Vertical line flicker in animation

In meticulously reviewing your AfterEffects project, I acknowledge the intricacies of addressing flickering in vertical lines at the specified 25 frames per second. Your efforts in experimenting with techniques like reducing Interlaced Flicker, incorporating animated grain, and applying slight blurring showcase dedication to quality. To further enhance your animation, consider adjusting composition settings for optimal pixel aspect ratio alignment and exploring advanced anti-aliasing options. Additionally, precise keyframing and alignment on the pixel grid could prove beneficial. Should you seek additional insights, feel free to visit my website (https://www.cclcricket.in/mumbai-heroes) for a more comprehensive discussion on refining your animation project.

That flickering is called Judder, and it is caused by the stroboscopic interaction of the frame rate and the speed of movement. The solution is to use an expression that moves the layer (the lines) exactly a whole number of pixels per frame. You get the same thing when panning a camera. The ASC Cinematographer manual used to contain a Critical Panning Speed chart for various frame sizes, shutter angles, and focal lengths. Generally, if you are planning the full width of a frame at 24 to 30 frames per second, you need the move to take 8 seconds. A little faster, and the shot will judder. Here are some current guidelines:

Panning Speed Best Practices - RED Digital Cinema | Professional Cameras

Cinematography Tip: Capture Smooth Panning Shots at 24fps - PremiumBeat

Cell animators (cartoons) and 3D animators have to be aware of these limitations. They are caused by the frame rate/speed of movement/our retinal retention (how long it takes us to process an image) and the contrast in the shot. The same thing happens with rolling titles and horizontally moving shots. Thin lines are especially problematic. 

The start of the solution with thin lines is to use an expression to move the layer a whole number of pixels per frame so Antialiasing does not make the lines change shape. Combine that with a move that is a little too fast, and you will get judder.  

It's pretty easy to figure out what speed you need to minimize the judder and the aliasing problems with thin lines. If the comp is HD, it is 1920 pixels wide. 8 seconds at 30 fps is 240 frames. 1920 divided by 240 is 8 pixels per frame. This tells me that if you move the layer slower than 8 pixels per frame, you will not get any judder.  I usually drop a couple of pixels to be safe. Give this expression a try for a 30 fps comp:

fr = 6;
t = time/thisComp.frameDuration;
x = t * fr;
[value[0] - x, value[1]]

That should fix your critical panning speed issue unless your monitor refresh rate is odd.

Hi GregorA,

Sorry for this issue regarding flickering. Did you ever find a solution? Please let us know if our expert's advice helped you or if you still need help.

Thanks,

Kevin

Use uneven values for the line thicknesses. This is a typical issue when they are only one or two pixels wide and due to the chosen velocity one edge of the line is always excessively sharp. "Crooked" values liek 1,2 pixels or similar will enforce better antialaising and suppixel sampling. Also of course consider slightly tweaking the scroll velocity to begin with and using motion blur.

Mylenium