What does this lever do in the EOS mount?

Poisson Du Jour said:

Lens mount index confirmation. The flange engages here and pulls it up, thus confirming with the body that the is in the correct position and electronic control state is readied.
It's best not to fiddle with it.

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Well, I have fiddled with it, in the sense that the adapter's bayonet now no longer engages the switch. That's made everything seem to work fine, contrary to when the adapter did push up the lever (mirror went up, shutter did not fire, mirror did not go down).

I wonder what the penalty for not engaging the switch is.

Poisson du Jour, can you elaborate on what you describe as the readying of the electronic control state?

flatulent1 said:

I'm going to ask the local camera tech when they open on Tuesday.

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That'd be cool. I'm very curious.

Me too.....I have had no bad effects or camera damage (yet?)

flatulent1 said:

I'm going to ask the local camera tech when they open on Tuesday.

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While you're there, ask if that flux capacitor ever needs any maintenance.

sandermarijn said:

Well, I have fiddled with it, in the sense that the adapter's bayonet now no longer engages the switch. That's made everything seem to work fine, contrary to when the adapter did push up the lever (mirror went up, shutter did not fire, mirror did not go down).

I wonder what the penalty for not engaging the switch is.

Poisson du Jour, can you elaborate on what you describe as the readying of the electronic control state?

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EOS bodies are electronic; legacy mechanical linkages, such as this one on the body flange, are about the limit of non-electronic interfaces. You will notice that if you remove the lens and try and fire, nothing happens: the body has safeguards to prevent firing without a lens attached. The lens mount transmits a huge amount of information to the body the moment it is mounted (positive click). It does so only when the index is positively engaged. If it is not, an error state is generated. IIRC through the MIR EOS site, the flange lever plays an important role in diagnostics when, for instance, the EOS 1N is connected to a technical interface via the hot shoe to assess control circuits, lens-body-body-lens communication, focus position, Tv/Av settings, shutter/shutter curtain delay and accuracy, drive readiness, drive wind and rewind cue (build up of tension at frame #36); there are many other checks possible. I imagine that if the switch is not engaged the body will not know a lens is positively attached and lens-body circuits are connected and ready.

The EOS 600 does not have a system reset (like the 1N, 1V) to clear fault states. I would not attempt to organise the camera yourself at the risk of incurring damage — it's not clear why the mirror is behaving in the manner you described.

More information (on all EOS bodies) can be found on the MIR EOS site (I am a contributor to this very large resource project): http://www.mir.com.my/rb/photography/hardwares/classics/eos/EOS-1n/htmls/MapEOS1n.htm)

Poisson Du Jour said:

You will notice that if you remove the lens and try and fire, nothing happens: the body has safeguards to prevent firing without a lens attached.

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Both my EOS 600 and 1N fire without lens, in all modes (PASM).

Poisson Du Jour said:

The lens mount transmits a huge amount of information to the body the moment it is mounted (positive click). It does so only when the index is positively engaged.

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With "index" are you referring to the AF switch (or what it should be called)?

Poisson Du Jour said:

If it is not, an error state is generated.

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Not on my bodies, they work fine without lens-attached confirmation. No great photography will come of it, but they work .

Poisson Du Jour said:

IIRC through the MIR EOS site, the flange lever plays an important role in diagnostics when, for instance, the EOS 1N is connected to a technical interface via the hot shoe to assess control circuits, lens-body-body-lens communication, focus position, Tv/Av settings, shutter/shutter curtain delay and accuracy, drive readiness, drive wind and rewind cue (build up of tension at frame #36); there are many other checks possible.

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I can see how the flange lever comes into play in the diagnostics area. But how (if at all) is the switch relevant to the actual user?

Poisson Du Jour said:

I imagine that if the switch is not engaged the body will not know a lens is positively attached and lens-body circuits are connected and ready.

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Repeating myself just to be annoying: without the switch engaged my bodies (600, 1N) work fine.

Poisson Du Jour said:

The EOS 600 does not have a system reset (like the 1N, 1V) to clear fault states. I would not attempt to organise the camera yourself at the risk of incurring damage — it's not clear why the mirror is behaving in the manner you described.

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The best reason I can come up with is for diagnostic purposes (access to the front of the shutter on cameras without MLU).

Poisson Du Jour said:

More information (on all EOS bodies) can be found on the MIR EOS site (I am a contributor to this very large resource project): http://www.mir.com.my/rb/photography/hardwares/classics/eos/EOS-1n/htmls/MapEOS1n.htm)

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No reference to the switch on the nomenclature map (http://www.mir.com.my/rb/photography/hardwares/classics/eos/EOS-1n/htmls/MapEOS1n.htm) nor on the in depth AF page (http://www.mir.com.my/rb/photography/hardwares/classics/eos/EOS-1n/Focusing/index2.htm).

Relevant info on the switch may be on that site, however I can't find it. No easy searching with such generic terms as AF, switch, lever, flange, etc. .

Sorry to come across a bit unconstructive perhaps, Poisson du Jour, that's not my intent. I just seem unable to make any sense out of this switch at all.

I have never got my EOS 1N or 5 to fire without a lens on! :confused: You can do some cruel and unusal things (which I won't discuss!!) to EOS bodies to make them hang (and thus need to invoke CLEAR or CLEAR ALL on the 1N, 1V!!).
That's not going to see me poking around to see how things work!!

AND, there's nothing unconstructive about your post. I get very frustrated with the MIR site. The informative it contains is very, very, deep, as you might gather, and not really helped by fractal English. Even good ol' emails are lost on them occasionally. The site authors are (predominantly) Malay / Canadian / US and Chinese (a lot work in IT full time, play with cameras the all other times) with a medley of global hangers-on (real photographers), and those guys are extremely 'switched-on' from literally dismembering bodies — camera bodies I mean, in the search for truth!) and the site does not ~ years after it first came into being ~ yet have a generic search engine. I get lost in it myself and have great difficulty finding those parts I have contributed to — text, and images... I don't really care and in truth, neither do they. They make dream-like money in IT!!

I don't think it (the switch) is of any relevance whatsoever to the average user. Why should it interest Mr. Snapper? You must be the first person on APUG to have raised the issue. What else is there? For now, put the toys away and go back to bed!!

lxdude said:

While you're there, ask if that flux capacitor ever needs any maintenance.

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Mine has never needed maintenance. I just stuff in a banana peel every few years.

sandermarijn said:

Both my EOS 600 and 1N fire without lens, in all modes (PASM).

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Ditto. EOS 1N, 1N-RS, 1V, 3, my former Elan 7N and EOS 1, and three RTs, they all act the same. Fire with or without a lens, doesn't matter what the camera settings are.

Sander, you remind me of me! Little things like this drive me completely insane. I can't help you with your question, unfortunately. The thought did cross my mind that the lever might have something to do with the original Canon FD to EOS converter/adapter, but that doesn't really make sense.

P.S. I'm excited for 2015; Back to the Future Pt. II takes place that year (partly).

LJSLATER said:

P.S. I'm excited for 2015; Back to the Future Pt. II takes place that year (partly).

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I'll be looking out for a young healthy Michael then. Can't help going all sentimental when I see him on TV nowadays. He was so wonderful in BTTF. Great guy, so enormously brave.

Thanks for identifying with my little quest, it's good to know I'm not the only moaner .