AV1 CRF default?

Ffmpeg AV1 is a fantastic codec. Open and promising a better compression ratio than HEVC / AVC.

However I am unclear right now about the possible CRF settings.

x264 defaults to a CRF of 23 x265 defaults to a CRF to 28

These two seem to have a similar visual quality for me.

What is the corresponding CRF for AV1 – what CRF has a similar quality and what is the default?

Please excuse if this question was asked before. I googled and searched reddit. However I only found complicated answers wits PSNR etc but no simply estimate answer.