So I was able to pick up this 300mm lens for less than €5 euro and figured I should give it a try. My expectations of this lens were very low, and after testing it I still don't know what to think of it. It's not terrible, but also far from good. What are your thoughts on this cheap old telelens?

This M42 lens is made by Sankor and also known as: Admiral, Accura Diamatic, Optomax, Mayfair Sankor, Super Carenar.

Video is shot on a fullframe Sony A7 III in 4k 3840 x 2160
(I already sold the lens because I prefer my Super Takumar 200mm for tele-lens purposes)