Need opposite of motion blur in AE

[T Milner]

This may be an odd request, but I have imported documents moving slowly across the screen, and would like to keep the type as sharp as possible while they're moving, so that people can track them with their eyes and read them if they want to.  They're sharp when playback is stopped, but they become slightly blurred while playing.  It's 1920x1080 at 59.97 fps.  Are there any settings which might help, or is this just not possible?

AE CC 2017 on an iMac.

Thanks,

T Milner

[Rick Gerard · Accepted solution]

FAQ: Why does horizontal motion stutter (judder) in my movies, such as during pans?

[T Milner]

Thanks for the reply, Rick, but judder isn't my problem.  At 59.94 fps, the movement is plenty smooth.  It's just that the type is slightly blurred while its moving, even though motion blur is off.  It's a 5-minute video showing printed materials, constantly moving (per client's request).  If this is an unavoidable phenomenon, I can tell them that.  I just want to make sure I'm not missing something which might correct it.

Thanks,

T Milner

[Rick Gerard]

First, you didn't read the articles. The motion has to be exactly an even number of pixels per frame. Otherwise the edges will alias. Speed has everything to do with that even at 59.97 FPS. Besides that, there's retinal retention and a bunch of other human factors that you have to design for.

Video operates on a grid of pixels and the human eye does not like to smoothly track areas of detail. Try panting smoothly around the room with your eyes. The motion of type on the screen, unless it is full screen, is really really hard to follow and everyone perceives it a little differently.

All higher frame rates give you is more choice in the speed of the movement. The movement still needs to be exactly on the pixel grid for every frame. It's really really difficult to even lay out type exactly on the pixel grid. There's your answer.

[T Milner]

My apologies.  I didn't realize the two problems were related.  I'll try calculating the pixel count, and see if that helps.

Thanks,

T Milner

[Rick Gerard]

The easiest way to do that is to set up an expression for movement based on the frame duration. That way it will work with any frame rate. Set your "hero" position using Anchor Point with the comp panel magnified to about 800% so you can clearly see the vertical edges of the type and get them positioned as well as you can, then add an expression to position. You may be tempted to use the auto scroll behavior preset but personally I think it is junk because it does not take into account the frame rate so you can get speeds that just don't work very easily.

I use something like this for position:

f = time/thisComp.frameDuration;

s = 2;

[value[0] + f * s, value[1]]

f gives you the frame number, s is the number of pixels to move per frame, the last line is simply the position array that reads the current position of X so you can adjust it to anything and then adds the frame number times the speed. As long as "s" is a whole number you'll get a repeatable alignment of the text on the pixel grid.

After that you have to preview at full screen and several viewing distances to find out if your eye can smoothly track the text. You'll probably find one viewing distance that works for you and others that don't. Don't go crazy with this. You can't make it work perfectly for every human on every screen size at every viewing distance. It's just the way we are built.

[T Milner]

Thanks, I'll give that a shot.

[Rick Gerard]

You may want to have the text move from right to left. The expression I gave you moves from left to right. Just change the + in the last line to a - to reverse the direction.

You also have to consider the effects of compression. If you are delivering an h.264 MP4 then your color is going to be sampled in blocks of 16 pixels so if your contrast  is high (black letters on a white background) then you'll have to keep the speed an even number of pixels to have any chance of avoiding compression artifacts on the edges of the fonts. 2, 4, or 8 pixels per frame vs 1, 3 or 5 for example. All this gets very complicated and it's usually a good idea to find a speed that works and stick with it. Less fussing around in the long run.

[T Milner]

Excellent.  I'll have to do some experimentation.  I appreciate your taking the time to help me out.

Thanks,

T Milner