I want to preface this who article by stating that the "light flicker" is not something that is wrong with the camera. It is something that naturally occurs with the usage of artificial/studio lighting powered by AC current. There is a great in-depth explanation about lighting flicker at high speeds at the Abel Cine website in a FAQ about the Phantom High Speed Camera.
I set out to test the flicker using some indoor tungsten studio lights. I shot the footage at 240p with a 1/500 shutter (In an effort to comply with the 180 degree shutter rule).
Viewing the footage shot, the flicker was not completely evident until it played back in slow motion on my computer. It was indeed there. The question now is ... can I fix it?
I have dealt with flicker in the past when doing outdoor time lapses. The flicker there was a result of my iris not being fully open, and the image was not consistently exposed with the same exact duration. This created a wide variety of uncontrolled variable light changes. The flicker in studio is a little different because it is caused by a controlled source. For these situations, I was able to minimize the flicker in post by using Adobe After Effects "Auto Levels" effect with somewhat large temporal spacing. Obviously the more permanent solution to my time lapse flicker problem was to operate with the iris fully open every time. I invested in ND filters that let me keep my camera wide open while still dragging the shutter. Now I don't need to worry about post processing the footage.
The flicker present for high speed video in artificial/AC lighting situations is quite different. I tried my "Auto Levels" technique with out much effectiveness. It minimized the presence of it just slightly but I was not satisfied with the results. My next step after researching the ways in which other users have tried to combat high speed flicker, was to try the "color stabilizer" effect available in After Effects. The effect has 3 options "brightness", "levels", and "curves". After fooling around with each of the options and combinations of the 3 options through layering, I still was not satisfied with the results. The next option for me was to utilize the plug-in GBDeflicker by Granite Bay Software Inc. The plug-in is quite popular in the time lapse community, so I thought I would try it out for my situation. I was again able to minimize the flicker, but again it was not to my liking. I was starting to think that I would only be successful in a completely controlled lighting environment (which, from my research, would mean LED lights) which at this time might be out of my league as far is investments in equipment goes.
My Solution
My solution came to me when I started to think about my work normalizing and leveling photographs in Photoshop. I would sometimes layer the same image and control levels within using some of the blending modes. Knowing that both Premiere and After Effects offer the same blending options, I set out to see if I could make something work. From here on out, I will detail what I did in Premeire (The same principles apply for After Effects).
1. I took a sequence with my video file on it and layered the same file on a separate track.
2. I then offset the top video file by 1 frame.
3. I changed the blending mode of the top video track to "darken".
Lo and behold to my astonishment, the flicker was gone! After all of these trials, a simple blending method was what had cured my high speed flicker.
Disclaimer: Now I have not yet tried this trick in different lighting situations (florescents, HMI etc.) and at different shutter speeds (360 shutter for example). But for a tungsten studio setup using the FS700 at 240p, I was able to almost completely (at least to my eye) remove the flicker.
I am interested in other people's experience and if this technique works for them as well. Let me know in the comments below.
