Focus and reframe issue

[MLong]

I hope y'all can help me with this: I focus on my subject, but when I then re-compose my composition, the exposure changes to wherever the focus square moves to. 

I use back-button focus, so my AF-L button is used to autofocus (AF-on).  I have the AE-L button set to AE Lock Only.

If I focus on my subject, then keep my finger on the AE-L button, the exposure does not change when I re-compose.  But, it is VERY clunky to keep pressing the AE-L button while also trying to depress the shutter button.

I have tried setting the AF-L button to AE/AF Lock, but when I do that the autofocus does not work at all. 

Is there a way to just be able to focus on my subject, and have the exposure also locked when I re-compose?

I hope you can offer a solution, as I shoot this way 90 percent of the time.  

Thanks in advance!!!

[bergat]

Try to use shutter button pressed in half to focus and then recompose your composition with button half  pressed

Edited September 23, 2018 by bergat