Kalimar 2X power automatic teleconverter (converted to extension tube)

This is something I bought which the seller advertised as new old stock - he had taken it fresh out of the box and carefully deglassed it. When I received it, it literally had everything except the glass and looked as if it had been made yesterday. The instructions with which it came list Pentax AF teleconverters also, but this is the PKA/KR manual focus model.

As a macro extension tube, this device offers pass-through for aperture control data in SMC-A and subsequent lenses and about an inch of stand off distance. Data for focal length are not passed, and my DA50/1.8 wide open reported its aperture as f/1.7. However, it also has the manual aperture coupling required to work non-crippled film-era K mounts and can transform any reasonable K mount lens and camera combination from any era into a close-focus rig (which is why I bought it) if not a macro.

As a bonus, it has the Ricoh Pin and will thus support the appropriate automatic functions on Ricoh film bodies thus fitted, for those still using them. I do not have any of these and could not test these functions. This is a high quality product, and although it is Third Party, the Ricoh Pin is the rounded variety which allows the device to slip smoothly on and off my K-5. In addition, because this is a PK-A device with a metallic mount, it shorts the contacts in the appropriate manner to allow stop-down green button metering with third party lenses having anodised bases.

Because of the stand-off distance, this device is just about useless as an extension tube with any lens below 28mm. I tried it with the DA21/3.2 and the front element is practically touching the subject when most distant focus is achieved. Beyond about 70mm the advantages are limited and the returns rapidly diminish. Testing with the prime lenses in my possession suggests that any advantage is lost at around 135mm, depending on the minimum focus distance of your lens.

Further extensive testing is required with regard to image quality, but it fulfils the purpose for which I bought it. Those buying the device intact as a teleconverter for use on DSLRs should bear the limitations of its data transmission functions in mind, i.e. neither focal length nor MTF nor distortion correction profiles are likely to make it through to the camera. For this, it may be worth holding out for the Pentax AF model.