Time stretch won’t stretch over 3 seconds, why?

[Steve Bentley]

There is a limit to the stretch effect – 9900 %
If you go into prefs you can have a frame fill the comp (its under import) or be any other set length.
You can also enable time remapping on the layer and you can then extend its out point to the end of the comp.

Am I missing something? Time stretching a frame wont make the motion last any longer because on one frame there is no motion.

[Ryan Elder]

Okay thanks. I never knew about time remapping and it seems to have worked! Thanks.

Basically I want to stretch one frame into several frames of that one frame. The frame is a wheel, and I want the wheel to spin, while superimposed on other footage. If that makes sense?

I also tried turning on motion blur to make the wheel spin more convincing looking. However, I can’t really tell a difference with motion blur turned on or off, unless maybe it has to spin fast in order to tell?

[Steve Bentley]

If you just want to see it in the comp, you have to turn motion blur on in two places – on the footage layer itself and up at the top of the timeline window there is a matching icon (two over from the shy icon and one to the left of the motion graph editor button). Turn that on as well and the blur will show up in your comp (assuming that the object is moving or rotating).
That top button is there so you can designate certain layers to be motion blurred in each layer but leave leave the overall effect off when you are working with your comp as it takes longer to process that effect. Think of it as a global motion blur button (but only for layers that have their own motion blur turned on.)
The default settings for rending tells AE to turn on that top button when rendering but it couldn’t hurt to check in your render settings that it is indeed set to on for rendering.
If you want to make the blur more or less, you can adjust the shutter angle in the comp settings window (cmdK or cntrlK) under the advanced tab. The default is 180 degrees which refers to how a motion picture camera used to work (their shutters were circles with a wedge cut out that light in – the wider the wedge/angle the longer the film was exposed and thus a longer blur). So a higher blur would be in the 270 degrees range – but more than that it starts looking unreal, unless that’s what you are after.

[Ryan Elder]

Okay thanks. I tried clicking on both icons but can still see no motion blur. Perhaps the wheel is not moving fast enough for there to be a lot of motion blur maybe, as it’s suppose to move slowly. I just want the regular 180 degree motion blur :).

However, when I click on the motion blur icons, the clip all of a sudden becomes a third shorter, and there is no way I can stretch it back out to it’s length without ruining other parts of the effect. For example, there are key frames that zoom in on the wheel and change the position of the wheel, and if the clip becomes shorter from adding motion blur, and I try to stretch it back out, then I loose the keyframes.

Is there anyway to fix this?

[Steve Bentley]

Can you post the project? I’ve not seen a layer shrink unless the originating footage changes. I don’t know how a motion blur would make a layer shrink.
Even with a slowly turning wheel you should see a little blur.
Something is up here.

[Ryan Elder]

Okay thanks. When you say post the project do you mean a test video of what I have done so far, or actually post what I tried doing in after effects?

[Ryan Elder]

Another thing is, is that I am working in Premiere Pro, and from Premiere Pro, I send the clip to after effects and then add the motion blur, but the wheel only turns in Premiere Pro. Could the motion blur get lost when it goes back to Premiere Pro from After Effects, since I am turning the wheel in Premiere Pro?

[Steve Bentley]

The key frames that turn the wheel need to be in the application that is adding the motion blur/ Its the animating that does the blur – once it is just a set of pixels you would need realsmart motion blur or some other package to pick the motion out of the footage to determine the blur – and that doesn’t always work as you might expect.
So if you did the animation in Premier and brought that footage into AE, all AE knows is that its just a movie. It has no motion data to work with.

[Ryan Elder]

Okay thanks, so you are pretty much saying that AE cannot read the motion of the wheel in Premiere and I would have to rotate the wheel in AE then?

[Steve Bentley]

Correct. AE measures the values between one keyframe and the next and then does the math to figure out how much motion blur to apply. No keyframes come from premiere (that I’m aware of – but I’m not a premiere guy). What comes out of premiere is just a movie. You might be able to export keyframe data in an edl but I doubt it. Do the animation in AE (where it should be done anyway for best control) and apply the motion blur there and then bring that rendered element back in to Premiere (with alpha if needed)

You could apply a smart motion blur effect like Real Smart Motion blur which can look at the pixels and figure out the blur from a movie that has no motion blur on it but the effect has its limitations (and it’s not cheap) – if something comes in from an edge the effect doesn’t know what to do with those new pixels because as far as it’s concerned they haven’t started moving yet, they just appeared. Overlapping objects at different speeds can also cause trouble. Its not perfect but it is impressive given what it’s got to accomplish. It’s literally tracking every pixel. A doff of the propeller beanie to the guys who invented that!