Please note: our M42 adapter ring could not be suitable for Pentax Takumar Super Takumar Carl Zeiss M42 series（aperture pin does not fully depress, small tabs sticking out), as ours depresses the aperture pin all the way down

1. Make sure the flower/tulip lens hood is correctly positioned: the correct orientation is with the larger peaks at the top and bottom and the smaller peaks at the side
2. It is a normal issue that when you shoot at angle of view 18mm, the vignette will be appeared on the picture.as the flower/tulip lens hood is not designed for one special lens, then could not guarantee that all the lens will not have the vignette issue,as long as the flower lens hood size=your lens size, then could be used. this issue could be improved just by slightly retun the lens hood and there you go been getting eliminated.