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Choosing the Right LCD Monitor to Buy

Fri, 03 Oct 2008 20:58:37 GMT

I've been trying to figure out what makes a good flat-panel monitor for computer programming for a good while now.

I'm trying to figured it out so I went to this blog post and discovered the follow website with advice from someone who works in the LCD monitor industry on buying a monitor.

LCD technology and tests

LCD monitors are rapidly becoming shipped with new computers by default, and are superior to the old CRT screens for the majority of applications. Although liquid crystal displays boats perfect image geometry and should be perfectly sharp, in reality they still have shortcomings:

Viewing angle dependancies
Poor blacks
Motion-blur

are still issues, particularly for photographic and LCD television applications. Certain flicker or shimmers can be caused by sub-optimal user-adjustment, or shortcuts taken at the factory. On this page I explain a little of LCD screen technology and give you some pointers to the factors which separate teh best from the rest. A large number of test patterns are provided to aid in setting and diagnosis of your display.

Active-matrix LCD technology

A modern desktop liquid crystal display (LCD) computer-screen consists of an active-matrix panel and polarizers (which together act as an electricilly-controlled pixel-level light filter) situated immediatly in front of a backlight (large-area uniform light source - usualy consisting of one to four cold-cathode florescent lamps (CCFL), a lightguide diffuser). The panel is connected to a dozen or so row- and column-driver chips which address the display with the picture data, and are driven by the rest of the monitors electronics. I'm not going explain the basics of LCD panel in any more detail - this is already covered on hundreds of sites.

LCD vs. CRT

The table bellow shows the main factors differentiating LCD and CRT displays from a users' perspective.

LCD	CRT
compact	bulky
lightweight	heavy
low power (c. 20W)	high power (c. 150W)
perfectly sharp	limited sharpness; tend to blur more at high brightness, and with age
perfect image geometry	tends to suffer from geometric distortions, which may be picture (brightness) dependent, and worsen with age.
"consistent" tonal scale	strong bright areas can cause other regions of the picture to dim.
excellent text contrast	poor text contrast (limited bandwidth)
do not normally flicker	inherently flicker (although peoples sensitivity varies)
constrast/colour change with viewing angle)	constistent image irrespective of viewing angle.
poor black on dark images	good blacks (quality monitor, properly adjusted)
native interface would be digital (e.g. DVI)	naturally suited to analog interface
image can be sub-optimal with analog interface

On the basis of image-quality alone, in my opinion LCD is the montor of choice for "office" and technical/CAD applications (largely text-based, or detailed but colour-non-critical graphics), while CRT still has the upper hand for high-end photographic/art work and for television displays.
Higher priced LCDs (probably usuing "In-Plane Switching" "IPS" liquid crystal modes) marketed specifically for pre-press or photographic work should have colors which are less affected by viewing angles for that application (IPS tends to have a less- good black-state -lower contrast- however).

"Vertically Aligned" eg "MVA" (Multidomain -VA) boast the darkest blacks, equivalently highest contrast, or any LCD technology, but response time and viewing angle are poorer than IPS.

LCD Tests

Clock/phasing for Analog inputs

LCD panels use discrete pixels and ideally should be connected to the image source via a digital interface such as DVI. In an analog video signal from a computer's "VGA connector" the luminace data for one pixel runs into the next in a time continuum. To properly recover the data back into the correct discrete pixels requires accurate synchronization of a "sampling-clock" in the monitor to the "pixel clock" in the graphics card. Although possible, this can be technically tricky to get right (the VGA output was never designed for this!) Symptoms of incorrect clock/phase settings include blurry or shimmering text, and shimmering on fine cross hatch patterns. The "automatic" adjustment of many LCD monitors is not always successful, and manual tweaking may be needed. It is probably wise to allow the monitor (and PC) to warm up for 5 to 10 minutes before running this test.

Clock/phasing test screen

For an illustrated explanation of what these controls do, and how to use them, see Clock/Pitch and Phase controls

Inversion

In liquid crystal pixel cells, it is only the magnitude of the applied voltage which determines the light transmission (the transmission vs. voltage function is symmetrical about 0V). To prevent polarisation (and rapid permanent damage) of the liquid crystal material, the polarity of the cell voltage is reversed on alternate video frames. Unfortunately it is very difficult to get exactly the same voltage on the cell in both polarities, so the pixel-cell brightness will tend to flicker to some extent at half the frame-rate. If the polarity of the whole screen were inverted at once then the flicker would be highly objectionalble. Instead, it is usual to ahve the polarity of nearby pixels in anti-phase, thus cancelling out the flicker over areas of any significant size. In this way the flicker can be made imperceptible for most "natural" images.

