OVERVIEW

In 2006 Bo-ming Tong started the Conurus Imaging Corporation and began converting Contax N auto focus lenses for use on Canon EF and EF-S dSLRs. Bo-ming is renowned for superb workmanship and demanding standards. The Contax 50mm F1.4 N is my fifth lens from Conurus and his product quality today is just as good today as it was in 2006. Conurus has expanded their product offering which now includes all nine Contax N auto focus lenses, as well as the Contax 645AF NAM-1 adapter. The firmware is continually refined and now includes micro-step focus adjustment functionality, enabling end users to adjust focus calibration. Additionally, Conurus expanded their support and offers a limited warranty for some auto focus motors.

I recently purchased a converted Contax 50mm N in new condition with all the accessories, documents and box. For me the out-of-the-box experience was like buying a brand new lens for a Canon dSLR. The Contax 50N looks new and works perfectly on the Canon 1Ds Mark III. In April 2005 Kyocera announced the end of the Contax brand and ceased operations sometime thereafter. Finding new condition equipment five years later is not easy. The price was slightly higher, but given the condition of the lens and the completeness of the kit, I have no regrets.

THE CONVERSION

Conurus’ conversion addresses both hardware and software. The lens mount mount is replaced with a custom machined Canon EF mount, custom firmware is loaded into the lens and the electrical contact assembly is replaced. The lens firmware is upgradable (via Conurus) which is good news if Canon decides to change their protocols in the future. Mount tolerances are carefully measured, and if needed the mounts are shimmed for proper performance at infinity. Bo-ming records all the data on his website and owners can look up their data by typing in the lens’ serial number - which is quite handy when trying to determine what version of firmware was installed (click here for the tracking page).

Part of the conversion process includes calibrating the lens’ auto focus system. Historically Bo-ming calibrated the lens by testing it on a Canon 1Ds. Today end users can calibrate their own lenses via a series of button pushes and aperture ring turns. The process is a bit abstract at first, but after running through the steps several times it gets easier, click here for the instructions. The values are permanently stored in the lens (or until changed again).

Initially the Contax 50mm N front focused on the Canon 1Ds Mark III. The previous owner had optimized the 50N for his Canon 50D. Following Conurus’ instructions I reset the lens and after about 20-30 minutes of testing, a +20 adjustment looked to be very accurate. As time goes on, if there are any signs of front or back focus, I will “tweak” the lens via Canon’s in-camera micro focus adjustment since that is quicker and easier. I tested this and 1Ds Mark III’s in-camera focus adjustment does work with the Contax 50mm N.

BUILD QUALITY

The Contax 50mm N is a good looking lens on the Canon 1Ds Mark III. The Contax 50mm N is about the same size as Canon’s infamous 50mm F1.2 L USM. The Contax’s barrel is metal and feels solid. Surprisingly the lens only weighs 11 ounces, the balance on the Canon 1Ds Mark III is terrific. Being such a light lens, it makes the Canon 1-Series body livable for a day long outing.

The Contax GB-76 lens hood clicks into place easily - just line up the arrows and a small turn and it locks into place. To reverse the hood for storage, the process is the same. The hood locks into place very smoothly. Some of the hoods for the other Contax N’s were not as graceful, so the easy fit was a nice change. The front lens cap is the standard Contax K-61 which snaps into place easily and stays put (unlike the new Zeiss ZE caps).

Mounting the lens is the same as mounting any Canon EF lens. The lens mounts smoothly and easily - there are no rough edges on the bayonet to foul the process. Once mounted the lens feels solid, securely connected and there is very little rotational play (no more nor no less than a typical Canon L lens).

The focus ring is a bit vague, a tad spongy with some lag or play in the system. It feels similar to a Canon manual focus ring. The ring moves smoothly, but it is not dampened like a Contax RTS or Leica R lens. Manual focus is workable, but there is not an oo-la-la experience.