I have just bought a fotodiox chipped adapter for M42 to EF canon mount.

I am hoping to be able to use the canon autofocus sytem to get focus confirmation.

I have mixed results after following the broken English instructions. So I was hoping there was someone out there who was successful with getting this to work.

I am following the instructions in the lower half of the page called

Programming the Dandelion Chip.

The instructions say to set the aperture to certain values the press the shutter release, as a means to program the chipped adapter.

Does this mean to depress the shutter release fully, as in take a picture? Or depress half way.

So for example to communicate to the chipped adapted that you lens is f3.5 maximum aperture, you would put aperture to F64 then press shutter release, the F57 and SR, then F64 and SR, then f3.5 and SR to set f3.5 , then press F57 then SR, F64 then SR, then F57 then sr.

Once I set the aperture and focal length of the lens, it was back focusing heavily.

To calibrate this it says to change the focus value. Default value is 27, and 1-12 , 28-31 are front focusing values, and 13-26 are back focusing values. What does this mean?? If my lens is severely back focusing, what is the value I want to choose? Do i choose back focusing values to correct back focusing, or do I chose front focusing values to fix back focusing?


2 Answers 2


I thought it was halfway, but after a little more digging, I think it is a full exposure.

Somebody wrote up some notes here that might be of some help.

I don't know the answer to the question about the focus adjustment, but based on the way that is worded, I suspect that they wrapped a 5-bit integer in a very strange place, such that:

13 - very back focused
14 .. 25 - getting closer and closer to the center
26 - slightly back focused
27 - default
28 - slightly front focused
29, 30, 31, 0?, 1, 2, ... 12 - progressively more front focused 

with 12 being the max in one direction and 13 being the max in the other direction.


Having this chip on the adapter will not "Auto focus" your lens, the idea of programming the chip is so that the EXIF data will reflect the lens used for taking the photo. The lens can be used in AE or Manual mode but focusing must be performed manually, the chip fools the system so that you can use the focus confirmation lights to confirm focus as you manually focus.

  • \$\begingroup\$ I think you misinterpreted the language in the post. It was never explicitly stated that the adaptor would somehow focus a manual lens. In addition, this answer does not answer the question in anyway. Did you mean to post a comment? \$\endgroup\$
    – Scorb
    Jan 31, 2018 at 16:50

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