Line-paired RGB sub-pixel
dot-inversion pattern

Row inversion (lower power)
used eg. on laptops

The following test patterns deliberately excite only one polarity-half of the inversion pattern for some common schemes, and one of them should cause your screen to flicker. This is not a fault with the screen, but enables you to find out which inversion scheme your screen uses.

Note: if using an analog-input monitor, the following tests will not be meaningful unless the clock and phasing settings are correct (see previous test).

Warning to anyone who suffers from epielepsyor other extreme flicker-sensitivity: one or more of the tests bellow is likely to make your LCD flicker at 30 to 40Hz.

Row-inversion (also known as line-inversion - likely to be used on laptops.
Line-paired row-inversion - likely to be used on laptops.
Line-paired row-inversion (offset) - likely to be used on laptops.

Dot-inversion (green test) - will flicker with the (non line-paired) dot-inversion schemes.
Line-paired dot-inversion (green test) - will flicker with either of the line-paired dot-inversion schemes.
Line-paired dot-inversion (green test) - will flicker with either of the line-paired dot inversion schemes (offset).

My laptop screen seems to use Line-paired RGB sub-pixel dot-inversion since it flicker's when I view that image.
My screen down at work seems to get thrown off by Line-paired RGB sub-pixel dot-inversion (offset)

On IE, you can switch to full-screen (and back) using F11. You mighta lso want to set the toolbar to auto-hide (right-button menu when in full-screen mode).

Extreme tech:
The inversion patter for any given screen will inevitably flicker to some extend and is not a fault. If it really flickers a great deal then it may indicate that common-electrode voltage has not been setup properly. In that case you might also perceive a "dot crawl" effect on plain colors of medium brightness. A grossly mis-set common-voltage will also make your screen more susceptible to temporary 'image sticking' problems. Common-electrode voltage can sometimes be adjusted by means of an internal preset, or on a manufacturer's configuration screen. (adjusted for minimum flicker on the inversion-pattern)...but doing so would almost certainly invalidate your warrentee. Typically, with optimum setting, the centre of the screen will have minimum flicker on the inversion pattern, while the flicker will increase somewhat toward the left and right edges. If there's a distinct minimum anywhere on the screen, then the setting is pretty close. Note also that the optimum setting is likely to drift over the life of your screen, and may be slightly affected by temperature and the greylevel of the test pattern.
Any adjustments are made at your own risk!

Dot-crawl / line-crawl test page

Now I'm not entirely sure what the dotcrawl test page is supposed to do; I did notice however that the box with the horizontal lines in it did seem to move vertically upwards.

Some diagonal cross-hatch patterns used for shading by CAD programs can interact with inversion and cause objectionaable flicker on some LCD monitors - this should only be a problem if the manufacturer has left the common-electrode voltage grossly mis-set. Having seen the severity of the effect on some new monitors (and how easily it could have been tweaked out at the factory) I'm beginning to for the opinion [January 2005] that in some cases this flicker could argueably be classified as "fault" with the product.

Laptop LCD screens tend to be optimised for lower power, wioth some relaxation of image-quality criterion. As well as (often) lower brightness and less saturated colors, laptop screens usually use 'row inversion' (aka 'line inversion') scheme rather than the dot inversion now universal in desktop screens. If you look closely at a row-inversion LCD, particularly if it is shown a fairly plain, mid-brightness color, you may see a slight horizontal line interference pattern on alternate lines, which may appear to drift up or down on the screen. This is also not uncommon on color mobile-phone displays, or personal DVD players.

Cross-talk

Owing to the way rows and columns in the display are adressed, and charge is pushed around, the data on one part of the display has the potential to influence what is displayed elsewhere. This is generally known as cross-talk, and in matrix displays typically occurs in the horizontal and vertical directions. Cross-talk used to be a serious problem in the old passive matrix (STN) displays, but it is rarely discernible in modern active-matrix (TFT) displays.

