M49-M37 lens filter thread adapter for macro

My setup:

• Schneider Kreuznach Componon 28mm f2.8 reverse mounted on the hood thread (M37x0.75)
• Tube lens: Carl Zeiss Jena 3.5/135mm (M49x0.75)

It covers a full frame with noticeable vignetting at full aperture on the tube lens. 

Printed with PLA, 0.6mm nozzle, 0.1mm layer height. The thread came out very nicely.

I painted it black. 

https://www.closeuphotography.com/schneider-kreuznach-28mm-f2-8-componon-lens

Source: https://github.com/keshuaixu/microscopy/blob/master/m49m37.scad 

Requires fork of threadlib: https://github.com/keshuaixu/threadlib/tree/lens_threads