Moire pattern (shirt) fix in Sony Vegas

Moire pattern on presenter’s shirt when footage’s image size shrunk from HD to much smaller.  Was a corporate shoot where lecturer wore a finely lined shirt (doh!).  Tried a few experiments but a googled solution worked best, as follows.  I applied a Gaussian blur as a MediaFX, so it (hopefully) got applied before the pan/crop downscaling.  Worked well in any case.

    • Your problem is moire. If you want to understand why you have this problem Google “Optical Low Pass Filter”. This is a vital part of any digital camera both still and video. When you downscale an image to a lower resolution the OLPF is no longer enough to filter out high frequency detail at the lower resolution and hence you hit problems with the Nyquist Limit.
    • You fix this by reducing the resolution BEFORE downscaling. This is easily done by using the Gaussian Blur FX in Vegas. You only usually need a tiny amount and can adjust the amount depending on what is in front of the camera. Values of 0.001 to 0.003 should be more than adequate. You may only need to apply it in the vertical direction. …you will need to experiment to get just enough image softening to stop the aliasing without making it too soft.
    • …you need to do this BEFORE downscaling. Render at Best quality mode. Do some quick tests

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