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Chroma Key Help, please?
Hey all,
I am working on a :30 television spot and am working with a Blue Screen. We shot on Beta SX and were able to pull a really clean key in Keylight. However, when looking at the final images on my broadcast monitor versus my Cinema Display I am seeing some (for lack of a better word) stairsteps going on within the image. Now, I don’t look at this as artifacting since it is not really happening around the edges of my actor. This anomaly is happening around where my actors hat (he is a 6′ 6″ Elf) meets his forhead.
When I look at the matte in Keylight, I am getting solid results. I could blur the layer before keying but that blurs the actors face more than I would like. Is there an image smoother or color smoother effect that I am missing/not using or don’t know about? Any help would be greatly appreciated.
Here’s how I captured – Captured via FCP from Sony Deck with Blackmagic 10 Bit NTSC codec. Exported sequence from FCP using Automatic Duck into AE. Interpreted Footage as Lower Field and checked the Preserve Edges box.
Thanks in advance,
SethOpportunity is missed by most people because it is dressed in overalls and looks like work.
Thomas A. Edison -
3 Replies
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How are you getting the image on your broadcast mointor ? Through a decklink box, or through a firewire DV deck ?
DV will downsample your chroma information.Are you sure you’re not just watching a deinterlaced output of your video ?
Do you see it on the final realtime output, or when freezeframing ?
Do you see it in the rendered quicktime ?It’s probably just an issue with the realtime preview you’re using.
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If your problem is what I think it is….a horizontal TEARING that appears in one spot of the shot during AE ram previews…its not a REAL problem, just a workflow annoyance. This tearing appears on the INTERLACED NTSC monitor attached to your Blackmagic card, but NOT on your computer’s screen in AE.
This may sound strange, but you need to (mentally) treat/consider the AE RAM PREVIEW output on the Decklink as if it is being processed/created PROGRESSIVE—-because it is—-its only interlaced on render output. (This affects your ANALOG monitoring.)
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Suggestion: Don’t, worry about these artifacts in your AE preview, RENDER a final file and output it from your NLE. Your final file will be interlaced…and I am guessing that THEN it will look fine on an NTSC monitor. -
You both were exactly right! I was previewing out of my Decklink card and was noticing some interlace/stairstep issues. Once I finally composited everything with a motion graphic background and other stuff, I rendered it out, threw it in FCP and…VOILA! Everything looks normal and there are no worries. Thanks for putting my concerns to rest. I greatly appreciate your time with this.
Seth
Opportunity is missed by most people because it is dressed in overalls and looks like work.
Thomas A. Edison
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