conurus

[Goldenspark]

Hi Conurus, I am a Canon user and stumbled across your site.
I wondered if during your reverse engineering of the EF lens operation you have uncovered the protocols for AF adjustment in the EF lenses? (That is, storing of a permanent AF offset)
I understand that your product doesn't talk to an EF lens, only emulates it looking into the Canon body, so maybe you haven't had to look that far?
I am really looking to do the reverse of what you have done and effectively set the AF offset myself.
Do you know how to do this, or of anyone who does?

It really does bug me that what I know to be a very simple operation is withheld by Canon.

Any help gratefully received!

[conurus]

We first shipped AF adjustment in a Contax Carl Zeiss Vario-Sonnar 24-85 lens on January 6, 2007 to a German customer and that was quite a bit ahead of Canon's announcement of the first camera body with AF adjustment, 1D mark III on February 22, 2007.

There are both variations among camera bodies and among lenses and we found that with f/1.4 lenses, the particular camera body would have to be matched with the particular lens to achieve optimal AF accuracy.

Both camera AF adjustment and lens AF adjustment have their place, as you probably have already concluded. If you use multiple camera bodies and multiple backup copies of the same lens, the only way to match every combination is to be able to adjust both the camera and the lens.

A few months ago a customer and myself evaluated 3 copies of the Planar 50/1.4. While their optical performance is very similar their optimal AF adjustment differ slightly. Using in-camera AF adjustment would not be able to tune to all 3 because to the camera body they are indifferentiable from each other and the camera body always applies the same adjustment to them. In-lens AF adjustment would solve the problem.

If you use our lens AF adjustment feature, the adjustment value is stored in non-volatile memory of our protocol conversion chip. Since there have been reports of AF drifting by different amounts at different focusing distances or at different zoom positions, our lens AF adjustment feature allows the user to configure different adjustment values for different zoom positions and different focusing distances. Unfortunately the adjustment procedure is quite complicated. However, if you do require this level of flexibility, it is there, ready for you to use.

We do not know if Canon lenses are equipped with similar non-volatile memory to store AF adjustment values. It may or may not exist and it may vary from lens to lens.

[Goldenspark]

Thanks for your reply.
I must say I am getting frustrated that Canon seem to be so secretive! I suppose it's not surprising.
I think I have found out that the lens AF offset that is stored in EEPROM in the lens is actually a number that is simply transferred to the body. It isn't something that the lens itself does anything with.
What I want to know is how in-body AF offset and lens AF offset interact.
I would love to get hold of the Canon lens calibratin software to have a play with the various lens parameters.
Thanks again for your time.

[conurus]

Our understanding is that the camera AF adjustment and the lens AF adjustment are simply added together.

[Tripple26]

This started with a Contax C/Y 21mm Distagon with an AF-confirm adapter on the camera. I tested every type of lens I have on it, Conurus-converted AF, Canon AF, and nothing revived it. It stayed non-functioning over night, then came back to life the next morning with a Canon EF 50mm f/1.4 attached. I swapped the Contax N (Conurus-converted) 100mm f/2.8 Makro-Sonnar on it, and it died immediately, and couldn't be revived.



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