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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 11 Dec 2010 (Saturday) 17:22
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Reverse-engineering Canon EF lens protocol

 
CheshireCat
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Dec 13, 2010 18:49 |  #31

woos wrote in post #11446033 (external link)
As long as he reverse engineered the protocol, you are 100% in the clear. You could even implement your own version of it in your own cameras (like sigma does, they use the EOS signalling!) This is fine.

OP, just say you are reverse-engineering Sigma's signaling, not EOS.
Then you are 200% in the clear, and I don't think Sigma is exactly in the position to complain :p


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x_tan
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Dec 13, 2010 19:38 as a reply to  @ post 11446409 |  #32

Just wonder who will be the 1st person here to butch a good L :lol:


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crmorse
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Dec 13, 2010 21:22 |  #33

What about posting to wikileaks? haha. sorry. couldn't resist. Seriously good hard work. If you do publish, I'll be reading.


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ken_vs_ryu
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Dec 14, 2010 07:15 as a reply to  @ post 11437106 |  #34

this is great. how much money for the electronic stuff?


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rvdw98
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Dec 14, 2010 09:16 |  #35

Fureinku wrote in post #11446305 (external link)
if i keep reading this or stare at that picture any longer, my head will literally explode. Out.

No it won't.


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woos
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Dec 15, 2010 14:06 |  #36

what would be really interesting is if you could somehow reverse engineer the way that canon adjusts AF calibration of the lenses. I've always wondered that. There must be a way to write calibration info to the lens' firmware.


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crmorse
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Dec 21, 2010 19:36 |  #37

I'm pretty sure the AF calibration is stored in the body. That's why you have to pick (on the higher end bodies) whither to store the calibration for all lenses of that type or only that specific SN. I think the logic goes roughly like this: AF like normal -> apply stored AF calibration -> fire.


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fnothaft
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Dec 21, 2010 22:58 as a reply to  @ crmorse's post |  #38

Subscribing as well, would be glad to help if any sort of FPGA based controller design was desired.


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charithjperera
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Feb 03, 2011 20:57 as a reply to  @ fnothaft's post |  #39

Wow nice bw!,
I got an older 28-70 2.8 sigma lens that gives communication errors on my 400D and I'm trying to make your third type of converter to filter the comms to make the camera think all's good but pass all the focus control signals. Aperture signals seem dud so i'm also looking into trying to get thoese signals corrected.




  
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Feb 03, 2011 21:35 |  #40
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The obvious project is to use a Canon lens with some non Canon stuff. Add it to a webcam or make some very high accuracy rangemeter.
Or slap that 70-200/2.8 II on Nikon camera.




  
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ivicyrusivi
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Feb 04, 2011 15:47 |  #41

so this could be used to mount a canon lens on a nikon body, and maintain full functionality?

Has anyone done this with nikon? would love to be able to mount a nikkor onto my canon body!


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phigment
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Feb 04, 2011 15:50 |  #42

ivicyrusivi wrote in post #11777787 (external link)
so this could be used to mount a canon lens on a nikon body, and maintain full functionality?

Has anyone done this with nikon? would love to be able to mount a nikkor onto my canon body!

Well, canon lenses have a shorter register distance, so you would lose infinity focus.

And you would also need to know the nikon communication protocol as well.


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krb
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Feb 04, 2011 15:53 |  #43

ivicyrusivi wrote in post #11777787 (external link)
so this could be used to mount a canon lens on a nikon body, and maintain full functionality?

There are physical issues that would prevent this unless you wanted every lens to be a macro lens.


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krb
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Feb 04, 2011 16:10 |  #44

AntonLargiader wrote in post #11443183 (external link)
What have you seen, communication-wise, about focusing and focus confirmation?

I'm curious about why lenses can be out of focus when the camera thinks they are in focus.

AntonLargiader wrote in post #11446409 (external link)
What about the whole 'get the lens calibrated to stop the front-focusing' thing? I don't understand it either, but it seems to be real.

based on what I've seen posted in other threads, the AF process works something along the lines of:

- AF sensor looks through the lens and identifies a subject to focus on
- AF system calculates distance to subject
- AF system tells lens "focus to x meters"
- lens sets focus to "x meters"

For everything to work correctly, the camera AF system needs to be able to accurately calculate the correct distance and the lens needs to be able to focus at the specific distance it is told. This requires accurate positioning of physical elements as well as calibration of electrical components in both the camera and lens.


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AntonLargiader
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Feb 04, 2011 16:18 |  #45

That's been my impression also, butI don't think it's just distance - I think it tells the lens, "Move this much in that direction" but that's just my hypothesis. Reading through some Canon AF materials it really does seem to calculate what the focus error is rather than the distance.

However, a subsequent tap should bring it closer to being correct. Misfocusing lenses seem to stabilize at the wrong spot. That's why I wondered what sort of communication had been deciphered. :)


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Reverse-engineering Canon EF lens protocol
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