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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

EPIC Hi-Speed shutter adjustment

Andrew clemson

Andrew clemson

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Anyone managed to master flicker on the EPIC at 100 or 300FPS?

Seems like whatever I try I cant get rid of that darned flicker!

Any help or tips would be much appreciated. Is it a case of doing manual calculations to get an exact shutter angle to eliminate the flicker?
 
The old fashion way is double the HZ range. Flicker was a serious issue with film cameras, becuase you did not really know ubil you processed and had your film on a chain.

So in short, this is how is goes. Say 210-240volt @ 50hz power. 50hz is 50 beats or pulses of electricity per second. You don't really have pulse issues with tungsten lamps because of the slow burn time on the globes, but kino, flouro, sodium vapours, etc are all fast pusle lighting, thats why they seem to have a high frequency flicker to them by eye.

For all lights other than TUNGSTEN you shoot at 25fps no flicker. double it, 50fps, no flicker.. 100fps, no flicker, 200 fps no flicker, 400 fps, no flicker... 800 fps, no flicker.

The US power is more problematic... it's 110 volts 60hz. So it goes like this. At 29.97 (close to 30fps) you shoot 60 fps, there should be no flicker, 120 fps, should be no flicker, 240 fps.. should be know flicker, but remember your shooting at 29.97 not 30 fps, so as your frames rates build you time slips out ever so slightly giving you the flicker again.

Here's the other pain in the US. when we shot there last. we were getting HZ fluctuations from 58 to 61hz... very annoying.

So the secret is this, if there is any light source other than a large tungsten lamp, turn them off. then you can shoot at what ever frame rate you like. :)
 
Getting into high speed shooting means learning all about flicker! Below is from the Phantom FAQ I wrote for our website. It refers to the Phantom cameras, but the issues are the same.


Lighting for High-Speed

Lighting issues are not specific for the Phantom cameras but for high frame rate photography in general. Even with the great sensitivity of modern cameras, be prepared to use a considerable amount of light. Beyond illumination, the largest issue in high-speed lighting is flicker. Tungsten lights actually have a flicker rate. When powered by alternating current (AC) electricity, the power cycles 50 or 60 times per second (depending on the country and its power system). During the down cycle the tungsten lamp filament can dim slightly, causing flicker. The amount of dimming is related to the type of bulb, wattage and physical size of filament. In general, we have found that lamps larger than 2000 watts use tungsten filaments so large that they do not have time to cool and dim before the power cycles back up. Therefore, we recommend using 2K or greater tungsten light fixtures when shooting above 120fps in 60hz countries and 5K or greater when shooting above 100fps in 50hz countries. Be aware that a unit such as a nine-light is NOT a large fixture but is actually an array of smaller lights and as such can flicker.

Some additional recommendations are to use DC power for tungsten lights, which eliminates flicker entirely. HMI and fluorescent lights are generally fine for speeds under 120fps as long as they use electronic ballasts. Magnetic ballasts should not be used. HMI lights can suffer from “arc wander,” whereby a plasmatic “hot spot” can move about within the bulb, causing an amorphous shifting movement in the light output. LED lights are subject to the electronic circuits driving them which can create a vast array of refresh rates, but generally we have found that LED fixtures designed for the production community will not flicker as long as they are not dimmed.

Finally, the shutter angle on the Phantom can affect flicker as well, as a greater shutter angle allows for a longer response time from the light. When shooting extremely high frame rates, it may no longer be necessary to retain a 180-degree shutter to capture the motion generally preferred for a filmic look. A 360-degree shutter allows both more light sensitivity and reduced flicker possibilities.
 
Electrical stabilization.

As a side note, not all areas of the world have very stable electricity.
Frank Sinatra Jr., who has toured all over the world, told me that the most unstable electricity he has ever encountered was Las Vegas.
Needless to say, he throws heavy duty line conditioners on all of his equipment.
 
Thanks for all the suggestions guys.

Think it must be something to do with our power as "the big light in the sky" here (which is rather bright) produces fantastic results!

Will try the 5K or greater rule. Having said that was shooting some tennis this week with 18Ks and still noticed some considerable flicker at 300FPS after grading.

Before it wasnt noticeable.
 
Andrew
When you work with HMIs try 3 of them each one on a defrent fase it works for me with unstable power line situation they will cancel each other and look like fleeker free
Best
 
Turn genlock on to internal for a start.
I have a special Ballast for my 4K Arri HMI that I use to light the studio. I run at 1000HZ and I have found 180 degrees and slight increments of a degree gets it out.

You really need to look closely at the histogram to see that the flicker has gone.

Normal HMI's will flicker without the high speed ballast, or what Esmaile suggests also can work. The other option is use a petrol generator and you can usually wind out the flicker in the invertor.
 
Esmaile Neissi said:
Andrew
When you work with HMIs try 3 of them each one on a defrent fase it works for me with unstable power line situation they will cancel each other and look like fleeker free
Best
Click to expand...

Thanks, will give that a go. Will all three need to be from the same point or can they be at different parts of the studio?
 
I get you. Will try it when I get some downtime. Last shot of the day on my last job was on an 18K only and was still noticing after light grading on 300fps stuff.
 
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