DMX

What is DMX?

A DMX, digital multiplex, is a standard protocol for stage lighting, e.g moving lights, LED’s. It was originally developed to allow stage lighting technicians to control a large number of lighting channels on the stage using a control desk that could be positioned away from the stage, without the need to run large lengths of mains electrical cable for each lighting channel. The DMX uses a small voltage control cable, which connects the lighting desk and dimmer packs. Each DMX link can control up to 512 channels. This is what makes a DMX universe.

DMX was first designed to adjust the brightness and intensity of each channel from 0 – 100%. The data which would be sent from the DMX cable for each channel is measured in bytes, which represents the brightness value. The dimmer pack will receive the values, which will then adjust the values to each light.

A decoder is built into the dimmer pack. The dimmer must be set onto the desired channel, (i.e 1 2 3 etc.) This will then allow you use that specific fixture. This is usually accomplished by using a DIP switch, or LED/LCD display. This desired channel is known as the DMX address.

Planning your addressing:

Before you start addressing your fixtures, you need to put the fixtures in a logical order. This will help you figure out which fixture is which later on. You need to find out how many channels it will take to use each fixture. In the theatre at Rotherham College, you will need 6 channels for each fixture. So the starting address will be on 1 and end on 6. The next fixture will start on 7 and end on 12, and so on until the 512 channels are used, or until a terminal plug is used to end the chain. Each channel will control a different light in an LED fixture, or control the movements of an Imove/Mac.

The LED fixtures will need a number of channels, as they have different coloured bulbs in them. In the studio theatre, each bar of LED Parcans is set to the same address. This is useful as if the lighting designer wanted red LED lights, they would just have to push the fader for that channel up. This would then turn on the red LED’s. It would be the same for the other colours that are available.

For the Imove and Mac’s, it would be the same procedure as the LED Parcans, only it would be for GOBO’s, pan, tilt, colour etc. Each effect will have their own channel, like the LED’s with different colours. Each Imove and Mac will be on their own address, as if they were on the same ones, the Imoves will go in the same direction of each other instead of opposite.

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Why do lanterns need cleaning?

As a Theatre is a place where a lot of dust is gathered. When dust gets hot it can ignite. Lanterns, by their very nature, produce a lot of heat. It is important for lanterns to remain as dust-free as possible to avoid fire. This is the reason why lanterns are regularly cleaned.

How to clean a lantern:

 

  • Firstly, clean off any excess dust, paying close attention to air vents, in which the dust may get clogged up.
  • Whilst working on the outside casing, check the cable and plug for any wear and tear. Examples of this are slits in the cable. The cord cable is the most common place that may become damaged.
  • Checking the plug can be by slightly moving the pins and, if it move rather vividly, the plug will need replacing, making the current one unusable.

 

 

  • Opening the casing is the next step to cleaning a lantern. Getting inside the lantern varies on the type of lantern. Often, a screw/catch is found to keep it shut.
  • Once inside the housing, remove the bulb, but carefully don’t touch it.
  • Using a sucking device, (such as a hoover,) start removing remaining dust/cobwebs.

 

  • Clean and polish the reflector. (spotting a reflector with spots on will not clean well.)
  • Use source4 cleaning liquid, as standard glass cleaners are unsuitable.

 

  • Check inside the lantern for any cables that may be shifting and splitting.
  • Check lamp holder and terminal blocks to make sure there is no burns, as that could be fatal.

 

  • Putting the lantern back together, means checking the reflector is safely in place.
  • Make sure shutter blades have no nicks on the edge.

 

  • Finally after cleaning and adjusting, a PAT test is to be undertaken. This entails both a visual and electrical test.

Health and Safety

What is Health and Safety?

Health and Safety,is used to ensure that the employer and employee can work in a safe and secure environment. Anywhere that this sign is shown, Health and Safety is taken seriously.

What are the regulations?

  • LOLER (Lifting Operations and lifting equipment regulations 1998)
  • Working at heights (2005)
  • Health and Safety at work act (1974)
  • Management of Health and Safety at work regulations (1999)
  • Electricity at work regulations (1989)

 

LOLER (Lifting Operations and Lifting Equipment Regulations)

These regulations require that lifting equipment, used on a day to day basis, must be checked annually. For theatre use, LOLER will be used for lifting/moving heavy objects, such as ladders, access towers and lanterns. This regulation states that after each item (if applicable) has been checked, a risk assessment form must be carried out then filled in and, handed in to the most competent person i.e supervisor/manager. The LOLER act covers equipment, such as, Lanterns, stage blocks and access towers.

 

Working at Heights (2005)

This act was put in place on 6th April 2005. It is there to ensure that people working above ground level can do so safely and with confidence. This regulation applies to all equipment and persons, working at heights. For Theatre, this is a good act, as technicians need to climb ladders/access towers, to reposition lanterns. The reason for this legislation is to prevent injury, as working at heights can be fatal.

 

Health and Safety at Work Act (1974)

This act puts into place, the duty of care upon both employer and employee. This gives the employer and employee the responsibility of making sure that, all persons in the work area, are using equipment safely and responsibly. This also includes self employed persons.

 

Management of Health and Safety at work regulations 1999

This act states that every employer should make a sufficient assessment of the safety of potential/current employees and what hazards they are exposed to whilst in the working area. A risk assessment should be documented and revised, for if there is any changes to the risk. These assessments must be checked annually.

 

Electricity at Work Regulations 1989

This law is obliged to carry out a programme of testing and checking maintenance. The testing should be carried out when:

  • Any electrical equipment is used by any employee
  • Where the public can use appliances (hospitals, schools etc.)
  • When electricals are hired

These laws are designed to improve safety of a public area and workplace.

Choosing Lighting Positions

Choosing Lighting Positions

One thing to always consider whilst creating a lighting plan, are the shadows that might be on show, which will make the performance seem less professional.

Lighting from the front:lighting-1

A vertical beam will be more efficient for lighting from the front, as the lit area of the stage and the shadows, shou
ld be no wider than the actor. One con of this is that the actors eyes will then be seen as black holes and the nose (which will be highlighted from the lantern) will then shade the mouth, making the facial features less noticeable.

 

When the lantern is moved slightly forward, it will start to reach the actors mouth and eyes (if the chin is being held upright in the right posture.) However, with the lantern being brought forward, shadows will be present. The shadow cast from the actor will go more upstage.

lighting-1

As the lighting comes more to the front, the actors facial features become more visible as they receive more light. Again, this increases the shadow which expands further and further upstage with the likelihood of the shadow hitting the scenery.

lighting-1

Enter a caption

 

As the lighting is right at the front of the stage, the actors features becomes too bright as well as the scenery. The shadows increase dramatically. When the lighting is like this, the beam shape goes horizontal, known as a corridor, which shows the entire depth of the stage, and the actors shadow becomes the same as the actors length.

lighting-1

 

 

Lighting from below projects the actor’s shadow, so it goes bigger when the actor is closer to the lantern. But when the actor moves further away, the shadow will decrease. When there is only this lighting angle, the light on the face reflects will soften the harsh features.

 

Lighting from the back and side:

Lighting from behind the actor does not help to illuminate the facial features. It helps by giving depth to the stage. This is done to separate the actor from the scenery. This is done by highlighting the head and shoulders. As this type of lighting does not land on the face, strong colours can be used.

When the light comes a little from the side, it will start to again, illuminate the face, on the side where the lantern is based. The shadow will cast alongside of the stage, in the opposite direction of the lantern.