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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 03 Jan 2008 (Thursday) 21:44
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The amazing speed of optical slaves

 
elwood58
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Jan 20, 2008 18:07 as a reply to  @ post 4743670 |  #61

PacAce,

I wonder what your neighbors think, or was this in a remote studio. I had one of the neighbors stop by my place when I was testing the studio lights, meter and camera to get a feel for over/under exposure in manual. My test scenario included 40+ shots, not rapid fire mind you. I guess they thought there was a down electrical line in my living room.

Actually I think they were just morbidly curious about what the geek next door was up to this time!


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PacAce
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Jan 20, 2008 18:17 |  #62

elwood58 wrote in post #4744490 (external link)
PacAce,

I wonder what your neighbors think, or was this in a remote studio. I had one of the neighbors stop by my place when I was testing the studio lights, meter and camera to get a feel for over/under exposure in manual. My test scenario included 40+ shots, not rapid fire mind you. I guess they thought there was a down electrical line in my living room.

Actually I think they were just morbidly curious about what the geek next door was up to this time!

Fortunately, it's winter and I have all my curtains drawn to help keep the heat in. So I doubt my neighbors would notice the 10 fps bursts of flash going on in my study. Beside, I'm fortunate to live in a neighborhood where my nextdoor neighbors are not nosey. :lol:


...Leo

  
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oldfella
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Jun 17, 2009 02:38 |  #63

mbellot wrote in post #4627915 (external link)
Probably just simply that the flash recharge couldn't keep up.

1/128 is 2^7 or 8 "stops" (2^0 = 1 or full power) difference in power level. During the 9 shot burst the flash would have had to manage to recharge at least 1/8 power (possibly more) to actually have sufficient juice for the 9th frame.

No flashgun could keep up. All you are doing is slowly discharging your storage capicitor. This can only be achieved by using 1/8 to 1/32 power. I find hammerhead flashguns the best for this.




  
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oldfella
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Jun 17, 2009 07:33 |  #64

Curtis N wrote in post #4626256 (external link)
Maybe no surprise to you smart people, but for those of us whose entire knowledge of electronics could fit on a postage stamp, it's pretty darned amazing. :cool:

Looking at your formulas, the HF does not make to much sense. The HF = f^2/(a*CofC)/1000. The 1000 is to convert the calculation to meters. You omitted to enclose a * c.




  
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mosesport
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Oct 02, 2009 12:06 |  #65

I'm very new to flash photography. Still don't quite have enough for my 580ex, but soon. My question seems dumb to me, and it may be, but here goes.

Can you use optical slaves in an environment like a club, or would the club lights makes the flash fire? Let the noob hazing begin. 0_o


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Curtis ­ N
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Oct 02, 2009 18:04 |  #66

What kinda club?

A golf club? Probably not. Optical slaves don't work well outdoors.

A card club? Sure. Indoors they're pretty reliable unless you're in some huge space like a gym. The big drawback to optical slaves is that anyone's flash will set them off. If there are other people there with cameras, it can be a problem.

If you're in a kind of club that uses strobe lighting, those things will definitely trigger optical slaves.


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buurin
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Oct 02, 2009 18:18 |  #67

FlashZebra wrote in post #4626382 (external link)
I have said this before, but optical slaves are my primary mode of triggering all of my flash units except one. That "one" typically has a long cord, or a radio slave.

I only use something else when the use of the optical slave just does not work in that application. But, since I mostly do studio, or ad hoc studio work, I seldom need to use anything other that optical slaves.

In addition to being fast, they are:
  • very inexpensive
  • require no batteries
  • typically do not wear out (I have some that I still use that are decades old)
  • Are almost indestructible (I mostly have the units that are the simple circuits totally encased in resin). You could drive a car over them and they would typically still be fine.
  • Did I mention they do not require batteries.
Enjoy! Lon

Do you shoot outdoors? Hows optical perform for you then?

I've never used my opticals.


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MDJAK
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Oct 02, 2009 19:31 |  #68

PacAce wrote in post #4626188 (external link)
No surprise there, Curtis, since the optical slave is working at the speed of light and there's not much to the circuitry--just a photo-sensitive transistor and an SCR semiconductor switch or equivalent, both also working at the speed of light. :)

On the other hand, a digital triggering circuit needs to convert the "fire" signal into digital code which is transmitted in series by the Tx and then received by the Rx, decoded and then converted to a signal that triggers the triggering circuit. That serial conversion before transmission and then after reception is what's slowing the RF triggering devices. Actually, the same applies to the ETTL IR signals, too. :)

But, sir, is not the awesome speed of light measured in a vacuum? So while it may not be much of a difference, in the real world light does not travel 186,000 miles per second, does it?

me




  
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cccc
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Oct 02, 2009 19:42 |  #69

MDJAK wrote in post #8750330 (external link)
But, sir, is not the awesome speed of light measured in a vacuum? So while it may not be much of a difference, in the real world light does not travel 186,000 miles per second, does it?

me

it only changes by a factor of 1.01 in air I believe...

when we are talking about 300,000,000 meters per second, divide that by 1.01 and it is still really fast... i promise.




  
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mosesport
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Oct 02, 2009 20:37 |  #70

Curtis N wrote in post #8749813 (external link)
What kinda club?

A golf club? Probably not. Optical slaves don't work well outdoors.

A card club? Sure. Indoors they're pretty reliable unless you're in some huge space like a gym. The big drawback to optical slaves is that anyone's flash will set them off. If there are other people there with cameras, it can be a problem.

If you're in a kind of club that uses strobe lighting, those things will definitely trigger optical slaves.

Yes, sorry. I should have specified. I meant night club, dance club, whatever you want to call it. Thanks for the tip :)


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bieber
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Oct 03, 2009 08:13 |  #71

buurin wrote in post #8749915 (external link)
Do you shoot outdoors? Hows optical perform for you then?

I've never used my opticals.

I actually have pretty good luck firing my SB-26 optically outdoors. I've been using it for something like two years now, and I still haven't gotten around to buying a third PocketWizard because I can just about always get the optical slave to pickup. It does cause problems occasionally, though, and if you'd like to have an accent light placed well out of frame, you could be in trouble (in that case, I'll usually pull it off by putting the PW on the out-of-sight light and having it fire the main light optically).


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PacAce
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Oct 03, 2009 09:58 |  #72

MDJAK wrote in post #8750330 (external link)
But, sir, is not the awesome speed of light measured in a vacuum? So while it may not be much of a difference, in the real world light does not travel 186,000 miles per second, does it?

me

Mark, Mark, Mark. If you can tell the difference between the speed of light traveling in a vacuum and light traveling through air or any other substance in the "real" world, then you're one heck of a man (a lot more than you are now, that is)! ;) :lol: :D :)


...Leo

  
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The amazing speed of optical slaves
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