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Compaq 1520D

It is a mainstream model from Compaq, which is now merged with HP. It has rather average specifications according to today’s standards: 120/100 degrees viewing angles (along the horizontal and vertical, respectively); 35ms response time; 250nit brightness (1 nit = 1 candela per square meter) and 350:1 contrast ratio. Nevertheless, we didn’t reveal any inconveniences at work: the effective viewing angle allows reading text on the screen even looking in parallel to the matrix, although colors become yellowish at a more than 45 degree deviation from the direct view. After brightness and contrast were set to 40-50% of the maximum, it was possible to work in a brightly lit room. Controls are quite handy, too: large and easy-to-press buttons, a clear menu system… The display has two outputs – VGA (D-Sub 15) and DVI, which is a rare feature among 15” models.

The display base allows turning it to portrait, which is quite useful when working with documents (historically, the orientation of pages is portrait) or in the Internet (many sites are intended for 800x600 resolution and at higher resolutions there is a broad blank margin on the right). On the other hand, the height of the base cannot be adjusted, and the power supply unit is external, which is not always handy.

During the tests, this display showed 32ms pixel light-up time and 7ms pixel fadeout time – overall, we have 39ms response time. It is a little above the specified 35 milliseconds.


Light-up time


Fadeout time

Iiyama BX3814UT

This display doesn’t boast any extraordinary features, as well. Its specifications are just a little better than those of the Compaq model: 120/100 degrees viewing angles, 30ms response time, 320nit brightness, 300:1 contrast ratio. The viewing angles turned to be rather strange: the manual said you could look at the screen at an angle of 40 degrees from above and 60 degrees – from below. In practice, however, when you looked at the display just a little from below, its upper part got noticeably darker. At the same time, it’s all right when you look at it from a side or from above, and the picture is quite discernable even when your line of view is in parallel to the screen. Subjectively, the eyes were least of all tired when brightness and contrast were set to 40%.

The design of the model is a bit clumsy and bulky, especially that broad bezel. The base has no height-adjustment options; the portrait mode and wall mounting (a useful thing sometimes) are not available, either. Although this model has rather large dimensions, its power unit is external.

The menu is far from perfection. It’s too ascetic, although there are all necessary functions present. The most common settings – brightness, contrast and self-tuning – are accessed with one button, though.

This display also proved a little worse than its specs said: 35ms (28ms pixel light-up time and 7ms pixel fadeout time).


Pixel light-up time


Pixel fadeout time

There is one more interesting thing about this display: the backlight lamp is modulated. To control brightness, the manufacturer used a width-pulse modulation of the lamp power supply (as you know, LCD displays use fluorescent lamps with high-frequency power supply, about 40…60kHz) with a frequency of about 260Hz. This was quite clear in the oscillograms, taken at a low brightness level (when brightness is high, the impulse width gets larger and independent impulses practically converge into one):

Of course, the eye cannot discern such frequencies, so all the things mentioned above are nothing more but just a curious fact.

 
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