The Konica Hexanon Teleconverter AR 2x is a pretty rare piece of equipment introduced in the early 1980s for the Konica AR SLR system. The heydays of teleconverters were the early 1970s when cheap three lens [3L] converters from 3rd party manufacturers were sold widely (and inxpensively of course). Towards the mid-1970s Canon and Minolta had introduced some high performance converters specially designed for their FD 2.8/300mm Fluorite (Canon) and MD 5.6/400mm Fluorite (Minolta) lenses. Nikon would be following soon.

Around 1980 those specialized "long range" converters (300mm upwards) were supplemented by new "short range" converters for lenses in the 50mm to 200mm range. That was the moment when Konica introduced their first and only AR teleconverter, too. During this time Konica had lots of problems with unreliable electronic SLR bodies, and they were not the well respected company any more they had been in the 1965-1975 time frame. In addition around 1983 the 4/80-200mm telezooms really became popular, and thus the teleconverters (often combined with the ubiquituous 2.8/135mm lenses) became redundant. That explains the rarity of the Konica converter.

The Konica AR 2x converter is a pretty sophisticated [6/5] construction, and one would expect an appropriate performance. I have compared the Konica AR 2x converter & AR 1.7/50mm lens with the Minolta MD 2x-S converter & MD 2/50mm lens.

The results are pretty surprising and may explain why the Konica 2x converter wasn't selling well.

OK, here's the center wide open (effective f4 for both combinations since they support only f2 apertures), at f8 (eff) and at f16 (eff). The difference is clearly visible when the lenses are wide open. Stopped down to f4.0 (effective f8.0) the Minolta is tack sharp, the Konica not so much but still perfectly useable. At f8 (eff f16) both lenses suffer from diffraction.

But holy moly ... the corners ...!!!

Well, these are the corners. Minolta vs Konica, both with their best normal lenses on their original 2x converter.

I don't know what's going on here, but the results of the Konica converter are devastating. I don't think there's a problem with my specific sample of the Konica AR 2x converter, since it looks "like new" and was given to me together with its equally perfect lens quiver. BTW it's not just the corners that look bad on the Konica, but large parts of the image! Maybe the AR converter was designed specifically fro one of the Konica tele lenses (I'll check it tomorrow wih the 135mm and 200mm lenses), but it's certainly not usable in combination with the AR 1.7/50mm normal lens.

The Minolta 2x-S converter however really shines in combination with the MD-III 2/50mm lens. Slightly low contrast and some CAs wide open, but very good at f4.0 (eff f8.0), even in the corners, and nearly free from CAs. Well done Minolta!

2x Converter and 4/200mm lenses compared to Canon FD 2.8/400mm L and FD 4.5/400mm

Using 4/200mm tele lenses in combination with a 2x tele converter was nearly impossible on analog SLRs. The dark viewfinder, the finicky focusing and the film speed neccessary for handheld shots all were contributing to that.

On mirrorless FF cameras with EVF, in-body stabilization, excellent high ISO performance and easy lateral CA correction some of these limits can be overcome.

The combination of the Minolta MD-I 4/200mm with the Minolta MD 2x-S converter is pretty useable, especially at f5.6 (effective f11). Wide open the combo has a lower contrast and quite strong purple fringing. CAs are pretty strong - but not more than other conventional 400mm lenses such as Canon FD 4.5/400mm or Konica AR 4.5/400mm. Details resolution is OK, but not overwhelming; here the Canon FD 4.5/400mm certainly is better.

The Konica combination of AR 4/200mm plus AR Teleconverter 2x is quite a bit weaker, again. More CAs and fringing, and much less resolution, though not as bad as with the 50mm. Not really useable on 24 MP FF, tough.

I am still surprised about the low performance of the Konica AR teleconverter, and if anyone has a sample it would be interesting to dublicate my tests.