Painting With Light, Part 1

A Vision of Monitors

Introduction
A computer monitor image is painted with light; that is, what you see is visible via transmitted light. This differs from a painting, a cereal box, or a newspaper in that they use reflected light to be visible, hence the name of this series of articles. It's borrowed from the name of an interesting book on cinematography from 1949.

I'll try not to get too bogged down in technical details or brand names, but I will do my best to provide useful information. I should also make it clear that I do have at least one bias: I feel that LCDs are a niche product, and not the best choice for most users. We'll start in the past, study the present, and look to the future of monitors.

Along the way, we will link to tips on proper setup and useful ergonomics. It's easy to take a monitor for granted, yet it's one of the main interfaces between the computer and the user. Set up incorrectly, it can cause eye strain, neck kinks, and other annoyances. I'll try to give some tips there, as well.

A little history
In the early days of computing, most systems used punch cards for input and printers for output; few systems used video monitors or even keyboards. By the early 1960s, researchers came to realize that a monitor and keyboard provided improved interaction and, in some cases, the ability to display graphics. By the early 1970s, the first video terminals became available. Also known as "glass teletypes", they were primarily text-oriented. The first personal-computer video-graphics card, the Cromemco Dazzler, appeared in late 1976. At the time, it was common for a computer store to run a program called Kaleidoscope on a TV or color video monitor in the store window -- which led to traffic jams around the first computer store in San Francisco.

In the early days of personal computers, the text and graphics output available was within the capability of TVs and TV-compatible video monitors. The Radio Shack TRS-80 microcomputer, for example, used a modified RCA black-and-white TV (minus tuner) for display. Though the Commodore PET 2001 had a built-in monochrome monitor, the Apple II and Atari computers used an external TV or video monitor. These computers all had a 40-character-wide display, so a TV was good enough.

This changed for the mainstream user with the introduction of the IBM PC in late 1981. The original display cards could display up to an 80-column screen, beyond the capability of a TV or even a TV-compatible monitor. This set us on the road that we are currently on -- larger and larger screen sizes, with higher and higher resolutions.

The early IBM PC video came in two flavors: Color Graphics Adapter (CGA), with a 640 x 200 pixel display (80 columns x 24 rows of characters in up to 16 colors or dot-addressable in up to 4 colors) or Monochrome Display Adapter (MDA) which was text-only. Both used digital video, as opposed to earlier personal computers which were TV-compatible and analog. This was followed in 1984 by the Enhanced Graphics Adapter (EGA) which could display more characters and up to 64 colors (though not all at the same time). By the way, pixel is NASA-speak for picture element -- in essence, an image dot.  The term originated with data sent back from lunar probes in the early 1960s.

The next big step was the introduction of the IBM PS/2 series, which featured Video Graphics Array (VGA) display technology. This marked both a higher resolution and a return to analog video.  This lead to more colors, limited mostly by available memory on the graphics card. Starting at about 64 Kbytes at the time, most current cards sport 8, 16, or 32 Mbytes.  Now cards are available with up to 256 MB on-board, since colors x resolution = required memory). We'll cover video adapters in a future installment.

As resolutions grew ever higher, larger screens were required. The first VGA monitors were 12- or 13-inch diagonal and featured 640 x 480 resolution and 16 colors (this was due to memory limitations--256 colors were available at 320 x 240).  These numbers grew quickly as video cards added memory.  Most computer monitors now are 15- to 19-inches diagonal and feature resolutions of up to 1200 x 1600. This brings us to the present.

Monitor types
Let's discuss the two major types of monitors that are currently available: Cathode Ray Tube (CRT) and Liquid Crystal Display (LCD).

A CRT display is the one with a picture tube, like a TV. To say it's "mature technology" is to speak the truth, but there have been a number of refinements over the years. Most of the technology is in the CRT itself. Newer tubes have flatter, squarer faces and are shorter front-to back, but provide much the same image that they have for years.

An LCD is based on newer technology. It can be used where a CRT cannot, in a laptop PC, for example. How can a crystal be liquid (or a liquid be a crystal)? The physical process goes something like this:

• Take certain long-chain oily molecules.

• Lay them out in parallel on a glass substrate. Put another piece of glass in front of it.

• Put a polarizing filter in front of the "sandwich".

• Shine a light through it. See the light? Good.

• Apply a polarizing electric field across the sandwich.

Voila -- darkness! But the light's still shining behind the glass -- what happened? The oil molecules are polar, that is, they line themselves up so as to neutralize the inherent charge which is built into their molecular structure. When we applied the electric field, the molecules twisted according to their polar structure. The light passing through shifted polarization, and is now blocked by the polarizing filter. Imagine this process happening at three million points across an LCD screen and you have the idea of how an LCD works.

Some pros and cons for each technology:

CRT Pros:

• Less expensive.

• Higher contrast.

• Multi-resolution compatible.

• You probably already have one.

CRT Cons:

• Bulky, heavy.

• Higher power consumption.

• Some radio frequency radiation is emitted.

• Only analog inputs available.

LCD Pros:

• Lighter, less bulky.

• Lower power consumption.

• Less radio frequency radiation is emitted.

• Digital input available (DVI).

LCD Cons:

• Much more expensive (though this is improving).

• One optimum resolution (based on a fixed number of pixels).

• Lower contrast (varies with price)

• Viewing angle is limited.

• Slow response time (leads to ghosting and streaking with fast-moving images).

• Lifespan unknown (varies with fabrication technology).

For me, the LCDs' drawbacks outweigh their advantages, especially when decent CRT monitors can be bought used, cheaply.

Ergonomics -- the human factor
Rather than write extensively on this subject here, I will refer you to a couple of web pages, which I found by doing a search on "monitor ergonomics":

http://www.office-ergo.com/viewing.htm

http://www.office-ergo.com/setting.htm

This looks like a good site for ergonomic information overall.

The future of monitor technology
In the next part of this series, I will discuss the following technologies:

• Organic light emitting diodes (oLEDs).

• Plasma displays.

• Digital Light Processing (DLP) displays.

• 3D displays.

• Transparent transistors.

Last revised: 27-May-2004.  Copyright © 2004 Michael Rudas.   All rights reserved.   The opinions expressed in this article are not necessarily those of the other members of the Oak Park Computer Club.   All trademarks are the property of their respective owners.   This article was created using the EditPad Classic text editor and OpenOffice.org 1.1.0 word processor, both free.   Permission is hereby granted to publish this article in an unmodified form, except for formatting (contact me for changes or updated versions).   Technical questions and help requests can be directed to my tech-support mailbox, the link to which can be found on this site or the OPCC site.