These $100+ lens adapters (not Metabones brand) that claim to offer an increase in F stop (speed boost) and prevent the cropping... are they effective and is there a loss of resolution when using them?

Found this one on Ebay that looks promising. Note the pics of corner detail.

https://www.ebay.com/itm/283384878178?ViewItem=&item=283384878178

Have a very sharp Minolta FD 35mm (still camera) lens that becomes a 52mm coverage-wise on my JVC camera. If I could retain the 35mm (using an optical adapter) I'd have two focal lengths in one.

Anyone had any luck?