGA projector, then
the image needs to be compressed to fit into the
1024 available pixels. The XGA projector simply
cannot display an image wider than that. In order
to retain the right shape, the same then applies
to the height which is also compressed to stay in
relation to the width. As a result of this, the initial
‘Full HD’ image is reduced to a mere 1024x576,
which is below even ‘HD Ready’ standard
(1280x720). Thus, the very expensive ‘Full HD’
camera with 2 Mega Pixel capture (1920x1080)
only displays 54% of its original image. The big
investment into HD source equipment is being
flushed down the drain by using the wrong
projector.
The result when the wrong aspect ratio is used
Which Technology to choose?
The answer to this is easy. By maintaining
current technology levels you will automatically
future-proof the installation and also avoid
disappointment. Acquire a projector that can
support HD and all presentations should be
problem-free. In some cases you might need to
stick to XGA, just make sure that it meets your
particular requirements. Among the HD options
there are a further 2 choices, ie. 16:9 or 16:10? The
16:9 Aspect Ratio is more often focussed on video
images where 16:10 is more common for data
projections such as documents or spreadsheets.
Pricing, Resolution and Brightness
HD projectors can be expensive. Projector cost
is inflated more by the resolution than by the
brightness. High brightness units with low
resolution could seem very attractively priced,
but you could be fooling yourself. Make sure that
a more affordable unit doesn’t claim its price with
a lower quality image.
The projector offering from NEC only
offers 4 different resolutions:
•
•
•
•
XGA 1024x768 (4:3)
WXGA 1280x800 (16:10)
‘FULL HD’ 1920x1080 (16:9)
WUXGA 1920x1200 (16:10)
With these resolutions available, different
brightness levels are offered from 2500 ANSI
Lumens all the way up to 13 500 ANSI Lumens. In
industries where high brightness projectors are
required, the cost of these could easily spiral out
of control. Certain manufacturers promote high
brightness projectors at a relatively good price
without mentioning that its native resolution is
only XGA.
They would assure you that it is capable of
accepting ‘Full HD’ signals. Everything will seem
A–OK until you send a ‘Full HD’ image to the
projector and only then realize that the image
24 PROMAG – second quarter 2014
In the above diagrams one can clearly see the yellow ‘Full HD’ image
being compressed to fit into the white XGA image.
FAQs
But XGA is much cheaper and sometimes
equally bright?
Yes it is, and it will be. Because the resolution is
lower than HD and because it’s old technology, it
will be substantially less expensive than current
technologie ˂