5 mk2 custom functions

[marky.b]

I recently upgraded from 5 d to a 5 d2
I also bought an excellent book by David busch, mich better than magic lantern abd digital field guides
However on p247 ch8 the custom function section, it mentions
C.fn 111-02 function of the af stop button on certain image stabilised lenses
It says that if u have an upper echelon IS lens
This function is for you if u don't gave one then skip this section
What is a upper echelon lens

 

[digitalfailure]

Some of the larger "more costly" L series super telephoto lenses have this function

 

[marky.b]

Some of the larger "more costly" L series super telephoto lenses have this function

Is the 100-400l one of these
I was at airshow on Sunday and had a bit of problem focusing
I was using IS mode 2 and ai servo
For some reason focus was a bit off
I m still learning this model
I had a look in this menu and I changed to af start , it was set to disabled
After that focus was much better