Viewable Image Size vs Screen size

Many customers look at flat panel displays and feel that the images look bigger than they do on the same size CRT monitors. In fact, they look bigger because they are bigger. CRT monitors are measured by their bezel sizes, such as 17", 19", or 21". But a CRT monitor's viewable image size is smaller than its bezel size. This is why CRTs list their viewable image area in addition to their bezel size. For example, a 17" CRT monitor usually has a 15.6"-16" viewable image area. By contrast, the new flat panel displays are rated by their viewable image size only, a 15" flat panel display has a 15" viewable image area.

Hitachi S-IPS Technology Overview

Conventional TFT displays begin by using twisted liquid crystal pixels. When electricity is applied to these pixels, they straighten. Most of them provide images perpendicular to the screen, and some shoot off at angles to provide viewing angles of 90 - 120 degrees.

These displays vary in color, clarity, and contrast. If you think of the pixels as short cylinders, in conventional TFT the light you see is being emitted from the ends of the cylinders. The long sides of the cylinders, which emit most of the light, are facing the side walls – making the image lose much of its viewing angle. The drawing below illustrates this concept.

Hitachi combats this problem in both of its flat panel technologies. Hitachi's patented STFT technology not only places the pixels parallel to the glass, it also spins the pixels (think of the disco balls of the 70s) so that equal light, image, color and clarity are delivered to all areas of the screen. This is what provides the super-clear, wide viewing angles that Hitachi panels are famous for.

Now Hitachi has upgraded its award winning STFT technology to S-IPS by employing a new electrode structure to drive the liquid crystal molecules. Hitachi's S-IPS technology now employees a "zig-zag" electrode structure to improve images and reduce color shift. This zig-zag structure arranges the molecules to compensate for color shifts at certain angles (where whites can turn blueish or yellowish). By angling the orientation and arranging the color shifts to compensate for each other, Hitachi achieves high contrast images with extremely low color shift regardless of the viewing angle. 

The first diagram (electrode schematic) below shows the new zig zag structure and how the alternating angles on the left compensate for the color shifts (represented by the dotted arrows) on the diagram to the right.

The second diagram below (color chromaticity) shows the reduced color variance of Hitachi's S-IPS Technology. The thin lines on the right diagram show the broad range of color variance for an average conventional TFT display and how it compares to IPS technology (the color swatches). In the left diagram, you can see that Hitachi has further improved its color uniformity with the new S-IPS technology. Color variance is now in a tighter grouping showing a further increase in color uniformity.

Image Resolution and Refresh Rate

Flat panel displays are all set up like a grid. Unlike CRTs, which have 1800 or more physical pixels, virtually all 14" and 15" panels are 1024 physical pixels wide and 768 pixels high. This is why all vendors of flat panel displays suggest using the 1024 x 768 resolution exclusively for 14" and 15" panels. By the same token, the best resolution for 18" panels is 1280 x 1024, because of their physical size. Using a lower resolution such as 800 x 600 reduces the physical pixels to the center 800 x 600 pixels in the middle of the display; making the viewing area significantly smaller or using a smoothing algorithm to strectch the image, degrading clarity.

The expand function is like using the zoom enlargement function on a copier. It displays images at full screen size. The expand function causes a loss of definition, which is inadvisable, especially when using text. While some people find this picture acceptable, in all current flat panels it does degrade the image and is not recommended by most vendors, including Hitachi, for extended use.

You will also notice that, unlike CRTs, most vendors recommend using a lower refresh rate ; 60 or 70 Hz; if this setting can provide an acceptable picture with your application. For example, the LC153 will run at 1024 x 768 with a 75Hz refresh rate. However, the picture sometimes looks better at 60Hz, depending upon the application. This is true with all flat panels, and other vendors also suggest using lower settings, which can sometimes attain better pictures and text than higher refresh rates. The reason for lower refresh rates in LCDs is because the liquid crystal molecules damper flicker and higher refresh rates are not as important. So you can choose a refresh rate that looks best with your application.

Brightness and Contrast

Flat panel displays are significantly brighter, and feature higher contrast, than traditional CRTs. For example, the average 17" monitor features a brightness of 90 - 130 cd/M2 (candelas per square meter, or nits), while flat panel displays feature brightness ratings of 200 - 300 nits.

There are also significant differences in contrast ratios. CRTs feature contrast ratios around 190:1 to 245:1, while flat panels have contrast ratios from 200:1 to 500:1.

So, while flat panel displays in general feature higher brightness and contrast than similarly sized CRTs, Hitachi's flat panel displays feature significantly higher brightness and contrast than the average flat panel display.

Reduced Glare and Eyestrain

One of the benefits of flat panel displays is reduced glare and eyestrain. Because of the liquid crystal panel screen, these displays can be placed facing a window and still provide comfortable viewing. The difference between flat panels and CRTs in this area is amazing — especially if your work area is by a sunny window.

Enhanced Text Display

Hitachi's patented, STFT and S-IPS technology provides some of the sharpest, clearest text available. Images are stable and easy on the eyes, without any of the fading or blurring found in many panels. Hitachi uses a performance-enhance function to improve text quality at all resolutions by outlining the pixels used to create letters with an additional thin-line, gray scale smoothing algorithm. The panel uses data and intelligent chips on the glass to calculate the gray scale level for each new pixel and provide a smoothing effect, as illustrated here.

Space-Saving and Environmental Benefits

Hitachi flat panel displays offer a whole new world of convenience and energy savings.

Incredibly thin, with panel depths of 1.5-3 inches (panel only) and a 7" average depth including the base- these panels are light enough to move and carry. In fact, they are so light that some customers even use these panels rather than a projector for small client meetings!

Most panels are approximately 7-8" deep. Compare that to the average depth of a 17" monitor that is usually around 17" – 17.5" deep. Not only does this save space on your desktop, but most panels can even be mounted on a flexible wall mount or desktop-mounting arm, so they can be moved to any angle. You can buy these mounting pieces separately from vendors that specialize in these products (www.ergotron.com, www.premiermounts.com or www.LCDarms.com to name a few).

Because of their liquid crystal medium, flat panel displays emit no magnetic and very low emission fields — significantly less than CRT monitors. In addition, all Hitachi flat panel displays are TCO certified — they are built and tested to TCO 1995 or 1999 specifications, which are the strictest European specifications for ergonomics, emissions, energy savings, and ecology.

Hitachi flat panel displays on average use less than 1/2 to 2/3 of the energy to operate than the average CRT. For companies that run hundreds of monitors every business day, cutting monitor power requirements by two-thirds represents a significant savings in electricity costs.

Why a CRT May Still Suit Your Needs

While flat panel displays are amazing and offer numerous benefits, CRTs are still the best choice for some consumers. People who need to work with multiple resolutions — especially 1600 x 1200 and higher — are better off with CRTs because flat panels cannot support very high resolutions, and will show degraded images at non-prime resolutions.

In addition, CRTs are significantly less expensive than flat panel displays, so if budget is an issue, you can get larger screens on CRTs for the same money as a smaller flat panel.

There is no doubt that flat panels are the wave of the future and have a host of great benefits, from space savings to improved brightness and reduced glare, but there are still some cases where CRTs are a better fit.

If you are unsure which technology is best suited for your needs, please contact a Hitachi pre-sales support representative at 1-800-441-4832, and they will be happy to discuss your questions and evaluate your requirements to help you choose the right display.