Flicker. It's a term that inspired the name of a social network for photographers (Flickr), but it is also an issue which can cause a video to have a slight brightness variation while playing.

It can concern real-time footage, but it's more frequent on image sequences that are used to create a time-lapse or a stop motion video.

When flickering occurs (stop motion and time-lapse)

The animation technique called stop motion consists of taking single pictures of a small set inside which plasticine characters are portrayed, with the crew moving them between each photo in order to simulate motion.

Given that many reflex and mirrorless cameras are not perfect concerning exposure, there might be very slight variations in brightness between one picture and the next. Individually, they do not bother, but when combining the sequences to create a video, the flicker becomes annoying.

For similar reasons, flicker also affects time-lapses. These kinds of videos are created by taking photos at fixed intervals which are usually from one to ten seconds. The images are then edited using software like Adobe After Effects which, finally, exports a speeded up video.

For the same reason flicker can occur with stop motion, unfortunately, it also happens with time-lapses.

Talking, instead, of real-time videos, a very frequent case of flicker occurs when fluorescent lights are used because they do not emit continuous light but turn on and off thousands of times per second, causing different exposures on individual frames.

In the latter case, you can successfully fix the problem in the shooting phase, using 25 frames per second (fps) if you are shooting in Europe, or 29.97 fps if you are shooting in the USA.

How to reduce flicker

Flicker depends on the lens and the camera you are using.

Many years ago, I changed my reflex camera, going from:

while I kept the same lenses.

Reflex cameras on tripods while shooting a time-lapse in a city at night

In that moment, the flicker, which I had never experienced before, appeared in my sequences. I tried all the old school remedies everyone talks about:

  • using a longer shutter speed
  • slightly unscrewing the lens
  • widely opening the diaphragm

No results at all.

Even with the cameras that I used later:

I found no solution to the problem.

Working in post-production was the only solution, using plug-ins that work with common editing software such as Adobe Premiere, Adobe After Effects or Final Cut.

In particular, I got satisfying results with GB deflicker.

My podcast

Some years ago, I started a podcast where I teach to photography and video shooting enthusiasts and professionals how to earn money with their job and passion.

Some of the questions they asked me concerned flicker. Here's what I answered:

A paid anti-flickering plug-in

Are there any free anti-flickering plug-ins for After Effects?

There are a lot of anti-flickering plug-ins for After Effects, but the ones I know are not free, such as GB deflicker, which I use and which gets its job done in an excellent way with no issues.

There are some After Effects functions that, even if they are not intended for de-flickering, you can use to contain the effect, but I have tested them and they are not that effective.

The only free solution I know is AVIsynth (download it for free from this site), which is an open source software that has two contraindications:

  1. 1. It is hard to learn because the interface is based on scripts, so it’s very different from traditional software.
  2. 2. It does not work with .mov, only with .avi.

Video editor while post-producing photos on his laptop

Flicker due to the Hz of lights

In some recent shots, I found myself with some sort of flicker in the video clips I created. I first couldn't understand if it was due to the use of my gimbal or the lens stabilizer I was using, or something else.

Then I found an interesting link:

Avoid Video Flicker: Understanding PAL (50Hz) & NTSC (60Hz)


where they talk about the flicker problem. In other words, there is an optimal shutter speed for video shot in PAL at 25 fps. Is it correct or did I misunderstand that it is 1/50?

If so, does it mean that all the other shutter speeds I choose could get me into trouble when it comes to video shooting?

You might have the flicker problem due to an incorrect shutter speed, but only if you are using artificial lights, and you can solve it (if you work at 25 fps) by using a shutter speed of:

  • 1/25
  • 1/50
  • any shutter speed divisible by 25 (1/75, 1/100, etc.)

It’s a problem caused by the frequency with which lights are powered.

If you want to avoid that kind of problem, you have to work at 1/50 of a second (or at 1/75, 1/100, etc.) or, in NTSC countries, like the United States, at 1/60 of a second (or at 1/30, 1/90 etc.).

In time-lapses, flicker cannot occur because of the setting of an incorrect shutter speed. If you use that technique you need to work with a shutter speed longer than half a second to get the right visual effect (as I explain on my course).

Flicker is a common issue in time-lapse sequences, but for others reasons.

Daniele Carrer

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