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Lens Blur Creating Blurred Bands?

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Seth ParkerLens Blur Creating Blurred Bands?
by on Oct 3, 2011 at 9:05:07 pm

I'm getting a strange problem with the Lens Blur effect in AECS5 (OSX Snow Leopard). My project is 16bpc. I have a video layer with Color Finesse, Lens Blur, and time remapping applied to it. Underneath and hidden I have a monochromatic precomp of solids I'm using for my Depth map. The Focal Distance is keyframed to go from its max distance to 0 over the course of 1 sec (29.97 fps). At around frame 20, I start getting blurred bands across my image that appear and disappear every other frame until the keyframing ends (Blurred Bands).

I've tried replacing my video with a prerender of the color and remapping effects and it did nothing. I've tried just readding the Lens Blur effect and it only changed when the bands started appearing by about 2 frames. Disabling Color Finesse does not make the banding go away. Copying the Lens Blur effect to an entirely different video clip does remove the issue (though I'm not sure I scrubbed through to see whether or not the banding just moved in time on the new clip).

So it seems to be, specifically, this combination of footage (file independent, as I've tried prerendering), depth matte, and lens blur effect.

I have some other clips with a similar effect being used, so I'm waiting for them to render to see whether they have the same issue. Things I've thought to try once I can use AE again: 1) switch to 8bpc 2) my final keyframe on the Focal Distance is using Easy Ease. Switch that to linear interpolation.

If neither of these things work, does anyone have any suggestions? Has anyone else experienced this issue?

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ben g ungurenRe: Lens Blur Creating Blurred Bands?
by on Oct 4, 2011 at 12:01:31 am

looks pretty buggy to me. Have you tried adding a little noise to your lens-blur reference image (the z-depth stuff)?

Ben Unguren
Motion Graphics & Editing

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Walter SoykaRe: Lens Blur Creating Blurred Bands?
by on Oct 4, 2011 at 12:16:24 pm

Have you verified that the depth layer is clean?

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
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Seth ParkerRe: Lens Blur Creating Blurred Bands?
by on Oct 4, 2011 at 1:55:44 pm

First, I tried re-keyframing my animation so that it started at a focal distance of 30000 and ended at 15000. Visually, this achieved the same effect (not really sure why 15000 is foreground in focus, though. Maybe I'm not doing this right?). However, this did not fix the issue.

Walter, I'm not sure what you mean by verifying that my depth layer is "clean." It's a precomp and the only thing in it is grayscale solids with masks applied to them.

I did find a couple of solutions, but each one has its concession.

Switching to 8bpc did make the bars disappear, but of course then I'm working in 8bpc. Probably not a huge deal with this clip, but not ideal if this happens for footage that it does matter with.

Adding noise to the z-depth layer also worked, but with a very minor, half-consequence. For reference, I added Noise to an adjustment layer inside my precomp. A setting as low as 0.5 worked. However, unchecking Use Color Noise created a weird speckling back in my main comp. Strange, but a moot point, as leaving it checked works. Also, slightly increased render time, per frame.

Finally, switching the interpolation back to linear also worked. The obvious concession here is that the timing of my animation is now slightly different. For my clip, not a big deal, but it could be in the future.

Thanks for your guys' help!

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