In the production of an event, artistic intentions may raise several technical challenges such as the location of the audience, participants, cameras, projection surfaces, furniture, and their configurations in the capture space. To address these issues, the technical team must establish good communication with the artistic team from the start. Based on the artistic team’s needs expressed in a technical rider, the technical team must then confirm that the space being used can adequately meet those needs.
Space criteria should be considered based on the project type. For example, what are the stage dimensions? Is adding runways necessary? Should the telematics control room be located in a specific place? Is the physical placement of projection surfaces, lighting, and cameras based on their field of capture feasible? Does the project require additional accessories or furniture?
These questions will have a major influence on the required space and its configuration. Another equally important criterion is the maximum seating capacity of the venue, depending on the preferred format. For example, if you want great mobility for participants or the public, it may be preferable to opt for a more open space, or even to locate the audience on the floor, on the same level as the participants. Finally, depending on the expected attendance, the chosen space must of course be able to accommodate that number in a secure manner.
Location of audience and participants affects placement of equipment, such as the distance between cameras, projectors and video/telematics control room. This determines the type of connection needed (HDMI, coaxial, Ethernet, etc.) and if adapters or video signal converters are required, as different connections have varying ranges.
For example, with an HDMI 2.0 type cable, which supports a resolution of up to 4K, it is not recommended to have a connection of more than 10 m distance. Connections using the SDI standard, generally made up of a coaxial type cable and BNC connectors, are preferred for professional use. They make it possible to travel much greater distances than an HDMI link, ranging from 25 m to more than 200 m, depending on the quality of the cabling and the resolution of the video signal transmitted.
Although there are a very large number of possibilities, the following table presents some common examples for different types of links, as an indication:
| Type of link | Transmission rate | Maximum distance |
|---|---|---|
| HDMI 2.0 | 18 Gbps | About 10 meters |
| 3G-SDI | Up to 12 Gbps | From 25 to 100 m, depending of the quality of the cable |
| USB 2.0 | 480 Mbps | ±4.5m(passive); ±25 m (passive + active extension); ±29m (active); from 60 to 100 m (Ethernet extension) |
| USB 3.0 | ±5 Gbps (1st gen.); 10Gbps (2nd Gen); 20 Gbps (2nd Gen. x2) | ±3m (passive); ±15m (passive + active extension); ±18m (active); from 60 to 100 m (Ethernet extension) |
| USB 4.0 | 40 Gbps | ±0.8m (passive); ±3m (active) |
| Ethernet (Cat 6A) | 1 Gbps to 10 Gbps | 100 m |
| MIDI (DIN) | ±4 Kbps per directions | De 6 à 15 m, depending of the quality of the cable |
Note that a USB 3.0 or 4.0 speed is only effective when the link is of the end-to-end USB 3.0 type. For example, a set of USB 2.0 type links passing through a hub connected to a computer in USB 3.0, will not obtain a higher transmission rate than USB 2.0 – inside the hub, USB 2.0 flows generally travel on a parallel USB 2.0 bus and not on the USB 3.0 bus.
If certain signals come from or pass through other devices (an artist’s computer, MIDI controller, etc.) located at a location far from the telematics control room, it is important to ensure that the type of connection allows for proper signal transmission. Otherwise, an alternative connection would have to be provided. For example, if you want to transmit MIDI data from the telematics control room to a remote computer or controller (and vice versa) and the distance between them exceeds 6 m – or even 15 m for high quality cables – it would then be preferable to opt for a network transmission mode, such as OSC or RTP-MIDI, transmitted by Ethernet cable, or wireless (Bluetooth or Wi-Fi). In all cases, the needs in terms of adapters, converters or extensions necessary for the proper functioning of the connections between the equipment must be foreseen.
There are several types of lighting, and in a telepresence context their choice will be mainly determined according to the subject of the video recording, the location of the projection surfaces and, to a lesser extent, the presence of the public. On the other hand, certain types of lighting are more effective at close range, while others work better when they are further away:
Tungsten or halogen:
This type of lamp produces an orange-yellow light, but color filters can be added depending on the desired result. However, these lamps give off a lot of heat. For this reason, it is best to wear thick gloves when adjusting them and to keep them relatively far from the subjects;
HMI :
This type of lighting projects a continuous and balanced light, similar to that of natural daylight, providing sharpness and relief without too much contrast;
Fluorescent :
Just like tungsten lamps, you can add color filters. Unlike the latter, they emit little heat, and are lighter and therefore more practical. Their light being uniform and diffuse, they are generally placed closer to the subjects;
LED :
Like fluorescent lamps, this type of lighting gives off little heat and consumes less energy than tungsten lamps. You can also add color filters and change their light intensity. However, the rendering tends to look artificial, like interior lighting.
| Types of lighting | Benefits | Restrictions |
|---|---|---|
| Tungsten or halogen | Added color filters; adjustable light intensity; inexpensive | Yellow-orange light; gives off a lot of heat = away from subjects; low efficiency (10 to 30 lm/W) |
| HMI | Natural light; inexpensive; good efficiency (80 to 120 lm/W) | Requires UV protection glass; limited lifespan (~1000 hours) |
| Fluorescent | Added color filters; gives off little heat; uniform light; adjustable light intensity; inexpensive; good efficiency (80 to 115 lm/W) | Diffused light (360° illumination) = close to subjects; bulkier than LEDs |
| LED | Added color filters; gives off little heat; energy efficient; adjustable light intensity; high luminance; excellent efficiency (150 to 215 lm/W) | Artificial light; more expensive |
For an indoor video capture, three-point lighting is the most commonly used strategy. It consists of placing at least three light sources pointed towards the video capture area: the key light is usually placed at an angle of 45° in relation to the axis of the camera, located high up and slightly inclined, and must also have a higher light intensity than the other two sources; the secondary (or fill) light is used to reduce the shading effect, possibly caused by the key light. It will have a lower light intensity than the main source and will be placed at an angle of approximately 45° on the other side of the camera axis; the rear light is used to detach the subject(s) from the background. Its angle of radiation is not as important as the others, but it must still be taken into account if the space is captured by more than one camera.
The presence of a test subject that can move within the sensing field will make it easier to adjust the position, angle, intensity or effect of each light. To obtain more diffused lighting, the light can be directed more towards a white wall or background. If this is not possible, the use of a dichroic filter – translucent filter or reflector, white or of variable color according to the desired atmosphere – placed in the projector is ideal.
Always be sure to pay particular attention to reflections of all kinds (glasses, shiny objects, etc.), either by moving or slightly raising the headlights.
Finally, it must be ensured that any projector is placed in a safe place and is not an obstacle to the proper movement of the subjects or the view of the public, if necessary.