‘High Definition’ Has Evolved a Lot in 100 Years
We recently spotted a note that said that it was 100 years since inventor John Logie Baird had first demonstrated his TV system to members of the Royal Institution (a scientific society based in London). However, we then found a brief YouTube video showing the man himself introducing his TV and he put the date at January 27th 1926 (although other sources say the 26th!), so just slightly less than 100 years, when we published this article. However, it seemed like a good time to look back on the history of TV and especially the evolution of the quality of imagery. There have been many times when ‘high definition’ improvements have been claimed.
Mechanical Systems of TV
Baird first experimented using the ‘Nipkow disk’, invented in 1884, but applied the technology to broadcasting. On 2nd October 1925, he transmitted a 32 line vertically scanned greyscale image at 5 frames per second. By 1927, he had moved up to 12.5 images per second. On 3rd July 1928, he showed the first color system. In 1928, a transmission. was made across the Atlantic and by 1929, the BBC started transmissions. The resolution was 30 lines, based on Baird’s mechanical system.
(There’s an interesting video showing the principles of mechanical TVs here.)
‘High Definition’ Arrives
The first ‘higher definition’ system started in 1936 with Baird’s 240 line system and a version developed by EMI of the UK, with Marconi, to use electronic scanning to get up to 405 lines. This used a cathode ray tube (CRT) (invented by Karl Ferdinand Braun in 1897) and by then improved for TV use. Baird added colour using a monochrome CRT with a disc with colour filters (a bit like a modern one-chip DLP projector! – Editor). The 405 line system used interlacing to achieve its ‘high definition’. The 405 line system was in use in the UK up to 1985 (although ‘high definition’ 625 line TV arrived in the UK in 1964 with BBC2).
By this time, many were working on different approaches and in the US, the FCC adopted a 525 line monochrome system in 1941. Although a color system using filters was approved it was not adopted widely and was replaced in 1953 by the NTSC color system, which was compatible with existing 525 line systems. By separating the colour and luminance information, it allowed existing owners of monochrome TVs to continue to display the signals.
In most of Europe, PAL was the main color system used and was developed by Telefunken of Germany in 1962 with broadcasts starting on BBC2 in July 1967. SECAM was developed as an alternate color system and used in France and Russia, as well as parts of Africa.
Analog Persisted for Decades
These three analog color standards, 535 line NTSC and 625 line PAL and SECAM were the broadcast systems used for decades. CRTs were used to display the images with a shift from circular tubes to rectangular from the late 1940’s to the 1960s. CRT production increased significantly during the second war after the development of radar and they moved from hand made production to mass production.
21″ diagonal was standard for a large TV in 1955, with sizes moving up to as large as 43″ by 1989. Color had been added to the CRT in mass production by RCA in 1954. Rectangular color sets were sold to consumers from 1963. These were of a 4:3 aspect ratio, matching the TV signals of the time.
The quest for higher resolution was continuing. In 1979, a SMPTE committee looked at four systems,
- EIA monochrome: 4:3 aspect ratio, 1023 lines, 60 Hz
- NHK color: 5:3 aspect ratio, 1125 lines, 60 Hz
- NHK monochrome: 4:3 aspect ratio, 2125 lines, 50 Hz
- BBC colour: 8:3 aspect ratio, 1501 lines, 60 Hz
In 1986, the HD-MAC system was proposed, but the displays of the time limited the quality of the image and a decision was made to abandon the analog approach and tie in HDTV to the transition to digital broadcasting. In Japan, the MUSE system for encoding the 1125 line system was developed with test broadcasts in 1989 and regular broadcasts from 1994. The TV sets to show the content were very expensive ($30,000) so by 1994, the Japanese analog systrem was abandoned.
Sony released the KW-3600HD CRT-based TV in 1990 and we found a great video showing how its renowned Trinitron CRT TVs were made here.
The TV World Goes Digital
The development of digital technologies was progressing at the same time as the analog high definition systems. Crucial to the overall move to digital was the development of the MPEG-1 and then the MPEG-2 compression standards which reduced the bandwidth requirements needed for digital transmission.
After MPEG-1 was standardized in 1993, the ITU released the Rec 709 standard for HDTV that specified the 1920 x 1080 (often known as ‘FullHD’) 16:9 format and standardized colors. In Europe, the DVB organisation was formed to develop technical broadcast standards. Although 1280 x 720 (HD) format was considered for adoption, this was viewed as just an ‘enhanced’ format, rather than true ‘high definition’ (although many broadcasters and the EBU were of the opinion that 720 line non-interlaced formats made a lot more sense than going to 1080 lines with interlacing. Tests with consumers confirmed this – editor).
While Europe adopted the DVB standards, broadly, the US had its own ATSC digital format that was released in 1993. Japan, because of its analog system was later joining and adopted the ISDB technology.
Euro1080 started broadcasting in Europe on January 1st 2004 using DVB-S satellite transmissions compressed with MPEG-2. By 2010 there were more than 200 HD channels broadcasting using satellites.
The Display World Goes Flat
In the meantime, at the end of the 1990s, the TV set display market had started to adopt flat panel technologies. While Sharp of Japan was the first and most enthusiastic adopter of LCD technology for TVs, other makers developed PDP panels. In high resolution, LCDs had a clear advantage as PDP makers found it hard to make displays with small pixels. 1920 x 1080 PDPs were only made in large sizes which made them expensive. Eventually, Panasonic made 1920 x 1080 PDPs in the popular 42″ size.
In the US, rear projection TVs had become popular because of the large images but the market remained at standard definition before being superceded by flat panel LCDs and PDPs.
Eventually, PDPs peaked in sales in 2010 and started a period of decline, as LCD costs came down and quality improved. By 2014, Panasonic, LG & Samsung abandoned PDP signalling the end. (Image quality enthusiasts snapped up the last remaining production of Panasonic’s excellent PDP TV sets).
On to Real High Definition!
The quest for better TV image quality continued driven by better compression, semiconductor development and larger and higher quality displays. In 2001, IBM showed 4K content (3840 x 2160) on color monitors and NHK of Japan had built a prototype TV of that resolution in 2003.
In 2012, the ITU published Rec. BT.2020-0 which defined UHD-1 as 3840 x 2160 (often called 4K TV), and UHD-2 as 7680 x 3120 (known as 8K TV). The recommendation also introduced a wider color gamut, Rec. 2020.
Although 4K TV has been widely adopted by streamers and for higher quality content by other broadcasters, it remains something of a niche when compared to the number of broadcast channels in Standard Definition and FullHD. There are 4K Free-to-air TV services in Spain and Italy and there is strong interest in Brazil and China. The US ATSC 3.0 standard supports UltraHD broadcast at high bit rates.
8K Is the High Definition End Game For TV
8K has become (probably!) the end game for consumer 2-D TV spatial resolution as research by Dr Masaoka at NHK showed that at that resolution and with likely TV sizes and viewing distances, most viewers could not tell the difference between real objects and images of those objects. However, there remains plenty of scope to continue to improve other aspects of image quality such as dynamic range and color as well as frame rates.
8K has already been around a while, Sharp showed its first 8K LCD TV as long ago as 2011.
However, Dr Masaoka’s research was based on the idea of a particular size range of domestic TVs. Scalable technologies such as microLED are likely to make huge TVs possible, and then resolutions above 8K may indeed be desired! In immersive large displays, such as domes and LED walls, resolutions are already going beyond 8K.
