Mac OSX 10.11.6 fixed a security bug that indirectly caused a lot of TIFFs to be rendered black as viewed in the Finder, including those processed out of Capture One. The TIFF itself is fine, but to avoid this black-in-Finder syndrome you’ll need to change a rather obscure setting. In Process Recipe under [Basic > Options > Tile Dimension] select 128 rather than “Not Tiled” (which is the default).
If you’re interested in the details you can read here. But for most users, just changing that obscure Tile Dimension setting and processing images that aren’t oddly black when viewed in the Finder is all the time they need to spend thinking about this.
We expect this will be a new default in the next release of Capture One.