18September

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 audio-visual 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. 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.

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 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.

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 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. It is even below ‘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.

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 technologies.

But it’s ‘Full HD’ compatible?
Yes it is. In fact, it has to be in order to survive amongst current competitive technologies. It is able to accept HD, but it cannot display HD resolution.

But the horizontal 768 lines can accommodate ‘HD Ready’ (720p)?
Yes it can, but the 1024 width is narrower than the 1280 width of a 720p signal. So the picture will be compressed in width and in height until it fits.

All in all, one needs to keep the entire display chain the same. If one starts off with HD video, it is important to ensure that all cables and equipment in the distribution and display thereof, are HD-rated. This is necessary to deliver and display the HD image at the end.

For advice on projector and screen selection, please feel free to contact This email address is being protected from spambots. You need JavaScript enabled to view it..

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