I recently shot some pieces to camera against green screen shooting S-Log to 4k ProRes with the Odyssey 7Q, then keying with ultra key in PPro.
In the past, I've had hassle-free keys just using 1080 avchd. The ProRes was quite a bit trickier - mainly around the hair, but also in terms of there still sometimes being noise present despite the matte view showing full transparency.
Going back over my steps, and yes, the green screen probably could have been lit more evenly, but it was well within the tolerances of what Premiere's been able to work with previously and still give 'perfect' results.
If anyone has any workflow recommendations for chroma keying S-Log, it'd be great to hear them.
How did you shoot it? S-log's 18% grey is 38% and 90% white point is 65%.
It's different than Rec 709 zebras. Did you view LUT's in the Q?
if you're still stuck in LOG, you need to convert to linear either with a lut or profile.