Screen Technology and Sub-Pixels Up Close
A quick guide to screen technology
Examining screens and their sub-pixels up close can tell us what type of display technology is used in a particular product. This in turn gives us an idea of what a screen's main qualities and faults are likely to be!The screen in a TV, a monitor, a tablet or a smartphone is the part of the device where images are displayed. The screen comprises a panel, various filters—notably anti-glare filters—liquid crystals (apart from in plasma and OLED screens), plus transistors and a motherboard to control the whole lot.
A TV screen
- TN: an entry-level technology that can be identified by its poor vertical viewing angles—when you look at the screen from below it looks black.
- MVA: more consistent viewing angles in all directions.
- PVA: similar to MVA but with better contrast.
- IPS: the LCD technology with the widest viewing angles.
The main screen panel manufacturers are currently Samsung, AU Optronics, LG and CMO.
In the past, we thought that these were the only types of screen technology out there. However, it now turns out there are more!
Better Than PVA and ASV: PSA and UV²AWe've long believed that LCD panels all fall into three main categories:
- IPS, including variants such as Super-IPS, Advanced-IPS and, more recently, PLS,
- the various forms of VA panel (PVA, S-PVA, ASV and MVA),
- TN technology.
However, we recently discovered there are three other types of screen technology that we knew nothing about. Although we've often come into contact with them, they're been incorrectly interpreted and identified in our tests due to a lack of information on their existence.
- Since 2003, Samsung and AU Optronics have been making an even higher-end screen than the PVA panel, used in the most expensive LCD TVs on the market. This technology is apparently called PSA and can be found in the likes of the Sony HX923, and the Samsung D8000 series and ES8000.
- Since 2009, Sharp and Chimey (CMO) have been making a more advanced version of ASV/MVA (which are closely related) that's similar to PSA. This is called UV²A, and can be made with three sub-pixels or with four sub-pixels, as seen in Sharp's Quattron TVs.
- Panasonic has recently started making its own IPS LCD screens. This technology is apparently called FFS, but it's something that we still need to check out and confirm (this article will be updated as we gather more information on the subject).
Below you'll find a round-up of screen technology in chronology order, charting the development of the main technology types over time. This includes close-up pictures of the various screen types and their differing sub-pixels.
1971: First TN LCD screen
1984: First colour LCD screen by Thomson
1985: First LCD for IT products by Matsushita (which later became Panasonic)
Sub-pixels in the TN screen in the DGM L- 2262Wd monitor.
As you can see in the picture above, the sub-pixels are large and consistent in size and shape.
1996: IPS: Invented by Hitachi
Response time stayed at 50 ms for a long time, which led to very strong ghosting in these screens. Early IPS displays were particularly popular among imaging industry professionals for their colour reproduction, consistent display quality across the screen and wide viewing angles.
1996: VA: Invented by Fujitsu
VA technology soon evolved into MVA, as viewing angles proved problematic.
1998: S-IPS: Invented by Hitachi, Adopted by LG and Philips (IPS Family)
Sub-pixels in the S-IPS screen in the Nec MultiSync 20WGX² Pro monitor.
The response time improved, as did the contrast—by around 40% compared with the first generation of IPS panels. Other types of IPS technology followed, bringing progressive improvements to ghosting and contrast. These include Advanced Super IPS, Advanced True White IPS, Super-Advanced Super-Fine TFT, etc.
These improvements resulted from slight modifications such moving the sub-pixels closer together, which in turn improved contrast.
1998: MVA: Invented by Fujitsu, Adopted by AU Optronics (P-MVA and A-MVA) and CMO (S-MVA)
Sub-pixels in the MVA screen in the Samsung LE32S86BD TV.
MVA technology was introduced as the best trade-off of its time between the advantages and disadvantages of TN and IPS technology. The response time was improved (compared with IPS technology, above all), as was contrast and viewing angles (compared with TN technology, IPS screens still did better on that front).
Since then, there have been at lest seven generations of MVA panel.
2000 (or earlier): PVA: Samsung (VA Family)
Sub-pixels in the PVA screen in the Samsung UE40D7000 screen.
This technology, introduced by Samsung, proved to be a real step forwards in screen technology. The responsiveness of the pixels was greatly improved and the contrast measured on these screens broke the 1000:1 barrier for the first time.
In comparison, rival technologies were, at the time, delivering contrast ratios of around 200:1 and 500:1, at best. Viewing angles were also better than in MVA panels, although they were still no match for IPS screens.
2002: ASV: Sharp (VA Family)
ASV technology is closely related to MVA.
2002: AS-IPS: Hitachi (IPS Family)
Advanced Super IPS boosted the amount of light transmitted from the backligthing by around 30% compared with the standard Super IPS technology developed in 1998. This allowed contrast to be upped by around 80%.
2004: S-PVA: Samsung (VA Family)
In S-PVA panels, the sub-pixels comprised pairs of chevrons that the transistors could control independently within a single sub-pixel.
Up (very) close, this means that a green shade, for example, could vary in intensity from one sub-pixel sub-cell to another. From afar, this effect meant that the human eye saw smooth colour gradients and shading, allowing TVs to improve the way colour gradients were rendered.
2004: PSA: Created by Fujitsu, Adopted by Samsung, AU Optronics (VA Family)
Sub-pixels in the PSA screen in the Sony KDL-46HX750 TV.
Here, the cells are square or rectangular and the gaps between the cells of liquid crystals that make up the sub-pixels are very slim.
In practice, using this technology allowed manufacturers to push contrast up considerably—past 1000:1, in fact, as PVA screens often clocked up contrast ratios of 5000:1! This brought LCDs closer to the kind of contrast readings seen in Panasonic's top-end plasmas, which maintained their lead by a whisker.
