I set (Menu F5) to AF Lock only. If I compose a picture and press the shutter release halfway focus is achieved and I see the little green focus circle on the bottom left of the viewfinder. However if instead of pressing the shutter release, I press the AE/AL button, nothing happens and I don't see the green circle. Am I missing something?
With f5 set to AF-L you would first acquire focus by pressing the shutter until the green dot appears. Then you would press the AE/AF button and the green light will show which means the focus is now locked. Then press the shutter release button. If f5 is set to AF-on (many prefer to activate focus with this button), pressing the shutter would have no effect on focusing but pressing the AE/AF will now become the way focus is achieved. Once focus is correct (green dot) you press the shutter button. So it depends what you want the buttons to do on how they should be set. I really like having AF-on assigned to the AE/AF button.
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AF-On is very useful for most subjects but using AF-C focusing mode eliminates the AF assist light from firing. Other than that, everything gets easier to control using the AE/AF-L button as AF-On. I add one more step which is changing the function of Fn to AE-L. That way, I can control AF plus AE locking with thumb and middle finger without moving my index finger on the shutter release. AE-L is essential when recomposing to maintain the metering value initially read. It makes spot metering quite a bit more useful. This is even more important with FX due to the concentration of FPs in the center of the frame means more situations were you need to meter, focus and lock to recompose instead of relying on focus points that do not cover much of the frame. I find the AE-L button(Fn)on the front of the camera more natural of a button location than on the back, needing more of a stretch for the thumb to activate it. It is central to the grip area so is just as easy to reach in horizontal as vertical orientation. Stan St Petersburg Russia
I have my AE-L/AF-L button set to AF-On. Am I right in believing that once I've focussed using the AE-L/AF-L Button I don't need to keep it pressed to maintain focus (as the depression of the shutter release won't then activate focussing)?
Yes, when the button is released, AF stops. So my keeping the mode in AF-C, you have the choice of the Single Servo action or Continuous AF based on whether you tap the button or hold it down. For focus and recompose it is very handy. Adding the AE-L function to Fn button allows full control of both start and stop of focusing and metering and shuter release become solely releasing the shutter. Once you get used to it, you will not go back. It will be second nature within 25-50 frames. Stan St Petersburg Russia
Thanks Stan. That's very useful information regarding AF-C function. At the moment I'm using mainly AF-S but I need to think about that more bearing in mind what you've just said. At the moment I've got the Fn button allocated to Bracketing Burst and I've also just set the Preview button for Bracketing burst as well. This latter allocation for the Preview button has only been done today as a result of me receiving (today) a Meike Battery Grip. I've found that in the portrait position the Preview button falls to hand for Bracketing burst better than the Fn button. As to the AE-L function... I'm shooting exclusively in manual so resetting of exposure isn't a problem but again, thanks for the advice.