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Activity Forums Adobe After Effects Channel Blur Issue

  • Channel Blur Issue

    Posted by John Cuevas on March 28, 2011 at 7:06 pm

    Have an old background that I’m converting to HD and to eliminate some banding I added “Channel Blur”, bluring the blue channel 24 pixels. Well for a few frames the lower corner of the video completely loses it’s blue channel, leaving me with a bkg with a green square. After a few frames it goes back to normal. Happens a few times during the video

    Background RGB:

    Background Blue Channel Only:

    Just for giggles, I tried blurring the other channels and get the same problem.

    Johnny Cuevas, Editor

    John Cuevas replied 15 years, 4 months ago 3 Members · 4 Replies
  • 4 Replies
  • Tudor “ted” jelescu

    March 28, 2011 at 7:31 pm

    It is probably a compression issue. If your original clip is a mpg/h264/DV or any other compressed format you need to convert that to an uncompressed codec/sequence of files and then apply any fx.

    Tudor “Ted” Jelescu
    Senior VFX Artist

  • John Cuevas

    March 28, 2011 at 7:40 pm

    No video though, just 7 solids, some animating masks, a null, and an adjustment layer with channel blur.

    For fun I rendered out my BKG without channel blur, brought it back into AE, applied channel blur and it worked fine.

    Obviously, I can work around the issue. I’m more curious as to what is causing the issue.

    Uploaded the project, if anyone wants to take a whack at figuring this out:

    1808_bkgissue.aep.zip

    Johnny Cuevas, Editor

  • Brian Charles

    March 28, 2011 at 9:02 pm

    At first I thought the issue was the render order and could be solved by pre-comping all layers except the adjustment layer. No joy.

    So I added CC Composite to the top of the effects stack on the adjustment layer and it solved the issue but there is a slight color shift.

  • John Cuevas

    March 29, 2011 at 2:02 pm

    Thanks Brian. I’ll give that a try.

    I’m really kind of stumped with this, not a big deal, easy to work around it, but still puzzling.

    Johnny Cuevas, Editor

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