A fortunate side-effect of inversion (see above) is that, for most display material, what little cross talk there is, is largely canceled out.

For most practical purposes, the level of cross talk in modern LCDs is negligible.

Certain patterns, particularly those involving fine dots, can interact with inversion and reveal visible cross-talk. If you try moving a small Window in front of the inversion pattern (above) which makes your screen flicker the most, you may well see cross-talk in the surrounding pattern.

Different patterns are required to reveal cross-talk on different displays (depending on their inversion scheme). the following patterns may show cross-talk on your screen.

These patterns are not comprehensive and should not be used blindly to rate one screen against another. The appearance of a visible cross-talk from any of these patterns does not indicate a "fault condition" with your display!

Color, and viewing-angle dependence

Colors displayed by LCD screens tends to vary with viewing angle. Please go to the following page to see this effect:

Color and viewing-angle dependence

I can definitely see this...but I don't think I would have noticed if you hadn't said anything about it. Interesting.

Most low-price 15" and 17" LCD monitors use the Twisted Nematic ("TN") liquid crystal mode; with these displays the image looks much lighter if looked down on from above, and much darker if looked at from bellow.

Yup, that's my laptop's display!

Newer liquid-crystal modes such as Vertical Alignment ("VA"), or In-Plane Switching ("IPS") have less viewing-angle dependence, but may suffer slower response times and/or lower contrast.

Greyscale setup
Although not specific to LCD screens, I'm providing a greyscale test-page for completeness.
Greyscale alignment page

"Bear in mind that the amount of ambient light in your room will affect how the colors display"
Neat I really didn't know about that. Maybe that's why those "brown flowers" I used on that webpage looked to good to me as wall paper when I was at crave

Refresh rate, response time, flicker and motion-blur

There seems to be alot of confusion and mis-infromation on these topics on the we; here's my clarification...

Refresh Rate is the rate at which the electronics in the monitor addresses (updates) the brightness of the pixels on the screen (typically 60 to 75Hz). For each pixel, an LCD monitor maintains a constant light output from one addressing cycle to the next (sometimes referred to as 'sample-and-hold'), so the display has no refresh dependent flicker.
There should be no need to set a high refresh rate to avoid flicker on an LCD.

Ah ha! well that clears up that little line of bull...I've seen 100Hz refresh rates on the net for LCD monitors...hmm makes ya think!

Response time relates to the time take for the light throughput of a pixel to fully react to a change in its electrically-programmed brightness. the viscosity of the liquid-crystal material means it takes a finite time to reorient in response to a changed electric field. A second effect (which ahs a rather more complicated explanation) is that the capacitance of the LC material is affected by the molecule alignment, and so if a step chance brightness is programmed, as the LC realigns the cell voltage changes and the brightness to which it settles is not quite what was programmed. Unless 'overdrive' (which tries to pre-compensate for this effect) is employed, it may take several refreshes before the light output stabilizes to the correct value. Response Rate for dark-to-light is normally different from light-to-dark, and is often slower still between mid-greys. VESA and others define standard ways of measuring response time, but a single figure rarely tells the whole story.

Manufacturers 'response times' rarely tell the whole story. Unless bellow 16ms are likely to be of only marginal benefit, owing to more-dominant 'sample and hold' effects (see bellow).

The visual effect of motion blur is self-explanatory and is fairly intuative to realize that a slow pixel response-time will cause this problem.

Its probably about time I Start a CSS Wiki

Fri, 03 Oct 2008 20:34:54 GMT

I was working a good bit on CSS this week, and I realize that I've forgotten a bit since my high-adieus from web development last year.

For instance the whole float: left; float: right; ... clear: both thing, I completely forgot about that.

Also I've made a good number of toolbars lately (well okay so I made like two), but both would have been made easier/faster with the previous aforementioned tutorial.

Oh and I forgot that CSS3 seems to be rearing it's ugly head (hopefully it's alot nicer than the previous CSS's. (CSS's?)...

So this got me thinking I should really make myself a personal Wiki for all things CSS. I need to drop the whole: "Oh, but CSS is so easy...I don't need a wiki for that..." yeah let your pride go and see what you can really accomplish; write it down!

