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Image “leaking” through letterbox
I have an issue that keeps happening that I can’t figure out and that’s driving me nuts:
I commonly take 4×3 SD elements and do “fake” letterboxing; meaning I create black horizontal strips on a still image that’s 720×486 and put that as a top layer over my other layers. This gives me certain latitudes in shooting things and in re-positioning things in post.
Here’s my issue: The black bars seem to completely mask correctly for the most part, but I always get a scene or two that shows through on the bottom; I couldn’t tell you how much, but several lines’ worth and definitely visible.
This issue never shows in the preview window; only on renders. I did a snapshot on both problem scenes on my current project and they both were masked as they should be. I’ve even tried cropping the problem scenes within the intended letterbox area but that didn’t solve anything. I’ve checked and tested the pixel aspect settings for each bit of footage, too.
I realize this area peaking through may be out of safe action area, but (A) with today’s monitors I suspect everything SD will get shown on HD monitors and (B) it’s just distracting and looks unprofessional with footage “leaking”, and I don’t want to get questions from clients.
Any ideas what’s going on?
Thank you,
–Kelly
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5 Replies
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I think you have a “match aspect” issue going on here. The clip that is “leaking” has a slightly different aspect ratio than the letterboxed image on top. Do a match aspect on the leaking image first and see if the problem goes away. If not, then you need to do a match aspect on the letterboxed image and that should solve the problem.
Erik
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Erik,
Thanks, I’ll try that, but where do I find that to select it?
–Kelly
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Kelly,
There are many ways to do this so I will just give you one. Click on the event/pan crop icon on the event on the timeline. This will open the pan/crop window. Right click on the video image in the pan/crop window and select “Match Output Aspect”. This will conform the video to match exactly to your project settings.
Erik
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Hey Erik–
The “Match Aspect” didn’t do anything, but what fixed it was to un-check “Stretch to fill frame” on the pan crop window (which I still don’t understand, because nothing shifted after I did that, and I’m positive the “letterbox mask” image is the right size.
Oh well, you pointed me to a new troubleshooting tool anyway, so thanks.
–Kelly
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Your letterbox mask might not be the right size. See this topic for more info: https://forums.creativecow.net/thread/24/933275
That’s 873×480 for 16:9 widescreen. Using the same calculation method, 4:3 NTSC would require 655×480 pixels for still images with square pixels.
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