Why can't I dial the power for each individual head?

[todd_joseph]

I don't understand why most strobe units don't let you actually control the power for

each individual head. On the speedotron units for example there is a dial to control

all the power in a whole but not individually. Does this have to do with the way the

capacitors are arranged. Please explain this. Todd

[gary_woodard]

I don't think this is true.

[beepy]

Get a <a href="http://www.profoto-usa.com/products/d4/d4_why.asp">Profoto D4</a>

to control individual heads in a fine-grained way. I too find the standard power pack (liek

Speedotron) fractional/combine power distribution with an overall power dial to be

somewhat interesting... The Profoto-style seems a lot more straightforward.

<p>

Which doesn't answer your question as to why they do it the non-obvious (to me) way.

[todd_joseph]

funny, I was just looking at the D4. Too bad though it's just a tad out of my budget.

[ellis_vener_photography]

SOme Balcar Broncolor and Elinchrom packs have this level of control as well. There used

to be a company called Venca which made Speedotron Blackline head compatible packs

which had this feature. This was maybe 15-20 years ago. Without changing brands it

might be a good idea to get a second or third pack if you find yourself needing to do this

regularly

[Jochen_S]

My old Elinchrom Quantas offer no control at all. I suppose in the packs you are complaining about all heads are wired paralel to the capacitors. I have no idea what electrical element could be used as a dimmer in front of a heads plug. I could understand if packs wich offer single head control were devided internal to more than one logical pack, so the amount of capacitors for each head can be choosen.

[david_goldfarb]

While this sort of control is convenient, it's not absolutely necessary. You can move the lights closer or farther from the subject for finer adjustments than the pack permits.

[jeffrey_abelson]

"While this sort of control is convenient, it's not absolutely necessary. You can move the lights closer or farther from the subject for finer adjustments than the pack permits."

 

t6hat's not a great solution - as light is moved away it becomes a smaller source thus harder...

[kevinconnery]

<i>Does this have to do with the way the capacitors are arranged</i><p>

Yes.<p>

Until recently, large banks of capacitors were ganged together, and switched in/out of circuit. Thus, the older designs--which includes the current Speedotron packs, older Normans, older Photogenic FlashMaster, Novatron, etc--could only turn the pack up/down as a whole, while controlling head-specific output was either not available ("symmetrical") or by using different sockets in an assymetrical mode.<p>

The next step was per-channel power control, where (usually) two channels could be controlled somewhat independently, each channel being hardwired to (usually) either 50/50% or 33/66% kinds of splits.<p>

Some more modern designs for pack systems, like the Profoto D4 mentioned earlier, let the user control each light outlet from an overall pool of power. This is likely to be more common in the future, but it's not the norm yet, and it's still an expensive approach; there's some tricky electronics going on inside, especially if color temperature is to remain consistent for all lights.

[david_goldfarb]

While Jeffrey's point is true, that if you move the light closer or farther from the subject, you change the quality of the light, it's not that much of a problem in practice, as long as you've got the physical space to move things around.

 

On my old-style Norman pack, I can usually control the output of each head by increments of a stop or less using the controls on the pack and by moving the plugs from one side to the other, so moving a light a small increment to get a 1/3 stop or 1/2 stop adjustment doesn't usually change the character of the light too much. If the placement is really critical, ND gels are another option.