Novel lightning of TV Studios with LED projectors

Author: José María Pérez

NEW LIGHTING PROCEDURES

Actually, current TV programs are the same as or very similar to the ones seen in the past 50 years, such as news, interviews, sports or current issues presentations and commentaries, weather, talk shows, including programs showing outtakes, debates on political issues, current issues or sports, contests, large-format music contests, reality shows, music performances, virtual presentations, etc.

Scripts, developments and types of production have hardly changed, except for the higher quality of capture (more and better cameras, cranes, robotic heads) and video processing (from the old PAL 4:3 to PAL 16:9 and then SDI, HD, 2K up to 4K, with capture cameras of at least 12 bits and internal processors not lower than 15 bits) and, most of all, a huge improvement in visual presentation, including of course sets featuring audiovisual means, but also new lighting effects that had been up now impossible to achieve, playing with color shades, backgrounds, robot-led effects, etc.

NEW DESIGNS FOR SETS

In the past ten years, the design of sets has undergone a spectacular development. For many years, sets used to be opaque and would require outdoor lighting for achieving a fairly joyful image. Duratrans (pictures with back lighting) required a lot of background; vinyl panels would easily reflect front projectors, and audiovisual information was normally contributed by generators of digital effects, either included in the mixer or external ones, as monitors and even videowalls formed by cubic monitors would not reach an intensity to make them stand out by strong front lighting. In this regard, camera sensitivity has also experienced a steady positive evolution.

In order to shed “light” on this topic, let us take into account some technical considerations. In the period 1988-90, with the first generation of CCD cameras, sensitivity of the latest generation of Plumbicon cameras was 2,000/F:11. This means that by applying 2,000 lux on the gray adjustment chart, the diaphragm had to close at F:11 for white to reach peak volt.  In regard to faces, clothing, etc., the limit was also peak volt (so as to avoid saturation of whites in the image, shines on faces or in white shirts, for example). A standard diaphragm for achieving good field depth in general takes is F:8 (twice as much light coming into the camera as F:11), that is, a normal incidence level would be 1,000 lux (half the light) for most programs.

However, the first generation of CCD studio cameras would typically have a sensitivity of just 2,000/F:4 and, in some cases, 2,000/F:5.6. This means that in the best case with an advanced camera, 4,000 incident lux would be required for achieving the peak volt with a F:8 diaphragm., that is, four times more light than with Plumbicon tube cameras and up to 8 times more light for less advanced CCD cameras.

This has nothing to do at all with the message that CCD cameras are able to record with just 10 lux, or under the moonlight, for example. This is true, but with all possible gain being applied, and the resulting image noise. At the same time, modulation depth, dynamic and contrast levels, color intensity, etc., are extremely poor at such levels.  As we are addressing in this article professional quality for a TV program, we will forget all about these levels and concentrate on the professional parameter, which measures the camera’s work with no gain and with Knee correctors applied.

At present, CCD studio cameras work with lighting levels exceeding 2,000/F:11 (normally starting from 2,000/F:12), which means that for F:8 we will only need about 300-600 incident lux, depending on the specific camera.

This is extremely useful as with such levels, new sets massively use LED strips –both white and RGB- that provide enough light (using the most powerful ones of at least 60 LED, 1,300 lumens and 12W per meter) with light diffuser plastics and duplicate strips with dark (red-blue) diffuser plastics, so RGB-type are typically used with milky white plastics for a perfect diffusion of light points.

Additionally, there are power supply units and tension-current controllers with DMX control, wireless controllers, etc. Worth noting is the fact that the huge duration of LED devices allows placing them in locations difficult to access, as no maintenance or restoration work is foreseeable. Naturally, this was unfeasible with halogen lighting, not to mention the heat thus generated, which is so dangerous for sets, this not being the case with LED lights.

For lighting areas and duratrans, there are industrial-quality bar projectors (very usual in discos, showcases, small sets, photo-calls, etc.) up to 300 W, RGB, warm white, cold white (and even black light!) with DMX control and a wide array of fixation possibilities at extremely low prices. None of this either existed or was feasible ten years ago!

Similarly, projection of AV means has switched from monitors and monitor videowalls with grid signal distributors, resulting in an obvious loss in resolution and, simultaneously, the “catches” arising of effect generators, to high-resolution LCD-monitor videowalls with no visible frame at a reasonable cost; and event HD continuous videowalls that produce highly detailed images, even in close-up takes. The latter devices are currently used in nearly all news programs.

Additionally, low-resolution continuous videowalls are used in combination with high-power LEDs for all kinds of sets in large contests, musical programs, etc. Of course, such devices are directly connected to dedicated computers, although they can also be fed with video images of the right format in the manner of a videowall.

None of these items would be viable at the required lighting levels ten years ago or more! The lighting level required back then being 4 or more times the one currently required, would leave these devices quite dark indeed.

OUTDOOR LIGHTING OF SETS, CYCLORAMAS AND VIRTUAL SETS

For lighting of these sets, which are similar in concept, white-colour or -increasingly- RGBAW bars are being used.

