In Part One and Part Two we broke down ways to classify professional display monitors. In this part, we will look at the terms manufacturers use to classify their display monitors, and see how this correlates with our classification.
What we’ll be covering:
- Display Technologies
- Panel Type
- Response Time
- Contrast Ratio
- Color Depth
- Color Space
- Viewing Angles
- Refresh Rate
- Pixel Pitch
- Power Consumption
I urge you to read the earlier parts first, as well as What is a Video Monitor? before proceeding.
Ever heard something like this: Monitor ABC is better because it has XYZ technology?
Stay away from thinking like that. It’s as worthy as statements like “My dad is better than your dad because…”
Each technology has something different to offer. In some areas a certain technology offers improvements while in others it lags behind other technologies. To claim that a monitor is good or bad simply based on its underlying panel technology is ‘monitor racism’.
Phosphors vs LCDs vs Lasers
A Phosphor is a chemical substance that emits light when electrocuted (couldn’t resist!). For every color (R, G or B or whatever) a different chemical compound is used. Phosphors, like light bulbs, burn out over time, and lose efficiency and quality as time progresses. This has a weird effect, called burn-in:
When the same image (static) is projected over a period of time, some phosphors work more than others, and degrade faster. This isn’t desirable at all for professional display monitors.
LCDs are a sandwich of tiny panels (like lasagna) that shape light. Liquid Crystals don’t emit light, only shape them. That means light has to be supplied from elsewhere. Traditionally, this light has come from (still is) fluorescent lamps, but today, the technology is moving towards LED back-lit displays. LED shoots light, and the crystals shape them with the help of the sandwiched technology. Color is produced by Color Filter Arrays (CFA), just like light-gels or your average camera bayer sensor.
Do LCDs suffer from burn-in? Not the way phosphors do, but they have something similar, called Image Persistence. Ever seen electrical switches that get stuck when not used for years? Crystals that get the same voltage (static image) for long periods might get ‘stuck’ in its light-shaping shape. The effect is similar to burn-in, even if the name isn’t:
In addition to image persistence, LCD pixels also have the problem of dead or stuck pixels, and most consumer grade manufacturers (and even some professional display monitor manufacturers) don’t guarantee 100% perfect pixels. Read the fine print to know more about how your preferred manufacturer deals with dead pixels and image persistence.
Lasers are the ‘coolest’ lights in the universe. The practical value of lasers is as close to ‘light elixir’ as we’ll get. Just like phosphors, we need three different lasers for each color R, G and B. Lasers are lights that have very strong intensity, so they can be projected across long distances with insignificant loss in power. The technology for projection systems is moving towards lasers for this reason.
The great advantages of lasers are:
- they have potential color gamuts close to what the eye can see,
- don’t lose quality over their lifetime,
- zero image persistence, and
- they can be projected over any surface (ever seen laser pointers?).
The main disadvantage is cost. Only the highest quality lasers can be precise, and they come at a huge price.
Why we have screensavers
Screensavers were invented to eliminate image burn-in and persistence problems. They change the scenery. However, if you’re working on systems for long periods of time, you don’t want a screensaver popping up every few minutes.
Here are some ways to eliminate or reverse image persistence:
- Change the desktop theme or layout so common elements move from their original places
- Switch off the panel for a few days
- Display a full white screensaver for a few hours or days
- Or just use screensavers and live with it!
Here are a few technologies that you should be aware of:
- CRT – Cathode Ray Tube displays, the standard for many years, still relevant for some applications. But on its way to extinction (unless someone comes up with CRT-2). It uses phosphors.
- LCD – Liquid Crystal Display, the current world champion for consumer grade and professional display monitors, in volumes of units sold. It is more energy efficient than CRTs and takes up less space.
- TFT LCD – Thin-Film Transistor, a ‘circuit’ in your typical LCD to give it life – in other words, improve performance. Today, TFT LCD is LCD.
- IPS LCD – In-Plane Switching. The orientation of the crystal was changed to get wider viewing angles and better color. Going forward, IPS TFT LCDs might be LCD.
- LED – Light Emitting Diode. A cluster of three color LEDs, usually R, G and B. Don’t confuse them with ‘LED back-lit LCD displays’. The main advantage is, it emits light on its own, which means thinner displays (no need for an additional back-light panel like LCD displays)
- OLED – Organic Light Emitting Diode. Silicon is a chemical element, inorganic in nature. Instead of using inorganic LEDs, what if we could use organic ones (For you nerds, the presence of Carbon makes something organic)? You can start warping them:
- AMOLED – Active Matrix OLED. An OLED in which the color array is actively maintained by circuitry. Nothing fancy, it makes OLEDs behave like LCDs. This technology gives Plasma a run for its money.
- Plasma – Uses phosphors. Power consumption is as high as CRT monitors, but can be made to large sizes. Excellent black levels because it doesn’t need back lighting. But guess which other technology doesn’t? That’s right, LEDs.
- DLP – Digital Light Processing. Think about rows and rows of small mirrors, called micro-mirrors, all dancing and reflecting light due to their position (on or off). Anything in between on and off is used for grayscale values. A single-chip DLP display uses a color wheel to produce colors, while a 3-chip DLP display uses a a prism to split light into three components – one for each chip. Since DLPs, like LCDs are light-agnostic, you can throw any type of viable light at it, like LED or Laser. This has a huge advantage – in cinema projection systems you don’t have to buy a projector from scratch every time the light dies. Just replace the lamp, and you’re done. DLP also claims the widest color gamut.
- LCOS – Liquid Crystal on Silicon – similar technology to DLP, except this one uses liquid crystals instead of mirrors.
Here are their ‘sizes’ compared:
As you can see, LEDs and Plasmas can get really thin because they don’t need back-lit panels. Nor do they have to bounce light around.
You could write pages outlining the advantages and disadvantages of each of these technologies. And then, you can add more sub-pages for variations from each manufacturer. By the time you finish reading the whole list, something new will have come up! If you want a simple overview, check out this Wikipedia article.
So, which technology is best? Nope, we’re not going to fall into that trap, are we? I don’t care what the underlying technology is, because I already know what I want. All I care about is whether ‘so and so’ panel gets the job done, or not.
In Part Four we’ll cover the rest of the terms and see how and when to use them.