The Dandelion chip requires the lens to be dismounted (ie - disengaging the chip) and then snapping a shot within 3 seconds of the lens being attached to the camera. Entering the programming mode on the Dandelion chip is awkward (programming instructions here). I definitely do not like the idea of the chip passing over the AF contacts while the camera is turned on. There is a risk of bridging a circuit if the chip is not installed in the correct position on the adapter. However, in use the Dandelion chip and Optix V5 chip perform equally well. And, I love being able to reprogram the chip at home versus sending it back to the seller for reprogramming.

ADJUSTING FOR BEST FIT

To ensure the best performance, adapters need to be snug against the lens. The picture to the left shows a slot than can be expanded to hold the lens tightly against the adapter (adapters usually have three such slots). Insert a small jewelers screwdriver into the slot, twist the screw driver slightly to expand the slot. Expand each slot an equal amount. The goal is even pressure at all points between the lens and the adapter.

If the slots continually collapse over time, try placing a small small piece of aluminum foil into the slot. The piece of foil should be repeatedly folder until it is .25 to .50mm thick. Over expand the slot slightly, insert the foil and then close the slot so the foil is held in place. With the tabs properly expanded, the adapter and lens should be snug with no fore or aft play or wiggle. These adjustments will not change the adapter’s performance, but it does keep the lens from spinning slightly which can be annoying. 

WHAT HAS WORKED

I have tried different adapters over the years on the Canon 1Ds, Canon 1Ds Mark II and Canon 1Ds Mark III; the following adapters worked well: 

1. •Cameraquest - these are rumored to be made by Kindai and relabeled by Cameraquest (unless Cameraquest changed their supplier). The Cameraquest price costs about the same as buying Kindai from Japan.  The adapters are nicely made and in 2005 time frame the best option when it came to infinity focus. At $175 per adapter these are quite expensive.
   

2. •HappyPageHK - the focus confirmation variety have worked with the Leica 50mm F2 Summicron (ROM) and Leica 90mm F2.8 Elmarit (current version - both CAM and ROM). Subsequently I have started using the new versions with the Optix V5 firmware with the Leica 50mm Summilux-R E60.
   

3. •Fotodiox - I did not have good results with Fotodiox adapters a couple years ago. They seemed too thick I think the adapter fell just shy of reaching infinity focus with the Leica 21-35mm ASPH, 21mm F4 Super-Angulon and 35-70mm F3.5 Elmarit. I recommend against the Fotodiox adapters.
   

4. •Zoerk (Zork) - Amazingly expensive and surprisingly poor build quality in my opinion. Perhaps my experience was unique, but considering how expensive the Zork adapter was, I was very disappointed.
   

5. •Leitax - In June 2009 Leitax started offering their Canon EOS / Leica-R adapters. Their adapters screw to the back of the existing Leica mount, thus eliminating wiggle & wobble. In theory this should be a very solid connection.
   

6. In May 2010 I ordered a Leitax kit for the Leica 50mm Summilux-R E60. The fit and finish of the adapter is excellent - the highest quality I have seen yet. The lens mounts easily on the 1Ds Mark III and is very solid. There is very little rotational movement (ie - where the Canon locking pin on the bayonet clicks into the adapter). I purchased the adapter with the Dandelion chip already installed and purchased the screw driver and plastic tool for removing the rubber ring from the 50mm Summilux’s rear element.
   

7. While I am not a fan of stop down metering, Leitax’s Leica-R / EOS adapter solution is the best I have used thus far. If someday Leitax offers similar quality solution for Contax / Canon adapters, most likely I would switch from the HappyPageHK Contax/EOS adapters to Leitax’s products. The above comments are not an endorsement or recommendation, just my first hand experience. I receive no financial support from Leitax, HappyPageHK or any of the adapter sellers. I am a paying customer just like you.
   

8. The PebblePlace.com Leitax Leica-R / Canon EOS adapter review is available here.
   

Based on my experience, the Leitax adapters are my preferred solution. I definitely prefer having the adapter SCREWED to the lens. Recently a Contax lens slipped past the locking tab, spun on the adapter and almost fell to the ground. Fortunately the 1Ds Mark III was on a tripod and I had a very firm grip on the lens at the time. It was a very close call. Since that experience, I have a much greater appreciation of Leitax’s solution.

My only niggle with Leitax is the Dandelion adapter. Programming the Optix V5 chip is easier. That said, once these chips are set, they are more or less a “set it and forget it” affair. I have not bothered to micro-adjust focus on either the Optix V5 or Dandelion chip. After reading the instructions, both seem like a pain. These days if I am in doubt about focus, Live View is my BFF!

One last comment about the Optix chip. There does not appear to be any distinguishing marks to tell what version an Optix chip is. I recently purchased a used Contax lens and the seller included a HappyPageHK Pro adapter. After alot of DOF button pushing, nothing happened, so I can only assume this was an earlier that could not updated by the end user. So, if buying a used adapter in the secondhand market, be sure to quiz the seller about the adapter, its version, etc.