Is the iPAQ h1940’s display really yellow?

by Reads (35,283)

iPAQ h1940 Pocket PC One of the most important elements of a handheld is its display. While there’s no doubt that handheld displays have improved dramatically over the past three years, consumers have also become increasingly more demanding. They’ve begun to notice subtle differences in screen brightness and color reproduction, and sometimes they don’t like what they see. Take the case of the new iPAQ h1940 Pocket PC from Hewlett-Packard.

Its predecessor, the iPAQ h1910 Pocket PC, gained a reputation as having one of the best color screens found on a handheld device. Unfortunately, the h1910 lacked a couple of other key features — such as integrated Bluetooth wireless technology and an SDIO slot to accommodate advanced accessory cards — so it fell short of assuming the status of “the perfect PDA.” Then along came the h1940. Complete with Bluetooth, SDIO and more memory than before — all at under $300 — it appeared to be the handheld everyone had been waiting for. But then something odd happened. Initial purchasers of the h1940 began to complain that the display exhibited a yellowish cast. Suddenly the “perfect PDA” had a flaw, and one that to some wasn’t easily overlooked.

What Brighthand has discovered is that indeed at certain viewing angles the white elements on the iPAQ h1940’s screen take on a yellowish hue. It’s a condition called grayscale inversion and it’s caused by the optical anisotropy of the obliquely aligned components. In other words, light reflected at different angles can appear as different colors to the human eye. So when you change the angle at which you’re viewing your handheld’s LCD, the light is reflected off of the liquid crystal cells at a different angle and with a different intensity. There’s also the possibility that HP chose a less expensive LCD that uses yellow-green LEDs to light the screen rather than more expensive white LEDs, and different viewing angles can cause “light leakage” from the yellow-green LEDs.

LCD manufacturers are keenly aware of the viewing angle issue and have been compensating for it by using specially-coated optical films and new types of liquid crystal cells, such as IPS-mode and VA-mode cells. But these solutions have generally concentrated on improving the horizontal viewing angle more than the vertical viewing angle. That’s because a person viewing an LCD connected to their desktop computer or laptop is more likely to shift side-to-side than up and down. However, with a handheld computer that’s not necessarily the case.

Rather than sitting on a desk, handhelds are held in the hand, which naturally tends to Tilt them up-and-down rather than side-to-side. With the iPAQ h1940, its display produces very little gray-scale inversion when turned slightly left or slightly right, or side-to-side. However, tilt it downward and the screen darkens (you may even notice some ghosting, where dark images lighten and light images darken, in some areas of the screen). Tilt it upward and it becomes lighter and yellower.

Is there a reason that HP didn’t use the same screen used in the iPAQ h1910? Probably, and it could be for any of a number of reasons. Since HP added Bluetooth, SDIO and additional memory and offered it at the same price as the h1910, it may have been pressed to reduce costs in other areas, such as the display and processor. Or it may have just made a wise business decision to utilize multiple LCD manufacturers to ensure adequate quantities at competitive prices. Whatever the reason, it’s an issue that consumers must take into account when deciding whether to purchase the iPAQ h1940 or not.

What can current iPAQ h1940 owners do about this issue? Well, there are basically two courses of action. One is to view your handheld head on rather than at angles. This eliminates grayscale inversion, producing acceptable whites with little or no yellowing. The other alternative is to return the device and buy the $399 iPAQ h2210, which does not suffer from this problem.



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