Cameras for broadcasters

HDTV has introduced new challenges for broadcasters as quality standards far exceed those imposed by standard definition.
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OpTex’s SDI version of the Toshiba TU63 is designed to enable producers to introduce mini cameras into the studio without compromising picture quality.

A few years ago, things were different. Most major broadcasters had strict codes of practice to which manufacturers, if they were sensible, strictly complied. Everything was set in tablets of stone, and all was right with the world.

These days, things are different. On the one hand, the introduction of high-quality prosumer cameras has arguably opened up new opportunities for producers. At the other end of the scale, HDTV has introduced new challenges for manufacturers, technicians and broadcasters as quality standards far exceed those imposed by standard definition. So the question has to be posed: What exactly is a broadcast camera?

Prosumer versus professional

Let’s put it another way. Do we need a far more flexible approach when it comes to present-day and future requirements? The answer is “yes.” Even the question as to exactly what is broadcast television is now open to multiple interpretations.

It is no longer simply a matter of terrestrial and satellite/cable. Broadcast television also means Web streaming and mobile phones. It means high-definition distribution for E-Cinema. It means considering the needs of content owners when it comes to future-proofing their assets. In other words, it means many different things to different people — all with very different needs and aspirations.

It is not always a matter of cost, and it would be shortsighted to ignore those low-end, prosumer DVCam and MiniDV cameras that are capable of returning pictures that meet technical requirements. Indeed, reading various codes of practice, the main objection lies more with how such cameras are used, rather than the camera or tape format itself. It certainly should not be seen as a cheap alternative — get rid of the camera crew and get the PA to shoot it.

One area that can produce potential problems, however, is 16:9. Current prosumer cameras do not shoot native 16:9, or at least not true 16:9 anamorphic. Different broadcasters have different ways of overcoming this problem, from totally ignoring it in the hope it will just go away to imposing strict rules as to the use of anamorphic lenses or aspect ratio converters. Add to this the practice of transmitting programs in 14:9, and the whole thing becomes a delightful mess.

Equally subject to the widescreen lottery are medical imaging cameras such as the Toshiba TU63. Using 3 x 1/3-inch CCDs reduces the size of such cameras to a mere 40mm cube. Although not designed for the broadcast industry, they are capable of returning remarkably good pictures. Facilities such as a 6-axis matrix mean these tiny cameras can match studio cameras remarkably closely.

Once more, this is a case of finding technical answers to production requirements rather than the other way round. For the television engineer, such thinking can at first seem a little foreign. But once we start thinking outside of the test chart and inside live action, things can take on an entirely new perspective!

High-definition requirements

Not so, however, with high definition. Low-end and mini cameras have given us the opportunity to rethink how we shoot television programs, but HDTV has imposed an equally revolutionary, though entirely different, set of requirements. And again, it has to do with program content. Quite rightly, viewers of HD programs come with high expectations. They are either paying premium rates for the channel — as is the case with Discovery HD Theatre, for example — or they are watching prestige television, as is the case with NHK.

At its most simple, HDTV requires four times the resolution of standard television, although this is somewhat of an over-simplification. The recommended viewing distance for HDTV is 3x picture height. That is close, and it is an entirely different viewing experience. Everything becomes more real, more apparent. It is all very well saying that if the content is there, the viewer will not notice the faults, but that does not hold with high definition.

Camera setup is far more critical. For example, shading errors are more obvious on HD material. Some manufacturers believe that edge enhancement makes HD pictures look better. However, even slight detail enhancement can produce aesthetically unacceptable results. These faults may not be apparent on a test chart — indeed, images may appear superior.

It is even more vital that engineers understand exactly what makes for pleasing pictures, even if this goes against every engineering instinct. Often, such aesthetics are based on the viewers’ experience of watching films. There is something special about the cinema experience, and it does not stop at popcorn. And yet there are many artifacts introduced by the film chain itself. So what is happening? For example, there are certain technical advantages to be had in recording 24p progressive scan, although temporal resolution is not one of them. Many people see progressive scan as being a retrogressive step, and yet viewers actually seem to prefer the artifacts and aberrations introduced by film. We all have to think openly!

But if the temporal aberrations of film are acceptable, optical aberrations certainly are not. Lens design for HDTV is far more critical. It may be tempting to think that you can get away with using standard, rather than HD, lenses. Getting away with it, however, can be extremely expensive. At best, it means not getting invited back for the next show. At worst, the broadcaster can insist on an entire reshoot.

Certainly, any slight optical aberrations such as longitudinal color and spherical aberration will be far more visible on a high-quality HD display, especially under critical test conditions. Even under the less stringent conditions of the viewer’s home, such faults may not be quite so apparent, but they are still there. HD viewers expect more.

Neither does it stop in the engineering workshop. Camera operation too becomes far more critical. Slight focus errors, unless they are part of the story, become intrusive, as do unsteady hand-held shots. For once, it really is a case of “thinking outside the box.” In this case, it’s the little box in the corner, and instead, thinking about the big screen hanging on the wall.

These are exciting times as the whole meaning of television expands. It expands beyond the little 4:3 screen and even the big 16:9 screen. And here is an interesting thought: Measure the aspect ratio of John Logie Baird’s first mechanical-scan televisor, and you will find it was actually 16:9! How far we’ve come — and returned.

Brian Rose is the technical manager for OpTex.