Century x1.33 DS-WS13-58 arrived this morning ... proper testing to follow. Nothing scientific here! Just uploaded some flaring (pretty much the main reason I bought this adapter).
Footage was horizontally corrected by +33% in Premier Pro.
So for now, footage here is a 7D (1080/24P) with the WS13 screwed directly onto a Canon EF 85mm f/1.8 and also a Zeiss ZE 35mm f/2. Thankfully, no vignette on either of these. Will test wider ASAP.
The footage showing more pronounced, round flare elements is from the 85mm. The Zeiss 35mm tends to dampen almost all but the horizontal anamorphic flare.
It is possible to rack focus through this adapter; so quick & sloppy shots (suffering from excessive edge of frame softness & CA) can be pulled off by just focusing the prime OR if you bother to focus both the prime & the adapter, then the image quality improves by a significant amount.