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HELP! Need to de-flicker footage!!

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Jenn Lindsay
HELP! Need to de-flicker footage!!
on May 27, 2017 at 6:56:39 am
Last Edited By Jenn Lindsay on May 27, 2017 at 7:00:40 am

Hi folks,

I used a Canon C100 Mk II to shoot a bunch of footage and interviews in rooms with halogen lights. I saw the flicker in the monitor and did some on-site googling, and turned my shutter speed to 1/120 and put on the "clear scan" and automatic filter reduction modes but the flicker wouldn't go away. I only had that chance to do the filming so I just went ahead a shot and figured I could fix it in post.

I'm in post. I've got a deadline and I can't figure this out. I tried Philip Bloom's method of duplicating the clip, placing it above the original clip, moving it one-frame off and setting opacity 50% but it didn't work. I bought Seed De-Flicker, installed it, and it doesn't work. It only blurs the footage a little.

The Seed De-Flicker tutorial says to set your timeline and footage framerates to the same setting. My footage is shot at a 23.98 frame rate. But I read in https://support.apple.com/kb/PH12648?locale=en_US&viewlocale=en_US that it automatically confirms your clips to the 29.97i frame rate.

I tried to start over on a timeline with a 23.98 frame rate but Seed De-Flicker and Bloom's method still don't work.

This never happened with my stupid little Canon camcorder or my starter DSLR Canon T5i. I feel so stupid for shooting with the C100 and not knowing how to get rid of this huge problem.

Anyway, I'm desperate to reduce my flicker. Please, can you help?

http://www.JennLindsay.com
iMac 27-inch, 3.5 GHz Intel Core i7. 4GB GPU.
FCPX


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Mark Smith
! Need to de-flicker footage!!
on May 27, 2017 at 10:06:18 am

Were you shooting in the US or some country outside the US?


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Jenn Lindsay
Re: ! Need to de-flicker footage!!
on May 27, 2017 at 10:09:36 am

Thank you for helping. I was shooting in Greece.

My next shoots are in Uganda and Rwanda.

Thank you!!!

http://www.JennLindsay.com
iMac 27-inch, 3.5 GHz Intel Core i7. 4GB GPU.
FCPX


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Mark Smith
Re: ! Need to de-flicker footage!!
on May 27, 2017 at 10:58:17 am

Ok here's the deal:

Where you went wrong- In Europe which includes Greece, the power line frequency is 50hz. In the US , Japan and some South american countries the power line frequency is 60Hz. YOur shutter speed of 1/120 would have worked in the US but NOT in a country with 50hz power line frequency. Fundamentally there is a relationship between power line frequency and shutter speed in video and film. The shutter speed must be a whole number multiple of the power line frequency. So in Greece the power line frequency is 50 so shutter speeds of 50 (50/50), 100 (100/50) 150. (150/50) would work . Your shutter speed was 120 which is not a whole number multiple of 50 but rather 2.4 *50 hence you have the flicker problem caused by phasing between the shutter frequency and the power line frequency.

If you want to shoot 23.98 in the other countries you are going to visit, set your shutter to either 1/50 or 1/100 and you should be good to go. This frame rate& shutter speed combo possible with the C100. Problem solved.

In Rawanda you may still get some subtle flicker because I find that power line frequency is often poorly regulated in some 3rd world countries, so 50 hz may actually be 49.8 hz or something close but not exactly 50. Florescent bulbs may also be a problem as they are often used way beyond their service life and develop flicker and pulsing in their old age.


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Jenn Lindsay
Re: ! Need to de-flicker footage!!
on May 27, 2017 at 4:37:28 pm

This is so helpful; thank you.

