Pete Askew
Admin
A conversation recently made me realise that, although I often refer to a light source being driven by a generator, some people had not seen one and couldn't work out what I meant. I will produce a more extensive write-up on these lighting systems but for now, here is a quick illustration of a classic generator system. More modern units have finer controls in some cases and LCD displays etc but these old Bowens units are incredibly reliable, accurate and reproducible and easy to service. I did toy with the idea of updating them a couple of years ago but I have so many light modifiers etc for the old L-System that it just wasn't worth it.
Unlike speed-lights and flash mono blocks, a generator system produces the high voltage needed in a large pack and distributes that to the heads containing the flash tubes. The advantage is that you can position the pack in a more convenient position and potentially have (in these examples) 4 heads controlled by a single generator. The disadvantage is the heavy leads that carry the high voltage but that is fairly minor and a lot easier than having to use a step ladder to adjust the power output on an overhead light! (OK, some modern systems have remote controls).
Generators (or packs) come in two basic varieties, either symmetric or asymmetric (the ones below are asymmetric but I have symmetric ones as well that are useful for ring flash etc). The difference is that with a symmetric generator all of the outputs / heads receive the same voltage and hence the flash heads produce an equal amount of light. With an asymmetric generator you can adjust the output of the individual outlets and, as you can see from the example below, the 4 connectors have 'native' outputs of 250, 750, 1500 and 500 Ws (watt seconds or joules if you prefer). You can adjust the total output from 3KJ to 750 KJ using the stepped controller labelled 'Flash'. You can also add the outputs together using the +/- sliders next to the outlets (in the top generator, the full output of the pack has been directed to the righthand outlet and is thus receiving a quarter of the total pack output - 750 J). The other thing that the generator controls is the modelling light of each head. This can be adjusted in overall intensity (the Modelling knob), but is proportional to the output that the head is receiving. It can be turned off, left on permanently or can be turned off when the flash fires and back on again when the capacitors are fully re-charged (this speeds up recycling times). There is an audio signal that tells you when the pack is ready and this can be switched off (Audio switch). Above the power switch there is also a tortoise and hare recycle speed switch. As you can imagine, the hare recharges faster than the tortoise, but is harsher on the capacitors. There are various cut-outs and a warning lamp to the right of the mains switch along with a reset button.
The generator is connected to the camera using either a sync lead (as in this case) or a radio / IR trigger. You can also fire the pack using a photocell such that when one flash fires the pack will fire also. This is controlled by the photocell (to the left of the Flash dial) and selected with the switch beside it. The flash-ready lights surround the Flash dial and are green when the pack is ready to fire. If you decrease the output after it has charged this light will blink and you will need to discharge the pack using the Open button next to the dial or you will over-expose your image (the capacitors still have the original charge). You will notice in the image below that I have two sync leads attached. One is going to the camera (actually a PhaseOne back at the moment) and the other is connected to a light meter (image 2). This is very convenient as I can trigger the flash from the meter while taking a reading without having to remove the lead from the camera (and then forgetting to put it back on!).
The last image shows a typical head (in this case the one I used to shoot the wood that had been attacked by termites). You can see the heavy lead that attaches it to the pack (about 3m away) and the honeycomb box I was using as a light modifier. It is attached to a Manfrotto Autopole via an adjustable clamp arm. The only control on the head is an on/off switch which turns off the modelling lamp (to keep it cooler and extend its life - although the modern halogen bulbs are much longer-lived than the old photofloods!). The head also contains a cooling fan.
A range of heads can be used with packs and these come in a variety of power ratings. You can use higher-rated (they go up to 6KJ) ones with a lower output pack but you must take care when using lower-rated ones with a higher output pack if you don't want to blow the flash tube. The tubes can be replaced but are quite pricey. All components can be serviced. Heads come as standard heads as shown here and can be fitted with a wide range of modifiers from simple dishes to soft-boexes etc. There are also linear heads with long straight tubes rather than circular ones, focusing spots, a thin candle head and a ring flash. The heads can be mounted on stands, poles, boom-arms and on overhead pantographs and rails. The systems (from whichever manufacturer) are extensive.
Unlike speed-lights and flash mono blocks, a generator system produces the high voltage needed in a large pack and distributes that to the heads containing the flash tubes. The advantage is that you can position the pack in a more convenient position and potentially have (in these examples) 4 heads controlled by a single generator. The disadvantage is the heavy leads that carry the high voltage but that is fairly minor and a lot easier than having to use a step ladder to adjust the power output on an overhead light! (OK, some modern systems have remote controls).
Generators (or packs) come in two basic varieties, either symmetric or asymmetric (the ones below are asymmetric but I have symmetric ones as well that are useful for ring flash etc). The difference is that with a symmetric generator all of the outputs / heads receive the same voltage and hence the flash heads produce an equal amount of light. With an asymmetric generator you can adjust the output of the individual outlets and, as you can see from the example below, the 4 connectors have 'native' outputs of 250, 750, 1500 and 500 Ws (watt seconds or joules if you prefer). You can adjust the total output from 3KJ to 750 KJ using the stepped controller labelled 'Flash'. You can also add the outputs together using the +/- sliders next to the outlets (in the top generator, the full output of the pack has been directed to the righthand outlet and is thus receiving a quarter of the total pack output - 750 J). The other thing that the generator controls is the modelling light of each head. This can be adjusted in overall intensity (the Modelling knob), but is proportional to the output that the head is receiving. It can be turned off, left on permanently or can be turned off when the flash fires and back on again when the capacitors are fully re-charged (this speeds up recycling times). There is an audio signal that tells you when the pack is ready and this can be switched off (Audio switch). Above the power switch there is also a tortoise and hare recycle speed switch. As you can imagine, the hare recharges faster than the tortoise, but is harsher on the capacitors. There are various cut-outs and a warning lamp to the right of the mains switch along with a reset button.
The generator is connected to the camera using either a sync lead (as in this case) or a radio / IR trigger. You can also fire the pack using a photocell such that when one flash fires the pack will fire also. This is controlled by the photocell (to the left of the Flash dial) and selected with the switch beside it. The flash-ready lights surround the Flash dial and are green when the pack is ready to fire. If you decrease the output after it has charged this light will blink and you will need to discharge the pack using the Open button next to the dial or you will over-expose your image (the capacitors still have the original charge). You will notice in the image below that I have two sync leads attached. One is going to the camera (actually a PhaseOne back at the moment) and the other is connected to a light meter (image 2). This is very convenient as I can trigger the flash from the meter while taking a reading without having to remove the lead from the camera (and then forgetting to put it back on!).
The last image shows a typical head (in this case the one I used to shoot the wood that had been attacked by termites). You can see the heavy lead that attaches it to the pack (about 3m away) and the honeycomb box I was using as a light modifier. It is attached to a Manfrotto Autopole via an adjustable clamp arm. The only control on the head is an on/off switch which turns off the modelling lamp (to keep it cooler and extend its life - although the modern halogen bulbs are much longer-lived than the old photofloods!). The head also contains a cooling fan.
A range of heads can be used with packs and these come in a variety of power ratings. You can use higher-rated (they go up to 6KJ) ones with a lower output pack but you must take care when using lower-rated ones with a higher output pack if you don't want to blow the flash tube. The tubes can be replaced but are quite pricey. All components can be serviced. Heads come as standard heads as shown here and can be fitted with a wide range of modifiers from simple dishes to soft-boexes etc. There are also linear heads with long straight tubes rather than circular ones, focusing spots, a thin candle head and a ring flash. The heads can be mounted on stands, poles, boom-arms and on overhead pantographs and rails. The systems (from whichever manufacturer) are extensive.
