Return regularly and ‘refresh’ for the latest version. If you are considering changing to LED lighting have a glance at this page:-LED

Anyway here’s some ‘light reading’!

STAGE LIGHTING
Generic stage lighting (individual units are known as lanterns.. (never lamps. (they are the glass things that go inside the lanterns.. bulbs go in the ground and grow into flowers)) uses 4 basic types.
FLOODS, FRESNELS, PROFILES & BEAMLIGHTS. Each of these basic types is available in a variety of wattages (power) of which 500W and 1000W (1KW) are the most often used in small venues.
There are many different manufacturers world-wide but within the basic types all brands are very similar – choice of manufacturer being largely a matter of personal taste.

FLOODS:
The most basic lantern, just a lamp in a box, they are used as wide angle “floods” of light on scenery and backcloths. We use them for illuminating the music of musicians in big orchestral and choral performances and sometimes (rather unconventionally) as a means of putting colour onto stages where resources are very limited and LED technology hasn’t yet arrived.

FRESNELS:
Lanterns with a fresnel lens provide a soft light. The fresnel lens has a series of concentric rings in ‘steps’ on it. There is (invariably) a means of moving the lamp in relation to the lens. The nearer the lamp is to the lens the wider the beamspread and vice versa. “Barndoors” (hinged flaps) can be added to roughly shape & crop the beam of light.

PROFILES:
Lanterns with a profile lens (it looks like a magnifying glass) will project a sharp focused beam of light. There will be a ‘gate’ assembly between the lamp and the lens, with shutters to shape the beam. “Gobos” (metal plates with cut out patterns) can be inserted in the gate to project quite complex images. Followspots (a kind of profile) usually used to highlight solo performers in musical or variety shows, will have an iris in the gate to vary the diameter of the (circular) beam produced.
NB a variant of the profile.. well a sort of cross between it and a fresnel.. is also produced – called a PC (pebble convex)

BEAMLIGHTS:
Lanterns similar to floods (they have no lens) but (usually) taking a sealed beam lamp like a car headlamp that gives an intense, fixed spread, light. Usually now the ‘PAR’ range of lanterns, eg. PAR64, PAR56 etc. The number refers to the diameter of the lamp in eights of an inch so PAR64 is 8″ diameter. Much used in the music industry.

THE VARIABLES
There are three basic variables open to the stage lighting designer.

Position: which dictates the direction from which the light strikes the stage. (in amateur theatre the position is frequently limited by the available hanging positions)

Colour: The range of colour available to the modern lighting designer is as wide as the visible spectrum.  Be bold, experiment with colour. In principle you can light naturally (using the sorts of colours seen in the real world, and trying to re-create that world on the stage) or using vivid, mood provoking colours. This latter option is usually limited to musicals and variety shows. LED technology has introduced the possibility of varying colour during scenes, see ‘LED’ below.

Intensity:
Each lantern, or group of lanterns, is connected to a dimmer circuit, enabling the designer to balance the overall effect of the lit stage (as well as allowing the light to be faded up or down at a rate suitable for the show.)
In the old days dimmers were ‘resistance’ devices, (originally a tube full of water (caustic soda actually) but in later years, and up to about the 1960’s, a series of wire wound resistances with some form of wiper blade making contact with them.)

Since the 1970’s almost all lighting control has been by electronic dimmer units, which not only remove the risks associated with dimming via live wires, but also allow for remote control.

The electronic dimmer works from one of two commonly accepted controls. Analogue control voltage is the older: the desk sends a signal down a separate bit of wire for each dimmer. This signal voltage will be 0V when the lamp is intended to be out/off, and +10V when it is intended to be full/on (+5V will give you about 1/2 brightness etc.) The exception to this basic, worldwide accepted, system is the arrangement used by Strand Electric for many years where -10V gives you full on!!! (yes we know it was stupid, but Strand would never admit it) Be wary of this, if you are still using analogue control, because many Strand desks won’t drive other manufacturers’ dimmer racks and vice versa, and in some cases unfortunate damage occurs.

The other control method, now universally accepted, is DMX. There’s a page about DMX on this site which you might like to look at, but for the moment…..

DMX control operates on a stream of digital pulses which carry all the control information for all the dimmers, and much else, down one pair of wires. Each dimmer (or gadget) is given its own ‘address’ (between 1 and 512 usually) and only responds to the information coming down the line addressed to it.

These various methods allow you to fade your lanterns up and down. Generally small and older systems (12 ways or so) will work from analogue control, while newer and more complex systems will work from DMX, introducing many more facilities.

The first objective is, of course to enable you to set different levels for each lantern in your rig. If you are using a manual desk you will need to establish a method of writing down the level for each lantern (channel) for each cue. The most commonly used methods are a grid of numbered squares, one square for each channel. In the relevant square you write the level for the particular cue you are noting at the time (1 – 10…although 10 (full) is usually noted as ‘F’) unused channels in a particular cue are left blank. If you are caught on the hop and haven’t got a grid made out the usual convention, that most people will easily follow, is to write in longhand:
the channel number followed by a comma followed by the level in brackets. Thus 17,(5) 18,19,20, (F) means channel 17 at point 5 (half) and channels 18, 19 and 20 at full.

