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Multiple Flash

By Jock Orr.

The first part of this article appeared in the March issue of the Belfry Bulletin where it described the assembly of the flash control box, with flash units, cables, etc.

To continue refer back to p.26 (and circuit diagram) of March B.B. Assuming that somebody has now completed the assembly and wants to know how the contraption works.

Testing The Control Box

ONE FLASH:  Move switches A. B. & C. to UP position.  Plug in cable to socket No.1 and the other end into flash unit. Insert plug to bridge socket 2 & 3. Plug in camera contact cable OR manual firing cable to firing socket.  Press SW.1 to check the circuit and L.1 should light up to indicate circuit is O.K.  Fire PF.1 bulb from (camera or manually).

TWO FLASH:  Follow the above procedure, but this time plug in cables to sockets 1 & 2. Bridge socket 3.  For THREE FLASH – plug in cables to sockets 1. 2. & 3.

FOUR FLASH:  Move switches A. B. & C. to DOWN position.  Plug in cables to any four sockets.  Bridge remaining sockets.  Press SW.2 to check circuits and L. 2 should light up to indicate circuit is O.K. Test fire four more bulbs.

FIVE – SIX FLASH:  Follow the above procedure.  Plug in cables as required.  Bridge remaining socket if using five flash.  Fire off another or six flashes and hang the expense because you know the thing actually works.  If it doesn’t work then something is wrong!  Check everything and start all over again.

WARNING:  Six flash bulbs fired simultaneously in a confined space generates a fair amount of light – take care of your eyes.

NOTE: You can fire any number of flash bulbs from one to six with the switches in the down position.  Remember to bridge the empty sockets.  BUT! When firing only one or two flashes on the switches in the down position your camera contacts will be carrying a heavy jolt of current from the large capacitor at a pressure of 45 volts.  So use the down position for one to three flashes on extended cable runs only, where you need the extra voltage to push the current through the cable resistance.

Suitable cable is ordinary twin domestic flex in a pliable plastic outer covering as used for table lights and such like small appliances.  Anything thinner than this becomes difficult to untangle.

Use the small layer-type battery to power the Control Box.  They are compact, high voltage batteries with a mere trickle of current output.  The capacitor stores the trickle of current and releases it in a pulse of energy which is pushed through the cable by the voltage pressure.

A point of interest is that the ordinary battery – capacitor flash gun requires a pulse of 2 amps of current and a minimum of 4½ volts to fire a PF.1 bulb.  A parallel-wired device to fire six flash bulbs would consume approximately 12 amps of current, still at 4½ volts, resulting in a very rapid discharge of the battery.

The advantages of series wiring, which is what we are concerned with in this multi flash outfit, is that the current required for six flash bulbs is no greater than for a single bulb, although the voltage increases proportionally to the number of bulbs used.  The voltage of the batteries used in this particular circuit is adequate even when part discharged and the small demand on current will allow the batteries quite a long time of usage before they are due for renewal.

Using The Multi Flash

Harkening back to page 26 of the March B.B. again, lets take another look at the illustrations.  So far the 6 cables 7yds. long have been plugged in with the flash units and tested.  The “wire 3 off plugs as shown” are of course the bridging plugs.  This leaves the mysterious “wire 5 off each socket as shown” and the “3 cables 14yds. long” to explain away.

The 14yd. cables are simple extension cables for long runs where required, and the sockets are used to make up the joins in cable layouts for any particular lighting arrangement.

A look at the illustrations accompanying this issue of the B.B. will reveal five fearsome – type cable joins. But when you have it all figured out they only take a matter of seconds to connect up.  They are in fact a simple system which enables the photographer’s assistant to adapt the cable runs to suit any situation.  After hours of practice on the surface, that is.

Anyway, to get on with it. Have a look at figure ‘F’.  It represents the Control Box with four cables plugged in and two bridges.  The heavy lines denote the circuit inside the Control Box feeding the cable sockets. The point of the illustration is to show that the circuit is a CONTINUOUS LOOP, and this is the point to bear in mind every time you make a join with the patent sockets.  Figures’ A’ & ‘B’ are straight-through cable connections.

 

Fig. C

Figure ‘C’ is a cable join with a flash unit directly off it.  Figure ‘D’ can be used in two ways: - a cable join with two spurs, or a cable termination in three spurs to take three flash units.  Figure ‘E’ can either be a cable join with spur to one flash, or a cable termination in two spurs.  This by no means completes the combinations.  The rest you can work out for yourselves.

The sketch (Fig ‘F’) shows a typical lighting arrangement using six flashes.  Naturally cables should be hidden from view.

                                                                                                                                       Spur to Two flash

Fig. E                                                               Fig. D

FiGURE F.

FIGURE G.

The sketch (Fig ‘G’) is somewhat compressed to scale, but this is the sort of layout for photographing a long way into a cave passage of some similar situation.  Caverns and pots can get the same lit-up treatment. Obviously, in place of the usual flat effect, you are now going to get a sense of modelling and perspective which will enhance your pictures no end and please you enormously.  Apply standard indoor flash techniques and guide numbers as recommended in booklets on the subject and you won’t go far wrong.  Good Luck.  Especially with the action shots.

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The hut warden has decided that all crockery and cooking utensils will be removed from the belfry on week ending 10th. August 1968 until further notice…………………bring your own!