About the AFMA problem: Canon lists it in the description of the 1.2.1 firmware update as follows:
13. Fixes a phenomenon in which the camera changes the AF microadjustment value to -8.
I have had this problem and since sharp images are mission critcal for me I cannot go back to 1.1.3,
which is of course just my personal problem.
In two German forums with a total of 350.000 registered users a number of people have reported
two phenomena, that are immediately linked to up/downgrading firmware.
1) After the upgrade 3rd party batteries that previously worked have been refused.
Some report the batteries not working at all, others (like me) report the camera asks for
permission to use these batteries and then worked like it should. Some of those with
cameras that refused the batteries could not heal the problem by downgrading again.
2) Some People who did not have the AFMA -8 problem before upgrading had it after
downgrading. Given, there is a chance that they did have it but did not notice before.
Canon also states in the firmware upgrade descripion:
Notes:
･ Once the EOS 5D Mark III camera is updated to version 1.2.1, it cannot be restored
to a previous firmware version (Version 1.0.7 through 1.1.3).
They also mention a firmware revision 1.2.0 that was never rolled out as
standalone upgrade but obviously part of factory revision deliveries.
My theory now is that there have been silent hardware upgrades and they
have found a way to make 1.2.1 work on all hardware revision platforms.
Theory 2 is that there might be different versions of 1.1.3 firmware out there,
and downgrading to the standalone upgrade will cause problems on bodies
that have been shipped with a later silent hardware upgrade that included
an upgrade to 1.1.3 without a change of firmware revision numbers.
So - being able to downgrade to the standalone firmware 1.1.3 does not
necessarily mean that this is problem free. One might end up with a body
that has a silent hardware update running a firmware revision that was
written for a body without that update.
I might be wrong on all this, but why should people make up their reports?
Obviously their cameras display a different behaviour with firmware 1.1.3
after up/downgrading to Firmware 1.2.1 and back to 1.1.3. Which in turn
must mean that there must be different versions of 1.1.3, or 1.2.1 changes
things during the upgrade that are untouched by the downgrade.
However, this is too much uncertainty for me.
Please understand that I am not trying to bug anybody or push anybody
towards anything. I want to help, and I can wait for whatever comes our way,
ML 2.3 stable runs fine on my 5D MkII. It's just that the 5D MkIII sees little
video work for lack of a working ML on firmware 1.2.1.
But again, that is my personal problem, not yours. The main part of my work
remains photography, and AFMA -8 does not help that too much.
I appreciate your work, and I am a happy camper with the 5D MkII and 2.3 stable.