With manual desks it is often useful to arrange to cluster associated circuits together. For example if you have a batch of channels running blue lights on a musical show it may help to plug them to adjacent channels of the control system.
This means that when you want all the blue lights together you only have to fade up a group of adjacent circuits….rather than grabbing for, say channels 2, 14, 16, 19 and 23. (Try finding those in a hurry in the semi darkness with one hand!!) Naturally the use of a simple memory desk does away with all these hassles.

Several different methods of inputting and recalling information into and from memory systems have been tried in the past 30 or 40 years. Obviously the actual technology has moved forward…I was offered a punch card operated desk for sale in the seventies!… but the bit that matters to you and I is how the desk understands and interprets what you want it to do.

Early desks frequently used a keypad (or keypads) on which you entered ‘channel 26 @ point 7’ etc before allocating the lighting state a memory number and recording the memory. This system was used for many years, reaching its best quality and user friendliness with (arguably) the Thorn QT desk as early as the seventies. But the world moved on, and manufacturers like Zero 88 produced ‘live style’ desks which incorporated actual faders (like a preset manual desk) so the operator could actually feel the fader and provided the means to record the output of these faders as a state. At the best desks like this allow the operator to recall states / memories back into group faders that can also be mixed together live during the show. Zero 88’s ‘Jester’ is a small scale memory desk (there are many) which allows both group fader operation, and ‘cue stack’ where a one button push will advance the lighting to the next cue as the show runs. Acually, in practice, few amateur shows run long enough (enough performances) for stack operation to be 100% advisable as it isn’t too easy to correct for performance vagueries with that method.

Most common among the old desks of this size was probably Sirius, which found its way into almost every school drama studio up and down the country. Sirius recorded and churned out states (via a go button) but, despite having a small group fader section, was a bit lacking in flexibility for live musical show or concert use. It was however a solidly reliable workhorse for small scale straight play performances (you probably had one at school).

Latterly PC based programs, and some ‘apps’ are becoming common. Most require some form of dongle that will convert the USB output of the PC to the DMX convention, and most manufacturers will have arranged it so that their ‘dongle’ alone can be used with their program. (This is to ensure you pay them something, because the programs are frequently freely avaialble.) Some ‘open source’ programs will run via a number of different generic dongles.

Worst feature of all these on screen desks is that the mouse will only move one fader at a time… so while you might be used to grabbing a few faders for a cue you will now need to plot in such a way that each cue only requires the movement of one fader. This will tend to push you towards the ‘cue-stack’ (press ‘GO’) style of operation.

Let’s talk about colour. A couple of decades ago it became possible to arrange for the colour of the beam of light coming from a lantern to be produced using di-chroic filters, and (returning to an archaic technique) mixing the primary colours (red, blue and green……(yes that’s right, red blue and green..it works differently from paint colours!)).

Now the designer’s choice has been expanded by the introduction of LED lanterns working on the same principle of mixing red/blue/green. LED technology is still expensive by comparison to conventional incandescent lamps, (unless you are the electricity bill payer!) and gives much less light out. However there are some advantages in terms of heat, power consumption and the economy of not having to replace lamps. Be aware that although LED units produce blue and green quite well, the red is usually slightly less intense. Some manufacturers produce colour by mixing the ‘secondaries’ (Magenta, cyan and yellow) and some units now also include white (albeit frequently with the bluish tinge you have encountered in oncoming modern headlights!).  Each colour in your LED lantern.. and sometimes the overall level too .. will be controlled by a seperate channel of your DMX control. So a basic flood/wash light is going to use up a minimum of 4 channels of your desk.

Anyway the usual way of colouring the light from a lantern is to put a piece of filter (gel) in the colour frame in front of the beam. This filter will allow some of the light to pass through, and will absorb some of it. Naturally it gets very hot and has to be specially made for the job. It is very difficult to describe colour, (your idea of a peach colour, for example, will be different to mine). So the colours in the lighting filter ranges (and each manufacturer will have maybe 300 or 400 different colours and shades in their range, and there are several different manufacturers) are given numbers.

These numbers will seem to be a bit random at first glance. If you have been working in the business as long as I have you will be able to remember when the only readily available colour was Strand Cinemoid (or maybe Furse ‘Fursine’ which had the same numbering scheme) and the range consisted of a few dozen colours..These were numbered starting from a base range of just 30 colours (numbers 1 to 30) which followed a logical pattern.

Later additions came in batches and were thus easilly remembered. When competitors started producing colour they generally retained the basic numbers of the old Strand Cinemoid range, but added a number to it. So primary red in Cinemoid was number 6, but Lee called it 106, adding 100 to all the Strand numbers for their initial range. Obviously as the years have gone by different manufacturers have added their own colours and the number schemes have drifted further and further apart. You’ll find, as you use this sort of colour, that in the end you develop a few dozen ‘favourites’ and will readilly remember the numbers of those…whichever manufacturer you use.

IF YOU HAVE SPECIFIC QUESTIONS EMAIL ME AND I PROMISE TO GET BACK TO YOU PERSONALLY (usually within 48 hours unless we’re out on site somewhere running someone’s show!).

info@phosphene.co.uk

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