Thanks I was afraid of that I have to push the iso button first
and can't assign the ISO button to the front FN button either
There is a note that matrix metering isn't accurate with non CPU lenses so I switched to center metering and it seems a bit more accurate. It takes me several shots to get a good exposure kind of a waist
You could also try setting Custom Function b5 to "Average". Non-CPU lenses all use the 12mm centre weighted diameter unless set to "Average". Maybe that will improve your results (it will likely at least change them!).
BTW, you can quickly toggle from one metering mode (i.e.: matrix) to another without using the dedicated (and hard to turn) switch on the back of the camera by setting the front fn button to your alternate meter (i.e.: leave the metering switch in matrix and assign the fn button to centre weighted). As long as you hold the fn button, your "alternate" metering mode will be active. I use this sometimes to toggle from matrix to spot without having to take my eye away from the viewfinder.