Sub-pixels in the Sony Bravia KDL-32CX520 TV.
2004: IPS-Pro (IPS-Provectus, IPS-Alpha, Fringing Filed Switch, H-IPS): Created by Hitachi, Adopted by Panasonic (IPS Family)
Sub-pixels in the IPS screen in the Panasonic TX-L47DT50 TV.
IPS-Pro allowed 20% more light to filter through from the backligthing (notably by moving the electrodes, which also helped push down power use). It also boosted contrast by 25% compared with the previous generation of IPS screens—AS-IPS from 2002. Between the first generation of IPS screens from 1996 and this generation, the typical contrast ratio of the screen had more than tripled (an index of 100 to 313).
Panasonic, initially a plasma-only brand, started using LCD technology in 2010 with this kind of IPS panel. These days it seems to have become the firm's priority, even ahead of plasma TVs, it seems.
Thanks to Blue Apple
2005: A-MVA, P-MVA, S-MVA
Here, there are even more sub-cells for more variations in hue in colour gradients. This kind of technology was, for example, used in the Samsung UE-40B6000 (CMO, BN02).
2006: H-IPS: LG/Philips
This technology was used in LCD monitors.
2009: eIPS: LG (IPS Family)
This was a low-cost version of S-IPS developed by LG. In theory, some of the qualities of IPS technology were diminished in this particular off-shoot, although power use proved to be lower.
In practice, this kind of screen (used in monitors) still did a pretty good job, and helped bring IPS technology to a wider range of users at a time when it was still quite expensive.
2009: C-PVA: Samsung (VA Family)
This new generation of screens apparently simplified the shape of the sub-pixels, allowing Samsung to reduce production costs. These screens were used in monitors.
2009: UV²A: Sharp, CMO (VA Family)
By switching from chevrons to this new layout, Sharp practically doubled the contrast (x1.6 according the the firm's data), halved the response time of the sub-pixels and gained 3D compatibility.
Production costs were trimmed too, and power use dropped by 20%. While this sounds like a flashy marketing description, it's more easily put into perspective when you see an up-close zoom of the sub-pixels in the new type of technology compared with those in an ASV panel:
2010: Four-Colour UV²A: Sharp (VA Family)
Sharp then developed a version of UV2A with an extra yellow sub-pixel. The first generation had a few teething problems as colour reproduction was way off the mark. However, Sharp put things right in the second generation, released the following year.
2009: AMOLED: Samsung (OLED Family)
Sub-pixels in the AMOLED screen in the Google Nexus One smartphone.
As well as reducing power consumption, the AMOLED screen brought a perfectly black black to screen technology for the first time. However, resolution was lower than in phones using LCD screens. Plus, Samsung couldn't keep pace with the drive to load all star smartphones of the day with AMOLED screens. The Google Nexus One and HTC Desire therefore had to switch back to Super LCD.
2010: Super AMOLED Plus (Active-Matrix Organic Light-Emitting Diode): Samsung (OLED Family)
Sub-pixels in the Super AMOLED Plus screen in the Samsung Galaxy S II smartphone.
Here, we're no longer in the realm of LCD screens—as AMOLED screens use OLED technology, which stands for Organic Light-Emitting Diode. There's no need for a separate backlighting system in this kiind of screen, as each sub-pixel emits its own light. This makes for 'infinite' contrast (i.e. it can't be measured, and the human eye perceives a perfect black) and power consumption can be further reduced.
2011: PLS: Samsung (IPS Family)
Sub-pixels in the PLS (1280 x 800 pixels) screen in the Samsung Galaxy Tab 10.1.
Samsung claims to have reduced production costs of IPS technology by 15% with these new screens and cells, while also improving pretty much all the qualities of IPS technology—including viewing angles. Power use has been reduced too.
Sub-pixels in the PLS (2048 x 1536 pixels) screen in the New iPad.
The sub-pixels in Apple's new iPad look a lot like those in AS-IPS screens.
2011: OLED: Sony (OLED Family)
2012: W-OLED: LG (OLED Family)
LG has added an extra white subpixel to the standard red, green and blue subpixels in its OLED panels. This boosts screen brightness and improves lifespan. The blue LED is more fragile than the other colours—as LG openly admits. It's therefore been made smaller and isn't used as much as the other coloured cells so as to prolong the panel's lifespan.
2012: S-PVA: Samsung (VA Family)
A new variant of Samsung's S-PVA panel with vertical chevrons, seen in the Sony Bravia KDL-40EX653
2012: IGZO Technology by Sharp
Subpixels in a 10" IGZO screen (1366 x 800 pixels)
These new screens are designed to reach resolutions up to UHD (or 4K or Ultra HD)—that's four times Full HD!
2012: Unknown Technology, VA Family (Derived From PSA)
Subpixels from a panel seen in the Haier LET46Z18 TV, sold in certain European countries
2013: Unknown Technology: AU Optronics or CMO? VA Family (Derived From PSA)
Could this be the same screen panel? This time spotted in the Haier LET39Z18
2013: Plasma: LG, Panasonic, Samsung
2013: IPS: LG
LG Display's IPS technology is used in a majority of 2013 TVs, including models made by LG, Sony, Panasonic and Philips. The photo above is from the Panasonic TX-L47ET60. Viewing angles are wider than with MVA, PVA, ASV and UV²A but the black isn't really deep enough, which makes contrast a little low. In fact, contrast maxes out at 1100:1 on the best models with Edge LED backlighting. One solution would be to switch the Edge LED backlighting system for Full LED, with diodes covering the entire rear of the screen surface. This, however, is only seen in a handful of TVs, as it doesn't come cheap!
Many of these images result from our own tests, but we also used the following sources:
- Wikipedia : LCD
- Wikipedia : LCD
- Wikipedia : IPS
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