Out of curiosity, and professional necessity,
what are the ideal halogen light settings in the USA?

http://www.JennLindsay.com
iMac 27-inch, 3.5 GHz Intel Core i7. 4GB GPU.
FCPX


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Joe Marler
Re: Need to de-flicker footage!!
on May 27, 2017 at 11:09:09 am

[Jenn Lindsay] "C100 Mk II to shoot a bunch of footage and interviews in rooms with halogen lights. I saw the flicker in the monitor and did some on-site googling, and turned my shutter speed to 1/120 and put on the "clear scan"...I was shooting in Greece....My footage is shot at a 23.98 frame rate"

Greece's utility grid is 50Hz, so your shutter speed should have been 1/100. That will take care of many problems. However I think Clear Scan might override this and allow dialing the shutter speed smoothly up and down. Depending on how that was set it could help or hurt.

If the lighting was halogen they were probably 50Hz. Increasingly a problem is LED lighting which uses Pulse Width Modulated (PWM) dimming that can cause problems at various shutter speeds. For those Clear Scan might be appropriate, assuming you have time on set to shoot test footage and review it.

To fix the problem after it's happened is difficult. The only tool I've seen that fixes a wide range of flicker and banding problems is Digital Anarchy's Flicker Free. It's expensive but relative to the cost of re-shooting, it's cheap. It works well but is very compute-intensive and slow to run. https://www.digitalanarchy.com/Flicker/main.html


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Jenn Lindsay
Re: Need to de-flicker footage!!
on May 27, 2017 at 4:38:13 pm

OK, maybe I will have to invest in that because I can't go back and reshoot the footage. Dammit. I really hope it works.

http://www.JennLindsay.com
iMac 27-inch, 3.5 GHz Intel Core i7. 4GB GPU.
FCPX


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Mark Smith
Re: Need to de-flicker footage!!
on May 27, 2017 at 5:13:59 pm

Here is another tip to kill off flicker when you shoot. This is especially helpful in those third world places where power line frequency is poorly regulated and or power is being provided by generators.

Set up a shot with the lighting you are going to use. Put something white in the frame where it is lit. Call up the waveform monitor on the camera's LCD screen and observe the white something you put in the frame in the light. If you see the white area on the waveform 'breathing" which is to say the white level is moving up and down slightly with a regular frequency , then your shutter speed and power line frequency are out of sync. You can use clear scan function to shift the shutter speed in small increments either up or down until the breathing stops. At this point your shutter speed and power line frequency are in sync and you won't have flicker.

In the US where power line frequency is 60 hz your shutter speeds could be 1/30, 1/60, 1/120, etc.


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Jenn Lindsay
Re: Need to de-flicker footage!!
on May 28, 2017 at 8:51:47 am

Mark, thank you SO MUCH for taking the time to help me!

I will try the white object trick. Am I supposed to just leave clearscan and auto flicker reduction on all of the time? Also, clearscan has just an on/off setting, right?

Is there some sort of website where I can find out standard Hz in countries where I'm filming? On the docket after Uganda/Rwanda are Norway, Sri Lanka, the US and the U.K./Ireland.

If you have any thoughts on ideal frame rate I'm happy to hear them. It seems FCPX prefers 29.98 but I don't know how that interacts with shutter speed.

Do you agree that my only hope for de-flickering in post is the costly plug-in?

So many questions. I appreciate your patience.

Thank you again.
Jenn

http://www.JennLindsay.com
iMac 27-inch, 3.5 GHz Intel Core i7. 4GB GPU.
FCPX


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Jeff Kirkland
Re: Need to de-flicker footage!!
on May 28, 2017 at 10:38:22 am

The easiest way to find the power frequency in any country is google. Something like "Sri Lanka power Hz" should get the result you need. I think the U.S. is your only destination that's not 50hz.

I've not used a C100 but when you turn clearscan on, you should also be able to set the frequency. Clearscan on any camera essentially lets you set odd frame rates to minimise flicker so if say 1/50th isn't working you can dial in something like 1/51.2, etc.

----
Jeff Kirkland | Video Producer & Cinematographer
Hobart, Tasmania | Twitter: @jeffkirkland


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Mark Smith
Re: Need to de-flicker footage!!
on May 28, 2017 at 11:14:48 am

Here's how I would approach your situation.
If you are in a 50hz power frequency country
1) set your shutter speed to 1/50 and check your picture for flicker under the lighting conditiond you'll use. If you don't see flicker then you are good to go.

