Many T2 mounts and Vivitar lens converters have a numbering system to identify the camera lens mount fitting. This originated from Taisei Kōgaku the originator of the Tamron lens system. Vivitar also used the numbering system for their converters, so if you see one with 2x-4 you know it’s a 2x converter with a Canon FD lens mount.

Below is a comprehensive list of the numbering system for the T2 mount and the 2x and 3x converters of Vivitar. Other lens manufacturers may have adopted the same system. The ones in bold are confirmed as existing, others are discovered from researching various web sites, but I’ve never seen an actual example for sale.

TA-1 / 2x-1 / 3x-1: For M42 screw mount camera bodies such as Chinon, Cosina, Praktica, Zenit, early Asahi Pentax, Yashica  and Fujica

TA-2 / 2x-2 / 3x-2: For  Exakta camera bodies, and some Topcon and Praktica models with same mount. 

TA-3 / 2x-3 / 3x-3: For Nikon F/AI cameras bodies.

TA-4 / 2x-4 / 3x-4: For Canon FL/FD camera bodies.

TA-5 / 2x-5 / 3x-5: For Minolta SR /MC/MD camera bodies.

TA-6 / 2x-6 / 3x-6: For Miranda (M42 screw-mount) camera bodies.

TA-7 / 2x-7 / 3x-7: For Konica AR camera bodies. 

TA-8 / 2x-8 / 3x-8: For Konica F camera bodies.  

TA-9 / 2x-9 / 3x-9: For Miranda Sensorex Series cameras

TA-10 / 2x-10 / 3x-10: For Leicaflex

TA-11 / 2x-11 / 3x-11: For M39 (LTM/Leica) screwmount camera bodies such as Leica, FED, Zenit, etc 

TA-12 / 2x-12 / 3x-12: For Olympus Pen F / FT

TA-13 / 2x-13 / 3x-13: For Alpa Reflex camera bodies.

TA-14 / 2x-14 / 3x-14: For 16mm C mount 

TA-15 / 2x-15 / 3x-15: For Topcon / Exacta camera bodies

TA-16  / 2x-16 / 3x-16:  For Zeiss Contarex camera bodies.

TA-17 / 2x-17 / 3x-17: For Topcon Auto 100 camera bodies.

TA-18 / 2x-18 / 3x-18: For Zeiss Icarex camera bodies.

TA-19 / 2x-19 / 3x-19: For Kodak Retina Reflex

TA-20 / 2x-20 / 3x-20: For Olympus  FTL

TA-21 / 2x-21 / 3x-21: For Olympus OM camera bodies.

TA-22 / 2x-22 / 3x-22: For Pentax K bodies and Chinon, Ricoh etc with same mount etc

TA-23 / 2x-23 / 3x-23: For Fujica AX camera bodies.

TA-24 / 2x-24 / 3x-24: For Contax and Yashica camera bodies with C/Y bayonet mount.

BPM bellows with its interchangeable mount system is all well and good, but what if you cant find the right mount for your camera body? BPM haven’t made mounts for well over two decades, so the modern camera mounts are impossible to find. And some of the older mounts, such as Yashica/Contax, Rollei 35SL and Olympus Pen, are as rare as rocking horse poo.

You could possibly find a factory with a moulding facility to create some, but that would be costly, or you could gain access to a 3D printer and make a mount, but in both cases you would need an accurate 3d technical drawing to ensure the mounts fit correctly. Thankfully there is a solution and it’s not too expensive.

Some lenses sold between the 70 and 90s had an interchangeable mount. This system known as the T2 system, which also attached to the rear of some accessories, such as slide duplicators, had a T2 mount that screws on to the rear side of the lens or accessory and provides the necessary fitting for your camera body. The thread of a T2 mount is similar to that of an M42 camera thread found on Zenit, early Pentax and Praktica bodies, but is just slightly different. A T2 mount will screw onto an M42 thread but it wont go all the way so you just get a few turns – enough to make it a secure fit and the reason for this tip.

If you buy a BPM Pentax / Edixa screw thread mount with a male thread you can screw this into a T2 mount to attach to the bellows so your camera body can be attached. T2 mounts were made in a wide range of fittings and due to the fact many of the original 80s accessories have been reproduced by Chinese manufacturers, they have made mounts for newer camera bodies. So it’s very likely the fitting you want is available, and easily accessible from suppliers on eBay if your local dealer doesn’t stock them. We even have a few here at PhotographyAttic if you follow this link: T2 Mounts for sale