Everyone wants to be a "hipster" these days, I'm still not sure what they are really, in my day they were trousers that hung from the hips, still anyway, I don't want to be left out.....so I bought a "hipster lens"
Pentacon 135mm F2.8....15 blader ..Zebra version......Bokeh monster....With a name like that it's got to be good! Only five elements and it looks like single lens coatings, it's absolutely built like a tank.
From Ebay at £57 listed as good condition with slight misting at the edges of the front element from a Polish seller.......it arrived this morning.....looked good and, with a metal lens-hood. The front and rear elements were cleaned in a quarter of an hour.....fine!
The project is to use the lens on all four of my camera bodies, the Pentax K01/K3.....and the Nikon D7100 but it's main use will be on the Nikon D750 FF, where it's bokeh will be at it's smoothest and it should be a little sharper as well.
The problem is... although the Pentax adapter gives infinity focus without any additional optics. In it's standard form the non optical M42-Nikon F adapter will not, the lens needs to be closer to the sensor.
The Pentax registration distance is 45.46
The Nikon registration distance is 46.5......so the Pentacon need to be 1.04 mm closer to the Nikon sensor to achieve IF. (please check this for me BC?)
However the M42-Nikon F chinese adapter has a flange thickness of 0.9mm so overall I will need to approach the D750 sensor by about 2mm.
The Pentacon's lens mount is a solid demountable affair that has plenty of thickness, 1mm can be turned off the flange collar that sits up against the rear of the lens and there is 4mm of thickness behind the M42 mounting thread, so I shouldn't have a problem finding the remaining distance. When mounting the Pentax adapter an appropriate spacer will have to be fitted.
There's the project, I'm still waiting for the adapters, the UK post is a joke, the lens arrived in three and a half days from Poland.
BTW. I was also worried about the rear of the lens hitting the mirror, but even at infinity focus the rear element is well recessed.
Check out the blades!