Thank you! Yep, Pentacon Electric is a vintage manual lens. It has some "auto" switch which blocks aperture blades in the position of f/2.8-4, but it's not compatible with Nikons, so I use it as fully manual lens. Since it has M42 screw mount, to affix it on Nikon body I need an adapter. The adapter has additional lens, enabling it to focus to the infinity (that's just how Nikon works), unfortunately it does screw up quality of the photos (esp. below f/5.6) a bit. However, comparing Pentacon to other vintage lenses, it's the best choice - it's one of the sharpest, has multi-coating thus performs nicely even in full sunlight, no part of the lens retracts thus hitting camera's mirror or adapter (it's the issue that for example Helios and Carl Zeiss Jena lenses have).