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End user discomfort by correcting video settings

You can end user headaches and eyestrain with correct video settings. But how you go about correcting the settings depends upon the hardware involved. This Daily Drill Down from Scott Lowe can help you sort through some of your options.


Video card and monitor settings can be the biggest factors in eyestrain and headache discomfort for your users, who spend long periods at a computer. I will explain in detail how the video adapter and monitor settings affect the user's monitor display and how they can be adjusted for more comfort. In addition, I will explain the affect refresh rate and dot pitch have on display settings.

The terminology
A number of terms describe how video settings affect the screen display, and in many cases, more than one word or phrase can refer to the same thing. I’m going to attempt to clear this up in Table A below:

Table A
Common video settings terminology


Factors affecting display
In essence, all of the settings explained above come together to produce what a user sees on the screen. When looking at a particular display, what a user sees is defined by the screen area or resolution. The refresh rate determines how much flicker the user will see on the display, and the number of bits per pixel assigned to keep track of the pixel color value determines the color depth. The number of bits per pixel is dependent on the resolution and how much video memory is on the video adapter. The greater the number of bits assigned, the greater the number of available colors and the sharper an image will be. However, more bits require more video RAM, illustrated in Table B below.

Table B


You may ask why there are video adapters with 16, 32, and even 64 MB of RAM if an adapter only requires 8 MB to get to 1,600 x 1,200 resolution. Some video adapters and monitors support much higher resolutions, and many have 3D capabilities, which require additional bits of memory in order to support their advanced features.

It’s important to run a video system at a resolution that is conducive to the work being performed. For example, when working on a single Microsoft Word document, almost any resolution will do, but when creating high-quality graphics or producing a video, a user may require a video resolution that is much higher than 640 x 480. Users with higher video resolution needs will require video adapters with more RAM and good quality monitors that can support refresh rates above 75Hz. Providing these users with an appropriate resolution is important and will almost certainly increase their productivity.

The refresh rate and how it relates to user comfort
Now let's take a look at what causes the screen to flicker, thus causing eyestrain and headaches for some users. The number of times per second that the screen is redrawn is called the "refresh rate." A refresh rate below 75Hz can produce a flicker on the screen, so the higher the refresh rate, the less flicker the user will see and the less discomfort they will experience.

How does the refresh rate relate to the capabilities of the video system on the PC? The monitor has a limit as to how much data it is can receive, which is called its bandwidth. At lower resolutions, almost any good monitor/video card combination can produce output at higher refresh rates and still be within the limits of their capabilities. It’s at higher resolutions that the limits begin to become apparent.

While a monitor must be able to receive data from the video adapter, the video adapter must also be able to send data. The adapter sends data via a digital-to-analog converter, also known as a DAC. The DAC speed is a feature of the video card and will change depending on the make and model of the card.

With all of the combinations of monitors and video adapters available today, it would be next to impossible to provide a chart listing the specifications that would have any kind of relevance to a real-world situation. Suffice it to say that it is important to check the specifications of both the monitor and the video card to make sure that they support the resolutions that are required in an organization. You'll also want to make sure the display has enough bandwidth to support a high refresh rate at high resolutions and that the video card has enough RAM to support higher resolutions and color depth.

Dot pitch
Dot pitch is still a good metric to use to compare the potential quality of a monitor, but some caveats may prevent an apples-to-apples comparison.

For example, in CRT monitor construction, there are two basic types of tubes: a shadow mask tube and an aperture grill tube. Each of them uses the dot-pitch measurement term but in a different way.

In a shadow mask monitor, a thin piece of metal with holes cut in it is placed between the electron guns and the phosphors that light up the display. The beam of light is shone through this mask, which produces an image. With an aperture grill tube, on the other hand, the image is created when an electron beam is shone through the gaps between hundreds or thousands of thin metal wires that run horizontally up and down the display. In general, an aperture grill monitor will produce a brighter display, while a shadow mask will sometimes produce a crisper display. (Please bear in mind that these are huge generalizations and can vary wildly from one manufacturer to the next. Sony’s wildly popular Trinitron display, for example, is based on aperture grill technology, and it produces a bright, crisp picture.)

In shadow mask construction, the dot pitch represents the distance, measured in millimeters, between the holes in the shadow mask. With aperture grill construction, the dot pitch is the distance to the next closest slot that passes an electron beam of the same color. Screen colors are made up of red, green, and blue, so in the absence of color on a monitor, it shows black. When all three of the electron guns are firing at full burst, white is produced since all of the colors are mixed. That’s why it is important to be careful when comparing the dot pitch of two monitors.

Conclusion
There is much more to video technology than just basic display settings. Monitor and adapter technology has progressed to include many obscure, yet fundamentally important, settings that affect the overall output on the screen. By tweaking these settings, you can cut down on user discomfort caused by screen flicker.

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