LCD Technology Part 2: Panel Types & Inputs

The first part of this guide focuses on common LCD definitions, while this article provides an overview of the three major panel types used by LCDs, as well as the backlighting schemes and different inputs. For deeper reading, consult Wikipedia’s entry regarding the main LCD types.

1. TN (twisted nematic): Most commonly used on nearly every laptop ever made, budget desktop monitors, and some cheaper TVs, small screens like navigation systems and phones, TN panels are the most cost effective:
+ Cost of production
+ Fast pixel response time and low input lag
+ Good contrast ratios on good TN panels
- Poor vertical viewing angles and mediocre horizontal viewing angles
- Usually 6-bit color (262,144 colors) with dithering to mimic 16.7 million colors. Most TN panels are advertised as having 16.7 million colors, but beware that they are not capable of reproducing that many true colors
- Poor white and black reproduction, with whites appearing tinted and blacks slightly gray
- Due to the low price of most TN panels, the backlights are generally sub-par (see backlight section below)

2. IPS (in-plane switching): Found in the most expensive LCDs by Apple, Eizo, etc., IPS costs the most to manufacture but provides the best widest viewing angles and most accurate colors. There are several variations of IPS panels, including S-IPS (super), AS-IPS (advanced-super), and IPS-Pro:
+ True 16-bit color with 16.7 million
+ Usually has high color gamut (92% NTSC or better)
+ Best and most consistent vertical and horizontal viewing angles of all panels
+ Very good contrast ratios, with proper whites and deep blacks (AS-IPS has nearly as high contrast as the best VA panels)
+ Since most IPS LCDs cost a lot, they receive the best backlighting technology
- Cost of production
- Contrast is not as good as the best VA panels
- Slower pixel response time and higher input lag than TN or VA (S-IPS is faster than other IPS types)

3. VA (vertical alignment): Comes in many variations, such as MVA (multi-domain), PVA (patterned), S-MVA, S-PVA, etc, these panels are most prominently put into mainstream HDTVs and mid-range desktop monitors. Sharp also has a similar technology that is called ASV (advanced super view), which is sported by some of its Aquos TVs:
+ Though not always the case with cheaper VA panels, many good models have 16-bit color with 16.7 million
+ Usually has high color gamut (92% NTSC or better)
+ Good vertical and horizontal viewing angles (though not as consistent as IPS)
+ The best contrast ratios, with really white whites and deep blacks
+ Acceptable pixel response time and low lag on better models
- Slower pixel response time and higher input lag than the fastest TN panels
- Viewing angles not as consistent as IPS

In addition to the many different panel types that affect image quality, how an LCD is backlit also has an enormous influence on a display’s colors, sharpness, and lighting uniformity:
CCFL (cold cathode fluorescent lamp): these are slowly being replaced by LED, but CCFL has been around for a long time. They are in tube form, have to warm up before reaching full brightness, and begin losing their luminance slowly over time.

LED (light-emitting diode): more and more laptops are using LED due to the technology’s being more power efficient than CCFL. LEDs can also be brighter and enable LCD panels to produce higher contrast (up to 3,000,000:1 for dynamic contrast on high-end Samsung HDTVs) and higher color gamut (beyond 100% NTSC). Unlike CCFL, LEDs reach their maximum brightness almost immediately and barely fade as they age. Full-array LEDs are expensive to make because color and lighting uniformity is challenging. Cheaper LED backlights can sometimes have poorer brightness uniformity than CCFL.

Inputs:
1. HDMI (High-Definition Multimedia Interface): high bandwidth; carries sound and picture digitally; up to 8 channel, 192KHz audio; 48-bit color; HDMI 1.3 up to 2560×1600 resolution; HDMI 1.4 up to 4096×2160; used with digital video such as HDTVs, cable boxes, etc.,
2. DVI (Digital Visual Interface): the standard for computer digital picture; comes in single or dual-link format; resolution up to 3840 × 2400 depending on Hz,
3. DisplayPort: digital video and audio (though audio can be disabled); open-source, unlike HDMI, which charges royalty fees for usage; at 60Hz, resolution up to 2560 × 1600; 16-bit color; now the standard for business and professionals.
4. VGA (Video Graphics Array): analogue picture formerly the computing standard; not much to know about these other than that they are nearly irrelevant in today’s world.
5. Composite: once the high-end of video for TVs and still exists on some desktop monitors and most HDTVs.

* A note about HDCP (High-bandwidth Digital Content Protection): Intel implemented this digital copyright protection measure, which affects all digital video signal interfaces (HDMI, DisplayPort, etc.), video cards, LCDs, and Blu-Ray/DVD-players and ROMs. Ensure that all of your hardware is HDCP certified if you want to play DVD or Blu-Ray through your TV or monitor.

Whenever I use my properly calibrated 1080p Sharp Aquos with its S-PVA panel, 2000:1 static contrast, 100% NTSC color gamut, I need a long time to readjust to my MacBook Pro’s TN display. The whites on good LCDs make cheaper displays look like their whites are stained and other colors muted.