2) If you do see flicker,Some times the AC power frequency can be a tiny bit off 50.00hz which will cause some phasing (Flicker) issues. This is a bit of a gray area which you may or may not be able to get perfect so be forewarned. Clearscan can help here but its really hit or miss. THis is where the white chip test can be of help though it can be hard to discern especially if the power line frequency and the shutter speed are very close - for example if the power line frequency is 49.9 Hz and the shutter speed is 1/50 the phasing or rise and fall of the white card on the wfm will be subtle and you'd have to watch carefully for maybe 30 seconds to see if it was happening.

HERE IS WHERE WE GET OFF INTO THE WEEDS, SO PROCEED WITH CAUTION. Unless you really know what you are looking for I'd default to a 1/50 shutter in 50hz countries and live with a tiny bit of flicker.
If the 1/50 shutter speed has very subtle flicker you can choose to accept it as it is very subtle or try to dial it out with clear scan. TO dial it out with clearscan first you turn on clear scan then use the function button to activate the shutter speed. Start with a shutter speed of 1/50 and then you can go up or down in fractions of a hz with the jog button. So you might go from 1/50 to 1/50.2 for example and check to see if the flicker is more or less pronounced, the goal being to find the shutter speed with the least flicker. I would not stray more than 1 Hz up or down from 1/50 because its unlikely the power frequency is THAT far off. So the range I would try would be shutter speeds between 1/49 and 1/51. All this said, tuning shutter speed with clear scan may not be perfect either, you may get lucky and find a setting that is perfect or just find settings that are closer to perfect but just a teensy bit off. Again I disclaim- we are off in the minutiae zone here.

3) I have a C300MK2 which apparently does not have "auto flicker reduction" so I can't weigh in on that . The C100 manual was not particularly informative about this function so I'll defer to anyone else here.

4) See this page for info about AC power in each country.
https://en.m.wikipedia.org/wiki/Mains_electricity_by_country

5) Shooting 1/120 shutter in Greece must have produced some major flicker . If you stick 1/50 in your 50hz countries you should be in good shape or so close that it really won't matter that much.


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Mark Smith
Re: Need to de-flicker footage!!
on May 28, 2017 at 1:44:00 pm

A bit of a follow up here-

I tried a couple of experiments to produce/reduce flicker by throwing off shutter speed from power line frequency with my C300 and failed miserably. It could be that there is some internal trickery going on within the 300 that the 100 does not have so some of my into the weeds details may or may not be accurate. I don't have a 100 to test with.

The safe route for you is to set your shutter speed to 1/ the power line frequency, be that 50hz or 60hz and go with that. Refer to the wikipedia link about power line frequencies in countries you may visit.

I hope this helps.


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Jenn Lindsay
Re: Need to de-flicker footage!!
on May 28, 2017 at 4:34:35 pm
Last Edited By Jenn Lindsay on May 28, 2017 at 4:50:40 pm

It is very helpful indeed.

I wonder how I can come to better understand the difference between system frequencies, frame rates and bit rates and how they interact with shutter speed. I get that the shutter speed and Hz of electrical lights need to be in multiples of each other, but I'm getting really confused about what 29.97i or 23.98, or 30p refer to (these are the three frame rates [?] in my timeline because I was shooting with the iphone occasionally (30p), and because a friend there recommended that since I was shooting AVCHD at 59.94 that 23.98 was better, so I changed from 29.97 about mid-shoot....)

But obviously I have no idea what all this means.

http://www.JennLindsay.com
iMac 27-inch, 3.5 GHz Intel Core i7. 4GB GPU.
FCPX


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Mark Smith
Re: Need to de-flicker footage!!
on May 29, 2017 at 11:32:37 am

Welcome to the confusing world of NTSC video "standards" otherwise known as 29.97i, 30P and 23.98.

Look here for some history about NTSC and frame rates.https://en.m.wikipedia.org/wiki/NTSC

Keep in mind that the same frame rate principles apply, but the number of scan lines in HD is of course 1080 not 525...

