Adam Wilt has uncovered an error in Final Cut Pro’s still image export to still image routine- it fails to properly render applied filters before exporting the frame you want. The filters were used to correct for the fact that it also fails to properly “round-down” YUV video that goes over 100 IRE when exporting still images. It clips the whites. Yea, it’s about as dumb as the fact that FCP has to “render” MP3 audio dropped in the timeline, yet fails to do it correctly and you get garbled audio. Isn’t the point of “rendering” to make it work in FCP?
Thankfully, Adam has a simple workaround, which you can find on his Blog post here.