DefaultTiddlers

Fri, 03 Oct 2008 20:33:47 GMT

3 October 2008 - aleer
30 September 2008 - aleer
23 September 2008 - aleer
17 September 2008 - aleer

3 October 2008 - aleer

Fri, 03 Oct 2008 20:26:47 GMT

Found Great Horizontal Navigation Tutorial

Fri, 03 Oct 2008 17:00:26 GMT

Centering a Horizontal Navigation in a Liquid Layout

30 September 2008 - aleer

Wed, 01 Oct 2008 03:09:00 GMT

Geo-RSS

Tue, 30 Sep 2008 03:08:00 GMT

Today I was looking to using geo-rss, so far I've found an example geo-rss feed here, and I've used dipity to map it out.

My next task is figuring out how to add this to my blog content so I can map my posts, which seems to me that it may have something to do with changing the way the rss feed is generated in tiddlywiki:

Seeing as the RSS feed is generated like this for the example geo rss feed I found earlier looks like this:

<rss xmlns:gml="http://www.opengis.net/gml" 
     xmlns:georss="http://www.georss.org/georss" 
     xmlns:media="http://search.yahoo.com/mrss/" 
     version="2.0">

And my blog's RSS feed kinda like this:

<?xml version="1.0"?>
<rss version="2.0">

I need to find a way to put the three xml namespaces in the rss of the blog.

There also appears to be a microformat for this:

<span class="georss:point" title="43.3432 -69.2341">Here is a point</span>

Here is a point

Ah, I seem to have found a function in the tiddlywiki called generateRss() which generates the headers for the RSS feed, I will either have to override this method in a plugin (if you can do that...) or modify the code myself.

29 September 2008 - aleer

Mon, 29 Sep 2008 18:26:00 GMT

Geo-RSS

Really Good Job Site.

Fri, 26 Sep 2008 20:31:00 GMT

http://www.odinjobs.com

Other Tools

Tue, 23 Sep 2008 19:54:00 GMT

Some followers of GTD advocate a 'back-to-basics' approach to personal management, and a rejection of over-engineered, high-tech solutions in favor of simple, less-expensive tools such as preprinted cards, index cards, the Hipster PDA, or even the Moleskine paper pad.

David Allen himself says he relies on a "vanilla" Palm PDA and records "events of the day" on paper to be processed later.

GTD Tools and Techniques

Tue, 23 Sep 2008 19:51:00 GMT

edit tiddler

Software Tools for GTD

Tue, 23 Sep 2008 19:51:00 GMT

Software was specifically suggested by Allen as helpful and important for implementing GTD, including:

digital outlining
brainstorming
project planning

However in 2001, Allen bemoaned the general lack of "good 'project management' tools, " concluding:

...less structured and more functional applications will emerge in the coming years, based on the wys we naturally thing and plan.

Since that prediction, a virtual explosion of GTD-supporting software has emerged; in April 2008, more than 100 applications provided the core features for implementing Getting Things Done These tools now range from simple list managers to collaborative web services, both free and commercial, for all popular platforms and devices. Much of this software specifically automates or reinforces the GTD methodology of collecting, processing, organizing, reviewing, and doing.

Get Things Done

Tue, 23 Sep 2008 19:46:00 GMT

From Wikipedia

Getting Things Done (commonly abbreviated as GTD) is an action management method created by David Allen, and described in a book of the same name. Both "Getting Things Done" and "GTD" are registered trademarks of the David Allen Company.

GTD rests on the principle that a person needs to move tasks out of the mind by recording them externally. That way, the mind is freed from the job of remembering everything that needs to be done, and can concentrate on actually performing those tasks.

GTD Methodology

GTD is defined by David Allen on his website. In traditional time management, priorities usually play a central role. In contrast, Allen promotes two key elements in his version of time management:

control
perspective

Allen advocates three major models for gaining control and perspective:

A workflow process
A framework with 6 levels of focus
A natural planning method.

The first major model is the workflow process, which is used to gain control over all the tasks and commitments which one needs or wants to get done.

Work Flow Phases

The workflow process consists of five distinct phases listed below:

Six Levels of Focus

Allen uses an altitude analogy to illustrate his second major model, 6 Different Levels of Focus, from the bottom up, are:

As one ascends in altitude, one is able to consider the "bigger picture."
Considering:

projects
actions
unfinished business
commitments

("open loops" in GTD terminology) and other "input" from a variety of "heights" gives one varying perspective.

