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Preventing Flickering: Shooting 240fps at Event Location

slow motion 240fps flickering

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#1 Karl Stelter

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Posted 21 November 2013 - 10:47 PM

First time poster, but have absorbed much from these forums over the past few months!

 

I have a live event shoot coming up tomorrow that I'll be shooting 240fps on a FS700 for some nice slowmotion shots of people in a single, indoor area - however from tests I've done (with ambient + tungsten to replicate the venue) I've gotten some pretty terrible flickering.

 

Problems:

1. No control over ambient lighting in the area (indoors)

2. Small indoor area

3. Limited gear allowed in area (1-2 lights, flags would be pushing it)

 

Any ideas on what I could do to make this video the best it can be, or at worst, remove the flicker in (shudder) post?

 

Would really appreciate some help on this, really want to deliver a high quality video for this client!

 

-Karl


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#2 Brett Bailey

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Posted 22 November 2013 - 03:52 AM

Experiment with your shutter speed.  Perhaps, 1/250.


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#3 Stuart Allman

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Posted 22 November 2013 - 10:57 AM

Karl,

 

It's really going to depend on the size and type of lighting fixtures installed at the event venue.  Even with a 1k I was seeing flicker at 240fps when I tested the FS-700, but just as Brett says, slowing the shutter speed greatly helps.  I've also seen problems with LEDs.  Some "event" LED fixtures flicker really bad even at 30fps.

 

You might want to test at the actual venue to see what the installed fixtures do.  For any lights you add, you might want to consider a video purposed LED unit, like Mole, Nila, Litepanels, or a plasma light like Hive.  Perhaps you can mostly over-power the event light such that remaining flicker isn't objectionable to your client.

 

Then again, you might be able to fake it by shooting at 120fps and slowing down to half in post using AE or Twixtor.

 

I was faced with a similar problem for a shoot coming up next weekend.  We pre-tested each of the fixtures and chose to go with a mixture of LEDs and larger tungsten fixtures while shooting at 120fps.

 

Stuart

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#4 Guy Holt

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Posted 22 November 2013 - 11:11 AM

... I'll be shooting 240fps on a FS700 for some nice slowmotion shots of people in a single, indoor area - however from tests I've done (with ambient + tungsten to replicate the venue) I've gotten some pretty terrible flickering.... Any ideas on what I could do to make this video the best it can be....

 

Another option is to convert the power supplying the indoor practicals and your movie lights to DC.  Any tungsten lamp can operate DC as well as AC.

 

CPS_Cultivate_Studio_HS_Prod.jpg

 

In response to a DP’s recent posting on the CML, where he was looking for some way to power a chandelier flicker-free for a high-speed commercial shoot shoot (pictured below), I built him a 120V AC to 120V DC power converter so that he could power the chandelier and other practicals flicker free at high speeds. He shot with it several weeks ago and reported that it “performed beautifully” and at  “2,000fps was rock solid.” 

 

CPS_30A_Power_Converter_SM.jpg

 

The one I built for him could handle up to a 1000W tungsten load, but I have since scaled up the design to handle a Jr. with CXZ lamp. The larger converter (pictured here) will accept input AC voltages from 90-140V, and 190 – 250V and put out a constant 120V DC. It can operate at both 50 and 60 Hz. It also has a series LED display to indicate the total load put on it between multiple tungsten Fresnels and incandescent practicals.

 

And, as you can see in the picture above, it is a lot smaller and lighter and more easily concealed on a set than ten 12V deep cycle marine batteries, wired in series, which has been the traditional approach to powering tungsten lights with DC on stages.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental & Sales in Boston.


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#5 Karl Stelter

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Posted 25 November 2013 - 10:30 PM

Wanted to thank you all for your ideas - I ended up shooting with a 1k / 500w tungsten at 120fps, 125 shutter and was able to get some solid slowmotion w/o flicker. 240fps just wasn't possible in the environment at the last minute ;( The DC conversion idea is brilliant also!


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