October 4th 2018: I will be updating this page so check back soon.
To see how this lens performances against the some of the best objectives that I own see a detailed test at 4x here on Closeuphotography.com: https://www.closeuphotography.com/stacked-vs-objectives
After testing more than a dozen lens combinations this lens combination was by far the best, in fact the image quality was some of the best I had ever seen. This lens is very sharp and is consistent from edge to edge and the CA control is excellent. This lens combination is sharp from f/2 to f/4.5 but the performance peak seems to be about f/2.8.
The Schneider Makro-Symmar 120 has fantastic APO correction and is just a great lens overall by itself. The Xenon f2 lenses are not as popular as the later Componon lenses but I have found these to be much better performers than the 28mm and 35mm Componons.
Stacked vs Extension
Stacked or coupled lenses are a pair of lenses mounted face to face for macro photography. The performance from a pair of stacked lenses at 1x or higher can be much better than a normal macro lens focused using extension. A f/3.5 lens focused at 4x by extension only would have an effective aperture of f/17.5 but when you focus at 4x with that lens reverse mounted on a telephoto, the effective aperture would be f/14. That gain of 2/3rds of a stop can make a difference in image sharpness.
Mounting Adapters
This setup was made using items I had in hand but since I have seen the performance of this lens I have ordered a 40.5mm to 30.5mm male to male adapter. I will update this page with a report and information on where to buy one.
V38 V-mount Adapters
Out of all the V38 adapters I have tried the Schneider adapters are much better. The no-name V38 adapters have clearance problems with some lenses like the Makro-symmars and Macro-Varons I own although they might work with other V38 mount lenses like the APO-Componons and other brand lenses.
LINKS FOR MORE INFORMATION
The Makro-Symmar 120/5.9 Industrial 12K lens lineup on the Schneider Optics website (USA):
https://www.schneideroptics.com/Ecommerce/CatalogSubCategoryDisplay.aspx?CID=1353
The Makro-Symmar 5.9/120MM-0059 model used here on the Schneider Optics website (USA) website:
https://www.schneideroptics.com/Ecommerce/CatalogItemDetail.aspx?CID=1353&IID=6000
Schneider’s V38-line Scan Lens lineup including the 120/5.9 lens:
https://schneiderkreuznach.com/en/industrial-optics/lenses-v38-line-scan-macro-system
Makro-Symmar 5.9/120MM Data Sheet PDF:
https://schneiderkreuznach.com/application/files/8115/2845/3944/Makro-Symmar-5.9-120-0.75x.pdf
Makro-Symmar 5.9/120MM talk on Photomacrography.net:
https://www.photomacrography.net/forum/viewtopic.php?p=221728&sid=ce04e6ee77464c9e027cb52f2e04cb28
Makro-Symmar HM 120 5.9 lens
A detailed test report on the Makro-Symmar 120 lens in the B-0 mount called the 120 Makro-Symmar HM including comparison images is available here on Closeuphotography.com:
https://www.closeuphotography.com/schneider-makro-symmar-120mm/
Xenon f/2 lens discussion on Photomacrography.net:
This is an older discussion but there is still interesting with lots of info.
http://www.photomacrography.net/forum/viewtopic.php?t=7354&