I would like to separate exposure from the shutter button and lock exposure.I tried the following:- AEL Button: AF ON - AF/MF: AF/MF Toggle - AF w/Shutter: OFFLever in up position and pressing center button, will enable selecting AF/MF;Lever in down position (AEL) will enable focus and exposureBut I would like to simultaneously lock exposure temporarily until I have shot the picture.How can I achieve this best?Thanks for advise!