Practically what this means for your edit is that you have some mixed frame rates in your project which FCPX will handle . The best hing for you to do from here on out is to decide the frame rate for your project and stick with it. If you get an app such as Filmic Pro on your phone, you can then specify a frame rate like 23.98 or 29.97 that is in sync with your project structure and no have your iphone doing its own thing frame rate wise.

Having some historical perspective on the technical issues of video is of some interest such as how the implementation of the color standard which shifted the frame rate from a nominal 30 fps to 29.97 fps wayyyy back when still carries over to frame rates of the present day and we in NTSC land still do not have a whole integer frame rate standard liek PAL does with 25fps.

Whatever frame rate you are shooting make certain your shutter speed is 1/some integer multiple of the power line frequency- 1/50, 1/100 etc or 1/60, 1/120 . In the US 1/48 also works but I'm not going to explaing that before a second cup of tea and breakfast.

As a matter of personal taste I would opt not to shoot interlaced video, (the i in 29.97i,) because of the artifacts it produces can look like shit. Good luck with your project. If you are a tea drinker, I highly recommend going to the public market in Kampala and scooping up a pound or two of tea to bring back with you . The Tea there is awesome, You can also buy some fantastic coffee there as well so take your pick.


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Jenn Lindsay
Re: Need to de-flicker footage!!
on May 29, 2017 at 1:37:30 pm

Mark and Jeff and Joe, thanks to you guys this terrible mistake has turned out to be quite educational. I can't thank you enough.

I get that shutter speed / frame rate / halogen light Hz should all be roughly in a common multiple. This makes choosing frame rate easy-ish for my upcoming Rwanda/Uganda/Sri Lanka project, where I'll film in 24p and set shutter speed to 1/50, 1/100 etc....

However, what about my other project (both of them are described here: https://forums.creativecow.net/readpost/325/3209)? It is shot both within and outside of the USA. (I had no flicker issue in the USA or Norway with the T5i and iPhone; it all came in with the C100 in Greece). If I've done half of the filming so far in 29.97 and then shot in 23.98 in Greece, do you think I should go back to 29.97?

THANK YOU, and yes, I've heard about this amazing tea you speak of.... ☺
Jenn

http://www.JennLindsay.com
iMac 27-inch, 3.5 GHz Intel Core i7. 4GB GPU.
FCPX


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Jenn Lindsay
Re: Need to de-flicker footage!!
on May 30, 2017 at 10:03:05 am

Hey Mark,

Quick question.

If the iPhone is filming at 30fps but the lights in Greece are 50Hz, how come there's no flicker with the iPhone camera? It only happened with the C100.

Just curious ☺
Jenn

http://www.JennLindsay.com
iMac 27-inch, 3.5 GHz Intel Core i7. 4GB GPU.
FCPX, Motion
MacBook Pro 15-inch, late 2016, OSX 10.12.5
* Canon C100 Mk II
* Canon T5i
* Canon Vixia HFG20
* iPhone 6S+


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Mark Smith
Re: Need to de-flicker footage!!
on May 30, 2017 at 11:44:19 am

I would guess that the phone uses shutter speed to auto correct for exposure and probably flicker too. This is just a guess. If you look in your FCPX browser metadata at an iPhone clip you should see shutter speed in the inspector, and that might tell you something. If you were using filmic pro and had control over all the exposure and shutter speed parameters and set you phone to the same shutter specs as your C100 you might see flicker


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Jenn Lindsay
Re: Need to de-flicker footage!!
on Jun 8, 2017 at 9:15:16 pm

Hello Mark, et. al!

I want to thank you again for all of your help. I have been shooting flicker-free here in Africa!

I've been very busy filming probably way too much stuff and learning a ton really fast. At first I had a bad flicker at shutter speeds in multiples of 60s, just like in Greece, but thanks to you I learned my lesson this time and got it to 1/100ish and I was good to go.

