Soon, fancy 3D effects and shading became available, and more recently, obvious DVE effects have thoroughly fallen out of favour. Now the DVE has been relegated to the electronic scrapheap as the task of processing TV pictures has transferred away from dedicated machines towards being just another plug-in software routine on a computer.
On many DVE boxes, smart engineers figured out a way to perform a trick that is, at one level, barely noticeable to the viewer yet it quickly became a firm favourite with many directors - the film effect.
To understand the film effect, first we need some background. In the early days of cinema, it was experimentally determined that to avoid flicker while film was being shown, the shutter in the projector should open at least 46 times per second. However, to save expensive film, it was realised that having brought a frame of film into the projection gate, the projector could show it twice and in the 1920s, studios settled on a frame rate of 24 frames per second, yielding a flash rate of 48 Hz. Modern projectors will show each frame three times and the resultant flash rate of 72 Hz virtually eliminates flicker, even at the periphery of vision where the eye is more sensitive to movement and change.
In the latter half of the 20th century, along came television. TV frame rates were established not so much by cinema but by the need for early television equipment to be synchronised with the alternating voltage of local electricity supplies. As a result, the USA used a scan rate of 60 Hz which is just about flicker-free, while Europe used 50 Hz where the flicker is more pronounced.
The frame rates for each region were 30 fps for the USA and 25 fps in Europe, both different from the cinema rate of 24 and both requiring different strategies to get cinema onto television.
In Europe, the most common method for decades was simply to run film through a machine at 25 fps and accept the slight speed-up of vision and sound, even though musicians with good sense of pitch were bothered by all the music being raised about a semitone. If film was shot for TV, it was simply shot at 25 fps.
Whether we see film at the cinema or on the TV, we have all become used to frames of Hollywood being shown to us twice or even three times before moving onto the next. This gives the portrayal of movement on film a distinctive judder which we don't get on conventional video cameras.
Staying with European systems and frame rates, think about someone swinging their arm through the picture. On a conventional video camera, we would see the arm change position 50 times per second. Since this is also the rate at which pictures are drawn on the screen, the motion appears smooth and very realistic. On film transferred to TV, the arm would be in a particular position for two pictures and then move onto another position for another two pictures. The brain tries to make sense of this by perceiving a straight line of movement between the frames but in the process, it not only perceives the slower update of the arm's position as a judder, it also perceives a doubling of the image so that the arm temporarily appears as two arms swinging through frame.
This juddered, broken portrayal of motion has become forever lodged in our heads as the 'filmic' look. In the latter part of the 20th century, TV directors realised that their pictures shot on video cameras, with their smooth, realistic portrayal of motion, could be made to look filmic by exploiting tricks on the DVE boxes whereby each picture could be repeated twice to replicate the juddery look.
One problem with this scheme stemmed from the way TV pictures were constructed. At the time, a single UK TV frame of 25th of a second was built up from 576 lines but that was shared across two interlaced 'fields' of 288 lines, each lasting 50th of a second. The full vertical resolution of the system, 576 lines, required both of these fields. By repeating one field as the other to make the picture filmic, the same information got displayed twice so that the vertical resolution of the filmiced picture was now just 288 lines. In other words, to fire off that nostalgic nerve that yearned for the Hollywood Dream Factory, TV directors not only gave up half of their time resolution, they also lost half of their detail resolution.
Nowadays, much TV output is deliberately shot in what is known as 'progressive' scan at 25 fps. This replicates the judderiness of film shooting while, like film, preserving the full resolution of the source image. The desire to ape Hollywood and decades of staggered movement is strong in directors and producers. But there are signs of change.
Increasingly, shooting for the cinema does not use old-fashioned film and instead, digital cameras are favoured for the savings in cost and the greater control they offer in post production. But these cameras are not limited to old frame rates. Neither are the projectors in the cinema which are also moving to digital projection from a file instead of film.
In 2009, James Cameron released Avatar in which he wanted to audience to have an immersive experience. He created the film in IMAX resolutions and used 3D technology to take people as much as possible to the world of Pandora that he had visualised. When his movie finally hit the IMAX screen, he found that there was one thing getting in the way of that complete Pandoran joyride. The film had been shot and rendered at 24 frames per second and all his carefully crafted three-dimensional movement displayed the old unrealistic judder.
For Avatar's sequel, and Peter Jackson's The Hobbit, frame rates have been increased to 48 in hope of providing a more realistic experience. What was the reaction to the initial screenings? "Ugh, looks like television." Seems nostalgia for the old Hollywood Dream Factory has a powerful hold on audiences.