Allen advocates a weekly review focused on different levels. The perspective gained from these reviews. The perspective gained from these reviews should drive one's priorities, which in turn determines the priority of if and when one is to do the particular individual tasks and commitments gathered during the workflow process. During a weekly review, the user determines the context for the tasks and places them on the appropriate lists.

Examples of grouping together similar tasks include:

Making a list of telephone calls to make.
Making a list of errands to do while downtown.

Context lists can be defined by the set of tools available or by the presence of individuals or groups for whom one has items to discuss or present.

Allen expects that the first two models are sufficient most of the time to gain control and perspective on the majority of tasks and projects. However, there are some cases in which more involved planning and thinking are necessary. This leads to the third major model, which is the natural planning method.

The Natural Planning Model

While the Workflow Model has a "horizontal" focus on doing individual tasks, the Natural planning method has a "vertical" focus on planning projects and thinking through topics.

The Planning Model consists of 5 stages:

GTD is based on making it easy to:

Store
Track
Retrieve

all information related to the things that need to get done. Allen suggests that many of the mental blocks we encounter are cuased by insufficient 'front-end' planning (i.e., for any project we need to clarify what is to be achieved and what specific actions are required to achieve it.). It is most practical, according to Allen, to do this thinking in advance, generating a series of actions which we can later undertake without any further planning.

Allen contends that our mental "reminder" system is inefficient and seldom reminds us of what we need to do at the time and place that we can do it.

Consequently, the "next actions" stored by context in the "trusted system" act as an external support which ensures that we are presented with the right reminds at the right time.

A capsule of GTD from Allen's book Ready for Anything:

"Get everything out of your head. Make decisions about actions required on stuff when it shows up - not when it blows up. Organize reminds of your projects and the next actions on them in appropriate categories. Keep your system current, complete and reviewed sufficiently to trust your intuitive choices about what you are doing (and not doing) at any time.

edit tiddler

Tickler File - GTD

Tue, 23 Sep 2008 19:46:00 GMT

Tools and Techniques

A file that helps refresh one's memory each week with the outstanding tasks and projects.

One device that Allen suggests is the
Ticker File for organizing paperwork (also known as The 43 Folders).

Twelve folders are used to represent each month and an additional 31 folders are used to represent each day. The folders are arranged to help remind the user of activities to be done by that day.

Do - GTD

Tue, 23 Sep 2008 19:40:00 GMT

Any organizational system is no good if excessive time is spent organizing tasks instead of actually doing them. Allen's contention is that if one can make it simple, easy, and fun to take the necessary actions, one will be less inclined to procrastinate or become overwhelmed with too many Open Loops

Review - GTD

Tue, 23 Sep 2008 19:37:00 GMT

The lists of actions and reminders will be of little use if not reviewed at least daily, or when ever possible. Given the time, energy and resources available at a particular moment, one must decide the most important task to be done immediately, and do it.

If one is inclined to procrastinate, one may end up always doing the easy tasks and avoiding the difficult ones.

To solve this, one can decide to do the actions of the list one by one, following their order, just like processing an inbox.

At least weekly, the discipline of GTD requires that all outstanding actions, projects and waiting for items are reviewed, making sure that any new tasks or forthcoming events are entered into one's system, and that everything is up to date. Allen suggests the creation of a Tickler File in order to help refresh one's memory each week with the outstanding tasks and projects.

Organize - GTD

Tue, 23 Sep 2008 19:31:00 GMT

Allen describes a suggested set of lists which can be used to keep track of items awaiting attention:

A calendar is important for keeping track of appointments and commitments; however, Allen specifically recommends that the calendar be reserved for the hard landscape.

To-do items should be reserved for the next action lists.

A final key organizing component of GTD is the filing system. A filing system must be easy, simple, and fun. Even a single piece of paper, if needed for reference, should get its own file if it doesn't belong in an existing folder. Allen suggests a single, alphabetically organized filing system, in order to make it as quick and easy as possible to store and retrieve the needed information.

Hard Landscape - GTD

Tue, 23 Sep 2008 19:22:00 GMT

Things which absolutely have to be done by a particular deadline or meetings and appointments which are fixed in time and place.

Someday/Maybe - Organize - GTD

Tue, 23 Sep 2008 19:19:00 GMT

Things to be done at some point, but not right now.

Examples:

Learn Chinese
Take a diving holiday