Nokton48
Veteran
Yes that was the same experience I had with the 35mm F2 Canon. It vignettes on film (If you use an M8 the image is probably OK because of the crop factor). That is why I buy the original Canon Slimline filters. They made them for a reason.
I remember something else about this lens:
when a filter is mounted (I had a regular UV Hoya 48mm), the only way to put the hood on is to clamp it on the filter.
But then, IIRC, the hood vignets.
You may want to check this carefully before shooting somthing important.