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In the Forums... |
Posted: May 28, 2000 Written by: Tuan "Solace" Nguyen Your Best Pitch (cont.) For a shadow mask display, dot-pitch is measured horizontally because the RGB dots lie in a triangular layout (refer to images back on page 3). When you see a shadow mask display boasting a dot-pitch, multiply it by 0.866 because the horizontal distance between the next same color dot is 0.866 times the dot-pitch. Because of this, you should multiply the same number for aperture grille pitch to get a fair result for both technologies. The most common pitches lie between 0.26 and 0.28. Recent innovations have taken the dot-pitch all the way down to 0.22. Visual sharpness is not completely defined by dot-pitch alone; there are many anomalies that can cause an image to lose its sharpness. Geometric Distortion: This occurs when squares and circles don't appear as they are supposed to. A perfect circle can appear slightly oval on the edge of the screen because of curve. This is caused by the intensity of the beam and the angle it is coming from. This can be explained by using a flashlight. Take a flashlight, sit at one spot in the room and shine it straight at a wall. Now, slowly move the beam to one side of the wall and the original circle dot won't appear so circle like anymore. This is the concept of geometric distortion.  Now, considering that the wall is flat, if the edges of the wall were to curve in towards the light source, then it would be like aiming the beam at the center -- producing an accurate dot. This is the way "perfect flats" tend to very slightly warp an object at the far corners (hardly noticeably). This is all correctable with onboard beam processing but it is never perfect unless you are using an LCD (liquid crystal displays -- the displays that laptop use, and recently, desktops). Ghosting: This occurs when one pixel's glow leaks onto another pixel. This causes the image to seem slightly faded or winded to one side. This can be extremely annoying when viewing text or sharp and precise schematic diagrams. Misconvergence: This occurs when the three electron guns (RGB) misalign with each other on a specific pixel. The intention is to have all three beams strike a pixel at the same time. But sometimes this doesn't always happen and you may get colours that bleed onto other colours or edges that are not so sharp. Conclusion Hopefully everything you've just read about how a monitor works will go a long way in helping you on your next purchase. Remember, long after your nice Pentium III or Athlon becomes your favorite doorstop, your monitor will likely still be with you providing thousands of hours of visual splendor (depending on the one you get.. hehe). So invest in a good monitor, one that will serve you well into the future. Or, perhaps you're now more interested in those flat LCD displays that burns holes in wallets. Want to know how they work? Tune in next time… :) Click here to see a printer friendly version of this guide |
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