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Strobe - Alexa Mini


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#1 James R Blann

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Posted 10 February 2016 - 04:07 PM

Hi all,

 

Apologies if this has been over-asked but I keep running into brick walls looking for answers.

Shooting strobes in the UK and looking for a solution that doesn't mean shooting on Epic with a motion mount. Any suggestions on strobe units or any things to look out for would be greatly appreciated! 

 

Cheers!


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#2 Phil Rhodes

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Posted 10 February 2016 - 04:09 PM

Such things do reputedly exist. I had to build one for a particularly key job. Couldn't find a rental.


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#3 Stuart Brereton

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Posted 10 February 2016 - 04:21 PM

Are you trying to sync the strobe to the shutter, or merely trying to avoid rolling shutter artefacts?


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#4 James R Blann

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Posted 10 February 2016 - 04:46 PM

Thanks guys.

I'm trying to avoid rolling shutter basically, may be shooting at frame rates up to 200fps also.


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#5 Stuart Brereton

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Posted 10 February 2016 - 05:08 PM

I've used the Lightning Strikes Paparrazi light in the past with zero rolling shutter issues. I'm told that the Atomic 3000 strobe can be set to have a flash duration long enough to avoid half-frames, but be advised you must have DMX control to do it.


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#6 Phil Rhodes

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Posted 10 February 2016 - 05:44 PM

Increased flash duration will not prevent tearing. The problem is caused by the fast rise and fall times, which, in order for the strobe to actually operate as a strobe, are necessary.

 

P


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#7 Stuart Brereton

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Posted 10 February 2016 - 07:37 PM

Increased flash duration will not prevent tearing. The problem is caused by the fast rise and fall times, which, in order for the strobe to actually operate as a strobe, are necessary.

 

P

 

The Paparazzi light works. Whether that is from increased duration or slower fall and rise times, I don't know, but we had zero issues with it.

 

I know of people who have used the Atomic 3000 with DMX and have had great results. YMMV


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#8 David Mullen ASC

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Posted 10 February 2016 - 07:56 PM

I haven't had problems with Paparazzi strobes and the Alexa.

 

With the Atomic strobes, what I've found is that you get a cycle where it falls into sync with the rolling shutter and then it drifts out and you start getting partial frames.  So when I used them on a scene in "Extant", I basically had to call "action" when I saw the strobing sync with the shutter and we'd get a minute or so before it drifted off again.


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#9 Stuart Brereton

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Posted 10 February 2016 - 08:17 PM

One issue I have found with shooting strobes (in this case with a Red Epic) was that even if we got the strobes in sync with the shutter, there would still be a huge slow moving rolling bar in the viewfinder, which eventually would black out the viewfinder for several seconds, making it impossible to operate the camera, even though the monitor output was fine. I assume this was down to the shutter running at 1/48, but the viewfinder refreshing at 60hz This was with Atomic 3000s, but without DMX control.


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#10 Mathew Collins

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Posted 11 February 2016 - 11:21 PM

I haven't had problems with Paparazzi strobes and the Alexa.

 

With the Atomic strobes, what I've found is that you get a cycle where it falls into sync with the rolling shutter and then it drifts out and you start getting partial frames.  So when I used them on a scene in "Extant", I basically had to call "action" when I saw the strobing sync with the shutter and we'd get a minute or so before it drifted off again.

 

Hi David,

 

Could you give some information about the requirement of 'sync with the rolling shutter' and 'partial frames'?


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#11 David Mullen ASC

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Posted 12 February 2016 - 12:07 AM

I don't know the setting on the strobe, but we tried to use whatever the longest duration was possible, and then when we fired the strobes and rolled the camera (the strobes were going off in regular intervals), we could see on the monitors when the flashes reached a peak brightness without partial frames and then we called action.


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#12 James R Blann

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Posted 12 February 2016 - 09:49 AM

Thanks for the advice, guys. DMX controlled Atomic 3000's on order!


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#13 Mathew Collins

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Posted 13 February 2016 - 08:25 AM

I don't know the setting on the strobe, but we tried to use whatever the longest duration was possible, and then when we fired the strobes and rolled the camera (the strobes were going off in regular intervals), we could see on the monitors when the flashes reached a peak brightness without partial frames and then we called action.

 

David,

 

Could you explain 'partial frames'?

Why 'rolling shutter' is an issue here?


Edited by Mathew Collins, 13 February 2016 - 08:27 AM.

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#14 David Mullen ASC

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Posted 13 February 2016 - 11:03 AM

http://www.diyphotog...olling-shutter/


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#15 timHealy

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Posted 13 February 2016 - 01:14 PM

I have always not minded the rolling shutter where you can see the strobes come in and out of sync at the end or Alien where Sigourny Weaver gets on the shuttle with the cat. But there's lots of stuff going on visually.


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