HELP! Need to de-flicker footage!!

[Mark Smith]

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.

[Jenn Lindsay]

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

[Mark Smith]

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.

[Joe Marler]

[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.

[Jenn Lindsay]

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

[Jenn Lindsay]

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+

[Mark Smith]

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

[Joe Marler]

[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: https://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.

[Jenn Lindsay]

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+

[Mark Smith]

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