For cycloramas there are very high-power professional bars that allow for uniform lighting of up to 8 metres in height, by playing with lighting spots at ground and ceiling level, with the additional advantage of being able to stay quite close to the fabric as compared with the older assymetrical parable projectors. Virtual sets are similar save for the fact that bars cannot be laid on the floor (except in large studios with chroma sheeting at floor level to conceal the lamps). For external set support, RGB bars are used in specific areas to make them darker or to highlight them as background for close-ups.

NEW KEY LIGHTING SYSTEMS FOR STUDIOS

Key lighting is the same as 100 years ago!  Of course, in view of the current sensitivity of cameras, lighting of people, props, furniture, etc., this ranges between 300 and 600 lux, as compared to the at least 10,000 lux required in the initial era of cinema, featuring arc projectors (due to the extreme lack of sensitivity of the first photographic negatives). The basics entail lighting by means of a “hard” light, which sets its own direction through the shadows cast. To this purpose, the projector must have a small projection area –lens- from a point in the axis normally matching the camera of the close-up.  To this end, mostly Fresnel projectors are preferred. As this lighting generates very dark –even black-shadows, these are softened (whitened) with projectors having a really wide screen –in former times the “softlight”- then the cold light screens and, at present, large LED screens, typically 2’x1’ or even 2’x2’, projecting at an angle from a side (a 60º angle on the right and another on the left of the base beam are typical).

This front lighting is supplemented by back lighting in the direction that is opposite to the camera-to-subject axis. This lighting must be extremely focused and accurately trimmed to prevent it from spilling sideways on to other people or props, with the resulting intense white light glimmer. For this reason Fresnels are used, although for certain simple programs such as news, with anchors on a side-to-side position and within the same camera axis, small format panels are also used sometimes, normally lying horizontally (a typical one is 2×1 feet).

Additionally profile spotlights are used to light prop items and even people when cutting out light in some areas becomes a priority (for instance, in order to prevent the light from being reflected on videowalls). At preset there are LED profiles of up to 300W, which are equivalent to 2kW halogen profiles.

Of course, the projected light must be in keeping with background lighting, so a good control system is therefore a must. Nearly all LED projectors feature DMX control, so this is not really an issue.

This general set-up is possible at present only with LED projectors. However, some issues and their potential solutions must be noted. In the first place, LED projectors feature warm color temperatures (2,700ºK to 3,000ºK), cold temperatures (5,600ºK to 6,500ºK), adjustable temperatures (2,700ºK to 6,500ºK and even bigger ranges), and RGBAW, with the possibility of achieving any color.

If the aim is integrating a new set without any existing items, the best solution would be using bluish light, cold projectors, from 5,600ºK to 6,500ºK, because these projectors have a lighting performance (candles issued versus watts consumed) up to 10% higher than warm-light projectors. Furthermore, pureness of color spectrum is better, typically by 2-3% as compared to warm-light units. However, if the studio has existing projectors and gradual replacement is envisaged due to budget constraints, either use warm-light projectors equaling the temperature of halogen lighting or, alternatively, use warm-cold adjustable projectors, which are more expensive and much less efficient, as candle luminance may be even one half of the luminance achieved per watt when compared to fixed-temperature projectors.

Additionally, LED Fresnel projectors feature a poorer zoom range as compared to halogen ones, especially in the spot position.  Quite the opposite, LED panels may have different beams from 15º up to 120º by using progressive diffusers. For older softlight types, a typical beam would be only 120º.

Last, another technical issue worth noting is color pureness of LED projectors, that is, spectrum quality, which we know is discontinuous as compared to halogen spectrum –nearly continuous. This means that light generated is not found in all frequencies, but only in a number of them (peak), while failing in other frequencies (off-peak). Traditionally, pureness used to be measured through the CRI (Color Rendering Index), which determines an average level by adding the relevant peaks corresponding to the 8 primary colors taking into account that a CRI of 95 was an acceptable value for light pureness (both for fluorescent and for LED lights).

But at present, TLCI (Television Lighting Consistency Index) is gaining ground. This measurement determines the average level of 24 colors, including pastel shades, flesh color, etc. A reasonable TLCI is regarded to exceed 90% pureness, equivalent to 95% CRI, but much more accurate.

However, in view that this is an average value, it does not guarantee that color will be the same as in other projectors that render an identical index. Compatibility test must be performed, most especially when lighting faces.

Taking into account all these issues, lighting now very much resembles traditional ways but with the enormous advantages offered by minimal consumption (typically 1:7, save for adjustable-color projectors that are at about 1:4 as compared to equivalent halogen lighting), insignificant heat radiated to the scene and nearly zero maintenance.

Last, let us introduce the notion of operating light through effects projectors. In former times, effect projectors were used to create effects, that is an spectacle, most especially in music shows, big contests, etc.

However, nowadays they are being increasingly used as substitutes for conventional projectors, mostly for dynamic programs such as reality shows, magazines, etc., in which the number of guests, their distribution, a combination of sets –including musical performances- make up a very diverse scene. In this case, setting up lighting featuring adjustment of movements is worthwhile as compared to several lighting ensembles for which in many instances there is no grid space.

Furthermore, with older mobile halogen-lamp or xenon-discharge projectors, maintenance was a parameter to consider, which is not the case with zero maintenance, robotic LED projectors.