This seems like an interesting gadget to put on a Nikon SLR and convert the Laowa 12mm into a shift lens. ideal for architecture photographers.

The converter is designed exclusively for Sony FE lens mount and fits on cameras with a Nikon AI mount. It has a 1.4x magnification so the 12mm lens becomes an effective 17mm focal length and has a 1-stop aperture loss

With the 360g converter in place you get a +/- 10mm Shift

Combined cost of the 12mm and shift converter is about £1170.

You can find more info from the UK distributor here Laowa lenses

A tele-converter is a budget accessory that will increase your photography options. The most common one is a 2x converter that doubles the focal length of your lens. Your 50mm lens becomes 100mm, your 70-300mm zoom becomes 140-600mm.

Vivitar made a number of converters through the 70s and 80s.

Teleconverters are ideal for photography such as sports and wildlife.

Advantages:

• increased magnification
• light weight
• cheap

Disadvantages:

• light loss
• quality degraded

Several teleconverters converters for sale here