Cosina Lens Production

I had an interesting discussion today with one of my lens suppliers, after I received and had to return the new 12mm f5.6 M mount lens. On receiving the lens, I noticed what appeared to be a large dust spot on the edge of the lens and a smaller one on the opposite side, but neither would not come off. On closer inspection, the spots were actually in the lens. On even closer inspection, it appeared to be a shards of glass broken off in the assembly process.

I contacted the dealer and he said to send it back and I subsequently got a return call about the lens. The spots weren't broken glass, but actually bits of metal from the mould used to make the particular element. Here's the interesting bit; Cosina makes lenses for many lens makers, Voigtlander (their own brand), Zeiss, Canon, Nikon and possibly others and each batch is made with differing levels of QC, based naturally on the cost of the lens, so things like this can get through.

Apparently, lens repairers have long known about this and often know when a lens has come from the Cosina factory because of these sorts of random issues. Zeiss lenses get very high levels of QC, which is reflected in the price, but others not so much scrutiny. The Voigtlander lenses are still of high quality, but sometimes these sorts of faults get through because the QC isn't as demanding. That's probably also why Leica lenses demand such a high price, as every aspect of manufacture undergoes rigorous scrutiny throughout; there are no Monday lenses.

I might also note that the first batch of 12mm lenses were subject to a recall, but no one knew what the reason was, other than it may have had something to do with the M9.

I still have faith in the Voigtlander lenses, but it's interesting to know this and be alert to such possible issues.

Cheers

Ray