I am also working with new equipment, a Zhiyun Smooth II smartphone gimbal which has been really fun, and an Atom 60 from Smart Slider. I've definitely underutilized these new toys as I've been really go go go and I don't have enough hands to handle everything. I hope I can get something cool out of the slider during my interviews tomorrow.

I've had some drama with a jealous monk trying to sabotage our filming but I think we're gonna be able to turn it into a plot twist. As far as I know, there's no Creative Cow forum to deal with corrupt Buddhist monks sabotaging production. ☺

Thank you again!
Jenn

http://www.JennLindsay.com
iMac 27-inch, 3.5 GHz Intel Core i7. 4GB GPU.
FCPX, Motion
MacBook Pro 15-inch, late 2016, OSX 10.12.5
* Canon C100 Mk II
* Canon T5i
* Canon Vixia HFG20
* iPhone 6S+


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Mark Smith
Re: Need to de-flicker footage!!
on Jun 12, 2017 at 12:21:57 am

Now that you have the technical gremlins out of your hair, have fun shooting !


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Joe Marler
Re: Need to de-flicker footage!!
on May 30, 2017 at 11:48:16 am

[Jenn Lindsay] "If the iPhone is filming at 30fps but the lights in Greece are 50Hz, how come there's no flicker with the iPhone camera? It only happened with the C100. "

Jenn, that is a good question. The problem is interaction between shutter speed (not frame rate) and power line frequency. Admittedly maintaining the 180 degree shutter rule will require a certain shutter speed which in turn is determined by frame rate: http://www.red.com/learn/red-101/shutter-angle-tutorial

We don't know what shutter speed the iPhone uses at 30 fps. Unlike stills, EXIF data is not as standardized for video so it's often difficult or impossible to analyze the file and determine video shutter speed. Oftentimes lower-end automatic video cameras will use a variable shutter speed to try and maintain exposure.

However a more likely reason you don't see this on an iPhone or small-sensor camcorders is they use a "global shutter", whereas large-sensor camcorders like the C100 use a "rolling shutter". Note these are both electronic not mechanical. A global shutter exposes the entire sensor at once, whereas a rolling shutter sequentially scans the sensor. A rolling shutter is an unavoidable technological limitation on many camcorders with large CMOS sensors, although a few do have global shutters.

For material shot by large-sensor rolling shutter cameras in regions with differing power line frequencies, there is no easy answer. It's probably best to use the locale-specific frame rate and 2x shutter speed, then in post figure out the best way to conform the footage. Normally you want everything shot at the same frame rate but in this case you don't have a choice. Conforming different frame rates is a lot easier than fixing a flicker or banding problem.


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Joe Marler
Re: Need to de-flicker footage!!
on May 29, 2017 at 12:21:54 pm

[Jenn Lindsay] "how I can come to better understand the difference between system frequencies, frame rates and bit rates and how they interact with shutter speed....but I'm getting really confused about what 29.97i or 23.98, or 30p refer to (these are the three frame rates [?]...I was shooting with the iphone occasionally (30p), and because a friend there recommended that since I was shooting AVCHD at 59.94 that 23.98 was better, so I changed from 29.97 about mid-shoot....)"

As first approximation you only need to remember a few things:

(1) Set shutter speed to 2x the frame rate. E.g, for 29.97 (or 30 fps) use 1/60th. For 25 fps use 1/50th sec.
(2) Normally the frame rate for your region will be a multiple of that region's power line frequency. E.g, countries with 50Hz AC power usually have 25 fps video. Countries with 60Hz AC power usually have 29.97 fps video. Provided you do this and adhere to rule #1, it solves many problems.
(3) Do not change frame rates part way through a production. It is more difficult to match the "motion look" and cadence when cutting between those.

There is no direct interaction between data bit rates and frame rate. However some cameras only provide certain bit rates for a given codec, which may also constrain frame rates. There is usually a table in the back of each camera manual which lists the codec, bit rates and frame rates for each shooting mode.

The frame rate nomenclature is confusing since many cameras abbreviate 29.97 as 30 and 59.94 as 60 to save display space. The iPhone shoots true 30 fps not 29.97 but it's easy to conform those since they are so close.


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