Thanks for replies.. those images are renders. I tried turning min. shading rate down and it made no difference at all, so I didn't bother trying a further reduction.

Perhaps it's no wonder they're giving this one away.
Now that's completely out of character... see what this is doing to me?

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)