If you're looking to buy a flat-panel thin-film-transistor (TFT) monitor, you've picked the right time. Prices are half what they were a year ago, and the technology is vastly improved. On paper or in person, the benefits of flat panel displays are obvious: they are smaller, weigh less, some can be wall-mounted, and are flicker-free. Still, there are some major caveats, and some surprising twists on the technology.
Talk to Me
Until recently, there were no standards for simple things like the digital-video connectors to allow your PC to work with these displays. This caused most manufacturers to either bundle a specific digital video card to drop into a PCI slot in your PC, or build-in analog-to-digital (AtoD) converters so that the analog video card could send a signal to the digital display. Some manufacturers used a connector referred to as DFP, but that is being phased out. Now there are three types of commonly seen connectors with an identical interface: DVI-A, DVI-D, and DVI-I.
Why digital versus analog? The benefit of a digital connection, when used with a digital-capable monitor and appropriate card, is that there is no degradation in the image signal due to the analog conversion process. If the card and display have traditional mini-DIN 15-pin connectors like your old monitor, then it's an analog connection
All of the DVI connectors are mostly identical in appearance (see illustration), being 24-pin connections, with additional holder pins, and available as both male and female configurations. They also come in dual link, and single-link versions where certain pins are either used or inactive. The primary difference between each version letter is that each supports varying resolution levels, and either digital or analog signals.
Here's the breakdown:
DVI-D Dual: up to 2048x1596; digital only
DVI-D Single: up to 1920x1080; digital only
DVI-I Dual: up to 2048x1536; digital and analog
DVI-I Single: up to 1600x1200; digital and analog
DVI-A: up to 1920x1080; analog only.
The other consideration is that DVI-D connectors can be used with both DVI-D and DVI-I receptacles, while DVI-I cables should only connect to DVI-I receptacles, where the cable is on the monitor, and the video card would be the receptacle.
If you want to go totally digital, then when selecting a monitor and video card, you will want to ensure they have DVI type connectors; unless you're perhaps buying a brand-new Macintosh.
Just to think different, Apple created a novel solution to all the connector confusion. All of Apple's current line of TFT monitors use a specific connector called ADC unique to Apple models with the latest video cards. Power, USB, and digital video signals, all flow through a single cable. This helps reduce cable clutter, and continues Apple's long-held practice of allowing the computer to automatically shut down and start-up the display concurrent with the computer itself.
Color Me in Bits
If you're buying at the shallow end of the price point pool, or been tempted by those $350 flat-panels being hyped by the online sales sites, you should be aware that many of the older 15-inch TFT displays on the market don't actually produce 24-bit color. In fact, they only produce 18-bit color, or 6-bits per pixel versus 8-bits per pixel. What this means in simple terms is that you don't get 16-million colors, or "true color," but an approximation where the extra colors are "interpolated" for your viewing pleasure. This allows for unpleasant color shifts, improper color matching, and forget about the sRGB color standard, let alone Pantone colors.
Always be concerned when you see the phrase "24-bit compatible," color, and look for the actual colors availble on the panel. If it's not true 8-bit per pixel on the panel, then it's not a bargain for anything other than word processing. Additionally, if it's one of the older models then it also has other weaknesses we will cover in a moment.
The Backlight Story
For the last couple of years I've warned folks about the backlight issue. I've even written about it in several publications. Still, some people don't get it. Here are the facts: behind the flat-panel display where you see images, there are usually four cold cathode ray tube (CCRT) flourescent lamps which provide the illumination so you can view anything at all. This array is called the backlight.
On early flat-panel displays (and some of the close-out models on the market now) the longevity of these backlight tubes was as little as 10,000 to 15,000 hours. In practical terms, this means if you left the thing on 24-hours a day, one or more lamps (and thus the array) would fail in as little as 416 days. You do the math. While this was not a huge concern for those who use their flat panel primarily for checking e-mail each evening, or light use on their laptop PCs while traveling, it was a major concern for content developers who might use their systems 12-14 hours per day, or even in the entertainment industry where a workstation might run double shifts.
This was why many flat panel makers had 3-year warranties on the montor, but only 1 year on the backlight. The cost to replace the backlight was up to 60% of the cost to replace the entire unit. And until recently when a 17-inch flat panel cost around $2,000 this was a serious consideration, and a strong argument to stick with a traditional CRT glass monitor. Thankfully, this has changed markedly for the better.
The new displays now on the market have a common backlight lifespan of 25,000 hours minimum, and the better ones have rated lifespans of 50,000 hours minimum (see chart). I can say, for me, if I had the choice of one or the other, I'd opt for a model with a longer rated lifespan, and a 3 year warranty on both the display and the backlight.
Light and Dark
Contrast. It's what makes something noticeably different from something else. It's light and dark, black and white, off white and dark grey. Before you alert the snooze police, allow me to get to the point: flat panel displays vary in their ability to display contrast. Early models had a contrast factor of as little as 125:1 for brand-name models, and the most common amount was 200:1 for premium models. Now, you will find that the sweet spot has become 300:1 and some manufacturers have hit the 400:1 mark.
What this means to you is that for many types of applications where you want the best possible picture and color range, the more contrast the better. And this is an example of where your eyes might need to actually see the difference in person to evaluate what this difference means. It's much like the difference in driving a car with a 4-cylinder engine or a 6-cylinder engine; sometimes it's subtle, but it's really there.
Room with a View
The number one complaint of early flat panels found on both desktops and notebooks was the poor viewing angle (I remember this well on my PowerBook 100, by the way), where if you went a little off a front-facing axis, the picture would not be completely viewable; it would be completely blank, or you'd only see a ghost image.
Modern flat-panels are specifically designed to address this complaint, and now sport viewing angles which typically run 80-degrees in each direction (top, bottom, left, right). Be sure you understand how the manufacturer refers to this specification when shopping, since an 80-degree viewing angle top/bottom on a 17-inch model would equal a 160-degree "vertical viewing angle," while an 80-degree vertical viewing angle would only be 40-degrees in each direction top/bottom. Many 15-inch models may have different vertical and horizontal viewing angles, with a 120-degree "horizontal viewing angle" being a good barometer to shop by. Don't you love the people who write the spec sheets?
Persistence of Vision
The primary complaint for content creators with some flat panels is the persistence of the pixel. This can commonly be seen on some notebooks when you scroll quickly, and there is a visible "after image" of the onscreen content. This is due to many TFT displays having slow refresh rates. Basically, the pixels are not redrawing the screen image quickly enough. This can cause some terrible effects when doing video editing. What many folks forget is older CRT displays had this same problem in the early and mid-'90s. Most higher quality "professional" TFT displays on the market now address this issue much better than some of the consumer publications are reporting. Again, go down to a local retailer and let your eyes be the judge on this one. In fact, I just bought a KDS/Radius LCD for my video editing workstation, replacing a dead Trinitron. It's amazing how much more desk space I have, and it works quite well with Adobe Premiere, thank you!
On the technical side, the magic number seems to be about 10ns (nanosecond) refresh rates to eliminate most issues with image persistence on TFT displays.
A Flat World
Some of the other benefits of flat-panel displays could be to your bank account, particularly if you run a business. An LCD can provide a 34-percent power savings compared to a comparable CRT, and each unit can provide a 20-percent cooling power savings in air-conditioned environments due to less heat. If you're ready to take the plunge and migrate to the LCD technology, there's never been a better time. Once you start working with a quality digital flat-panel, mated to a compatible video card, you will never want to go back.
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