# 5d Mk3 exposure pulsating



## basadembo (Nov 20, 2014)

Anybody know what might be causing the exposure to pulsate from normal to overexposed on my 5d mk3 videos?
Thought it might be an LED light I was using somehow causing frequency interference but that's not the case.

Thanks


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## ajfotofilmagem (Nov 21, 2014)

We can see a sample of what you describe?


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## basadembo (Nov 21, 2014)

Sure
How do I get a .MOV up on here?


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## Tonyphotos (Nov 21, 2014)

Do you mean when you're looking on the back of the LCD screen during live view AND when using AUTO focusing the exposure flicks under and over as it's trying to find focus? If that's the case it's totally normal.


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## basadembo (Nov 21, 2014)

No, it's there in the clip made more obvious once downloaded and viewed on a monitor.
It's a throbbing up and down of about a stop in exposure throughout.


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## Marsu42 (Nov 21, 2014)

basadembo said:


> How do I get a .MOV up on here?



Upload it to some free filehoster, then give the link. If the clip is too large, simply run it through handbrake and then upload the downsized version with lower bitrate as it's only about demonstrating the problem.


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## basadembo (Nov 21, 2014)

Thanks Marsu42

https://www.dropbox.com/s/4qmo2tz2jkmkgf4/Pulse_2.mp4?dl=0

The only thing that "clicks" when viewing it, is the red battery low symbol that flashes at about the same rate - but although that shouldn't be an issue and there are other similar clips where the batteries were not low.


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## basadembo (Nov 21, 2014)

here's a better version...

https://www.dropbox.com/s/0fnarqjad76iltb/Pulse3.mp4?dl=0


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## IWLP (Nov 21, 2014)

What was your shutter speed set at and what part of the world are you in?

Also, what was Auto Lighting Optimizer set to? I'd try turning it off if it wasn't.


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## Marsu42 (Nov 21, 2014)

basadembo said:


> here's a better version...



Strange, looks like the metering couldn't decide on what part of the image to settle. I'm not much of a video geek, so I'm sure someone will come up with settings that can make the camera stick to one exposure setting.


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## basadembo (Nov 21, 2014)

Manual, shutter speed 50th, UK, Auto Lighting Optimiser always Off, ISO not Auto,


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## tolusina (Nov 22, 2014)

basadembo said:


> .....
> Thought it might be an LED light I was using somehow causing frequency interference....


Was the scene lit with LED Lighting?
Best I know, there are (at least) two electrical methods for driving LEDs, current control and PWM (Pulse Width Modulation).
Current controlled lights will be steady.
PWM lights do indeed flicker rapidly, the frequency of the pulse as designed in determines the rate of the flicker, the width of the pulse (its duty cycle, ratio of on/off time per cycle) determines the apparent brightness of the light.

I have a rather bright LED flashlight (torch) with three brightness settings.
Low and medium both use PWM, high is continuous.
I just demo'd this for myself (I doubt the concept will video well, I'm not even going to try) by watching spinning bicycle wheel spokes lit by the LED flashlight.
PWM makes the moving spokes appear as many multiples of spokes, continuous light just shows them moving.

If the frequency of PWM pulses is low relative to multiples of the shutter speed, yes, you'll be recording the effects of the flicker similar to the effects encountered when shooting a video display screen.
If the frequency of the PWM pulses can be cranked up to several multiples of the camera's shutter speed, the flicker phenomenon will still be present but likely not apparent (or at least less apparent).


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## Mt Spokane Photography (Nov 22, 2014)

Usually, the aperture changing when you are right on the verge of one aperture or the other. DSLR video is best done in manual mode so that you do not get aperture changes causing what looks like flickering.


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## basadembo (Nov 22, 2014)

@ tolusina - an LED ring light was used and that was my first thought on seeing the results but there is also footage shot outside lit only by natural light where this is happening and although it might seem to be doing it in parts of the frame, it is in fact happening throughout the whole frame - just that it's more pronounced to the eye where it's darker.

@Mt Spokane - shot in Manual - only thing on Auto was WB

It's not 100% consistent on all clips - about 85% of them - which makes it unpredictable and to find the cause more important.


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## Viggo (Mar 1, 2015)

Tonyphotos said:


> Do you mean when you're looking on the back of the LCD screen during live view AND when using AUTO focusing the exposure flicks under and over as it's trying to find focus? If that's the case it's totally normal.



I have that issue and it's crazy annoying. I use the face AF for the kids, and often tap the AF-on button to refocus, any way to avoid that crazy exposure difference when focusing ?


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## wyldeguy (Mar 5, 2015)

I know this thread is old but the file in Dropbox is missing so I can't give my 2 cents worth on the problem. Any chance I could see the video so I might be able to diagnose? I do work with video all day and have seen my fair share of weird failures.


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## Viggo (Mar 5, 2015)

wyldeguy said:


> I know this thread is old but the file in Dropbox is missing so I can't give my 2 cents worth on the problem. Any chance I could see the video so I might be able to diagnose? I do work with video all day and have seen my fair share of weird failures.



It's very easy to replicate. Just tap the focus button under recording and you'll see.


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## wyldeguy (Mar 5, 2015)

Viggo said:


> wyldeguy said:
> 
> 
> > I know this thread is old but the file in Dropbox is missing so I can't give my 2 cents worth on the problem. Any chance I could see the video so I might be able to diagnose? I do work with video all day and have seen my fair share of weird failures.
> ...


Was that the determined fault? I didn't get that impression from reading the thread. To me it seemed like it wasn't fully agreed upon and there was no official "yup that was it"


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## YuengLinger (Mar 5, 2015)

I had a cousin who got arrested for pulsating exposures within 500 feet of a middle school.. :


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