adding AFMA feature (Rebel)

[JoaquinS]

Hi, I'm new to the forum, found that searching to ad AFMA to my T5i, since I got a new fast lens and it misses focus by a few mm and that's enough to focus on the nose instead of the eyes.

I haven't found anything, but programming for this kind of devices is one of my skills from my degree and some of my day jobs. If there already is something please let me know.

I haven't decided yet if I'll go with a module or a Lua script, the later seems simple enough, but I'm more familiar with C and as something running continuously in the background seems a better choice.

First goal would be a program to set it manually, single point correction to test the procedure, second to search to build a table for lens, focal length and focus distance and the module choose from there, all editable in camera. The last step would be some sort of calibration assistance or automation, but as something that you do once and forget, even if painful to do, making the module just for me won't be likely to happen, maybe if there's enough interest it could be added later.

The idea would be to use the autofocus function (in viewfinder mode) and then make n steps back or front to correct for the error stored in the memory.
For the second part, start reading the lens signature, then the focal distance and finally do the focusing as in the simple version, but this time choosing the right value from a table corresponding to lens, focal length and focus distance.

Any feedback appreciated, I make this post to introduce myself, to put the idea out and see if there's something I'm missing before starting doing something that's already been made.
Thanks.

JS

[JoaquinS]

  Few updates, rough days around here...

  So far I can say I think it can't be made as a script, as they only work in live view and that's not what I'm interested in so I started setting up to compile ML on OS X and after some fiddling around I got it working thanks to a script from another user. After that haven't found the time to do it, I need it to work eventually as I have this 70-200 that will back focus at 2.8 pretty noticeably.

JS

[a1ex]

Outside LiveView, autofocus is done exclusively on the MPU (including the decision to perform AF, in which direction and so on).

In LiveView, the main CPU has some control: it can ask the MPU to move the focus ring (by requesting a number of steps, a certain speed and so on). The MPU refuses to interpret these commands outside LiveView, so this approach is not going to work for AFMA.

https://www.magiclantern.fm/forum/index.php?topic=4997.0
http://www.magiclantern.fm/forum/index.php?topic=17596.0

To implement this, one needs to reverse engineer the MPU firmware.

[JoaquinS]

Outside LiveView, autofocus is done exclusively on the MPU (including the decision to perform AF, in which direction and so on).

In LiveView, the main CPU has some control: it can ask the MPU to move the focus ring (by requesting a number of steps, a certain speed and so on). The MPU refuses to interpret these commands outside LiveView, so this approach is not going to work for AFMA.

https://www.magiclantern.fm/forum/index.php?topic=4997.0
http://www.magiclantern.fm/forum/index.php?topic=17596.0

To implement this, one needs to reverse engineer the MPU firmware.

Ok, I see why nobody did it then... Thanks!

As I understand, Canon does perform focus calibration on this bodies in some way, if you send the lens and the body to them, does someone here know how they do it, if it's possible to do it without shipping all the kit to them?

JS

[Sapporo]

Ok, I see why nobody did it then... Thanks!

As I understand, Canon does perform focus calibration on this bodies in some way, if you send the lens and the body to them, does someone here know how they do it, if it's possible to do it without shipping all the kit to them?

https://www.spt.info/sptstore.php/canon-eos-700d_t5i_kiss-x7i/software-canon-eos-700d-advanced

[JoaquinS]

https://www.spt.info/sptstore.php/canon-eos-700d_t5i_kiss-x7i/software-canon-eos-700d-advanced

Thanks for that! I hadn't seen that in all my search...

JS