Correcting exposure flickering in time-lapse footage "in post"

9

3

I have made some time-lapse footage of a flower blooming. It was taken inside, at night, with constant lighting. The pictures are great, but as footage, the exposure between frames is slightly inconsistent (probably beacuse one of the lights was fluorescent), resulting in a "filmic" flickering effect. The effect is actually quite cool (in an early 20th century kind of way), but I want to see what it would look like corrected.

I had assumed that it would be pretty quick and easy to correct this sort of thing in After Effects. I've tried using Auto Contrast, Auto Levels, and Auto Color (with and without temporal smoothing enabled), but they don't seem to correct the flicker at all.

What I want is to equalize the total amount of "light energy" (sum of pixels values) per frame, using an exposure adjustment. Anyone know how I would go about doing this (in After Effects or other software)?

aaaidan

Posted 2012-02-25T20:27:09.597

Reputation: 98

Sorry, I don't know the answer, but how many days did you spend on this? And how often did you take a picture? :)Friend of Kim 2012-02-25T21:31:44.380

If I were you I'd do it again. This time you'd set the camera to Manual and be sure that the lightning in the room is the same on all the pictures. This is because equal lightning and equal settings equals to equal exposure. Sorry. :(Friend of Kim 2012-02-25T21:33:10.477

I actually told a white lie to simplify the question. It's actually several hundred pictures of a flower, taken a few seconds apart. I used a controlled stepper motor to rotate it a fraction of a degree between exposures. The exposure is only very slightly inconsistent, but because it gets played quickly it's quite obvious. I think it's inconsistent because the exposure time was so short (as short as we could get), but we needed a very tight depth of field. So I think we'd have the same problem if we re-shot (with the same camera at least).aaaidan 2012-02-26T21:57:30.283

(that's why I mentioned "stop motion", cos it wasn't really a time lapse, as such)aaaidan 2012-02-26T21:59:42.557

Well, wouldn't it work if you set your camera to f/2 and 1/250, ISO 100 and don't change the lightning?Friend of Kim 2012-02-26T22:25:41.843

It is not clear to me that the exposure controls (Iris and Shutter) were locked down for the entire recording. What about white balance was this locked down and to the appropriate light source? ...and what is the lighting, tungsten? fluorescent? If you were shooting with a fast enough shutter and using fluorescent the camera might pick up the slight flicker of the fluorescent lamps.filzilla 2012-02-27T20:46:27.710

Answers

5

GBDeflicker plugin for after effects does the trick

willard

Posted 2012-02-25T20:27:09.597

Reputation: 66

Awesome. Only $99 standalone. A free solution is ideal, but this is a pretty good answer.aaaidan 2012-07-06T02:59:16.703

6

The flickering you are talking about comes because you have chosen a too narrow aperture. Normally you can completely eliminate the flickering by choosing a wider aperture than f/8.

The reason is simple: The lenses are no longer controlled by a physical aperture ring. Today it's the camera's job to set the aperture, and if you choose a f-number higher than 8, the aperture has to move a lot in a short amount of time. This leads to an accuracy of maximum 96 %, thus resulting in 100-96=4, 4 in each direction: 4*2=8 %. This means that each picture can be up to 8 % different in exposure. (This percentage is of course dependent upon how good your camera and lenses are.)

But as you already have your footage shot you need to fix it on your computer. There aren't many programs to do this, in fact I couldn't find any, but a good one is Photoshop CSX Extended. The Extended version can work with video, thus making you able to correct each frame individually. But this leads to a lot of job!

Luckily for you there has been made an action for Photoshop CSX Extended to automate this process. (Think of it like a plugin for After Effects.) Just load your video and apply the action, and it will fix your footage completely!

The action is a part of a big action bundle called iNovaFX which only comes with this eBook: http://www.gmbooks.com/product/CS5.html. On this page you can see it in action!

I hope this will solve your flickering video! Have a good day!

Friend of Kim

Posted 2012-02-25T20:27:09.597

Reputation: 892

This leads to an accuracy of maximum 96 % I don't understand where you got the numbers. Do you have a source for that?Saaru Lindestøkke 2014-04-07T13:47:42.860

@BartArondson Unfortunately I don't have the source anymore. The source stated that most cameras have an accuracy of up to 96%. The more you pay for the camera, the more accurate it will (likely) be. The point of my answer being that all cameras have some deviation, and that deviation is causing flickering on higher f-numbers.Friend of Kim 2014-04-07T17:02:03.583

@FriendofKim Ok, I see. I understand you point that cameras are not accurate, but a big part of your answer bases itself on this "fact" so it's a pity that you don't have the source anymore.Saaru Lindestøkke 2014-04-07T23:36:56.607

Excellent answer, thanks! I didn't know that PS extended existed, let alone could work with video. Cheers! You will likely receive this bounty.aaaidan 2012-03-06T10:11:22.810

Thanks! The difference between the standard Photoshop and Photoshop Extended is that the Extended version can work with both video and 3D models in addition to what the Standard version can do. So if you are into 3D modeling you could actually texture them in PS as well as other dedicated programs.Friend of Kim 2012-03-06T14:54:35.403

3

You should try VirtualDUB with the MSU deflicker plug-in. It's totally free and work better than other software I've tried. You don't have to tweak any settings, it's working directly. It's available for Windows.

fabien

Posted 2012-02-25T20:27:09.597

Reputation: 31

Thanks, I'd love to check this out, but yeah, Windows. :(aaaidan 2013-08-31T03:18:55.823

1

The constant lighting you are referring to is not enough. Did you lock down the camera exposure? white balance? Focus? If any of these items are left in auto mode on your camera, your going to get some kind of uneven variance in light.

What kind of light are you using? Since you are want a shallow depth of field and are achieving this with a short exposure the light source may be of interest as well.

filzilla

Posted 2012-02-25T20:27:09.597

Reputation: 2 278

Nope, I had set the camera to manual mode, manual focus, incandescent white balance. I welcome this input, but my question was more about how to correct this issue "in post", as re-shooting is undesirable.aaaidan 2012-03-05T06:20:14.690

Ah! You may very well be right! I was using a halogen and a fluorescent, the latter of which would explain the flickering at that exposure I guess. In any case, my original question still stands: "how can exposure flicker be corrected after shooting?"aaaidan 2012-03-05T06:22:28.277