As we can see in the example above, the "old" 32-inch TV has 491.52 square inches of screen area, and the 32-inch HDTV has 439.6 square inches — in other words, less. When comparing an "old" TV and HDTV of the same diagonal screen size, the HDTV screen is actually 11 percent smaller. This is true whether comparing 32-, 42, 50- or 60-inch screens: A 60-inch HDTV screen is 11 percent smaller than your old 60-inch non-HD projection screen. To make sure

your HDTV has the same screen area as your old TV, it needs to have a diagonal measure ("screen size") that’s six percent bigger. (Why not 11 percent? The math involves logarithms and square roots — i.e. Pythagorean geometry, not simple multiplication. Trust us on this.) In other words take the diagonal screen size of the old TV and multiply by 1.06. If you have a 32-inch regular TV, this means the HDTV needs a 34-inch screen if you don’t want your new TV picture to be smaller than the old one (32 times 1.06 equals 34). But this is not the whole story, especially when it comes to watching "old" TV shows on your new HDTV. Read on . . .

The “Seinfeld” Factor

A better yardstick (so to speak) than screen area is screen height. If your new HDTV has a screen that’s as tall as your old one, not only will you be sure that you’re getting a bigger picture, you’ll also be certain that when you watch "old," non-HD programs on your HDTV, the picture you’re looking at will not be drastically smaller than the one on your old TV set.

BACKGROUND: We’re all familiar with "letterboxed" TV -- bands across the top and bottom of the screen when we’re watching a widescreen movie on regular TV, for instance. When that situation is reversed — when we’re watching a "narrowscreen" program on HDTV — there are bands to the left and right of the picture. In other words, if we are watching anything from I Love Lucy to Seinfeld, or home videos, the pictures look like this:

AS YOU CAN SEE from the two 32-inch TVs above (the same TVs shown at the top of the page), watching "regular TV" on an HDTV with the same diagonal screen size as your old TV gives you a picture that’s 33 percent smaller — only about two-thirds as big as on your old set! To avoid this pitfall, use this rule of thumb: Make sure your HDTV has a screen that’

the same height as your old TV screen. To do this without taking a tape measure to Best Buy, you can either do the math yourself, or use our handy chart below. It’s based on this simple rule: To find the HDTV screen size (diagonal measure) that gives the same height as your old television, take the screen size of the old TV and multiply by 1.22. So if you want an HDTV with a screen that’s the same height as your old 34-inch TV, for example, the chart below shows that you need to buy an HDTV with a 42-inch screen, and that they will both have a height of 20.4 inches. On either TV, a non-HD picture will be the same size. The total HDTV picture area will be one-third greater than the total picture area of the old set.

Old Screen Size (Diag., Inches) Screen Height HDTV Screen Size (Diag.) 21 12.6 26 27 16.2 33 29 17.4 35 31 18.6 38 32 19.2 39 34 20.4 42 36 21.6 44 40 24.0 49 42 25.2 51 50 30.0 61 55 33.0 67 60 36.0 73

Above: If your old TV has a 34-inch screen, for older programs like I Love Lucy, Seinfeld etc. to be the SAME SIZE on your new HDTV, the new TV should have a 42-inch screen.

Xerox plans the future of today

Xerox’s Parc research lab is a shrine to innovation

A rare glimpse of the future has been given by Xerox at its famed Palo Alto Research Centre (Xerox Parc).

On show were a handful of innovations including re-usable paper, environmentally friendly plastic, solar power, water filtering and a cell detection method that could help save lives.

"I think it is extremely critical to continuously come up with innovative ideas and work with your partners to turn them into innovations that the customers of the world can benefit from.

"If you stand still you become obsolete."

Xerox along with commercial partners, universities and the government spends $1.5bn (£754m) on research and development at Parc and other research centres around the world.

Ms Vandebroek said this was just the tip of the iceberg and that she found it hard to choose just one project as a favourite to show journalists.

"It’s like picking between your children," she said.

"We picked 10 out of many more projects that are happening in the world today. The ones we have chosen today are among the newest, that are important to our customers and critical to the future of Xerox and they really enable a sustainable world. So that is really what Xerox and Parc is all about."

Parc is something of a shrine to innovation. Over the years it has given us ethernet, laser printing and pioneered the idea of ubiquitous computing. Today Xerox is hoping some of these innovations will have just as great an impact on our world and its bank balance.

1) Rare Cell Detection 2) Erasable paper 3) Panel plans

4) Spiral cleaning 5) Greener plastic 6) 3D print preview

RARE CELL DETECTION

Laser light is helping boost the chances of spotting cancerous cells

In America 1500 women every year miscarry after undergoing amniocentesis - a test that tries to spot genetic abnormalities in a child while still in the womb.

In the next two to four years scientists at Parc, along with colleagues at the Scripps Research Institute, believe they could replace amniocentesis with a simple blood test given when a foetus is between 8 to 12 weeks old.

Dr Richard Bruce said the ability to locate rare blood cells was done by combining laser techniques with a bundle of optical fibres that can accurately find circulating tumour cells and examine them with a high resolution digital microscope.

Their Fiber Array Scanning Technology is 1,000 times faster than digital microscopy, the current gold standard.

Dr Bruce labels blood with tiny markers and runs a laser over them to give off a fluorescent light. The different colours given off reveal what types of cancer is lurking in the blood.

"This has the potential to be ground breaking and more importantly save lives."

Dr Bruce has also been using the technique to detect breast and lung cancer.

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ERASABLE PAPER

Light is used to print on Xerox’s erasable paper

Although Xerox is a company largely built around printing and copying, some of its researchers are looking at ways to help people use less paper.

Researchers Paul Smith and Eric Shrader had green thoughts in mind when they came up with the idea of paper that erases itself completely after 24 hours.

Xerox research suggests that upwards of 40% of printed documents are used only once.

It’s estimated that 15.2 trillion pages of paper are printed worldwide and Xerox predicts the figure will grow by 30% in the next 10 years.

Said Mr Shrader: "The problem is getting a lot worse and its simply because people love paper."

Erasable paper is coated with photosensitive chemicals that turn dark when hit with a UV light.

The printer that goes hand in hand with it does not use toner or ink - instead light prints the images.

Mr Shrader said that after 24 hours whatever was printed on the paper disappears. the paper can be reused up to 100 times.