Metering with back button AF

Hi

I got used to using back button AF in my sojourn with Nikon and on my mk2. I just want to check I have the right idea of how it works with the 5D mk3.

Here's my understanding.

If I set the AF button to the "metering and AF start" option in custom settings this means that the AF button will start AF. I can either choose to release it or hold it down ( if using servo mode it will continue to track focus )

If I have the shutter release button to "AE stop" when I press this metering will lock while I hold the button down. If I have it set to "metering start" it will continue to change when I point the camera to another area. ( AE lock being especially useful for using eg spot metering in backlit situations etc )

I assume this is correct but if I don't understand it properly I'd be grateful for any corrections.

Anyway, here's my questions.

1 Does the AF button have any input into metering at all in the circumstances I describe above and if so does the shutter button override metering so I can forget about it?

2. If I keep the AF button pressed will this continually update exposure too? How does it fit in with the shutter button exposure reading?

3. What part does the selected focus point play with the above settings?

I'd be grateful for your help.

W

Having played around a bit today I believe I was right in what I said above. If not, I'd still be grateful for any advice or guidance.

willie45 wrote in post #16171765
Hi

I got used to using back button AF in my sojourn with Nikon and on my mk2. I just want to check I have the right idea of how it works with the 5D mk3.

Here's my understanding.

If I set the AF button to the "metering and AF start" option in custom settings this means that the AF button will start AF. I can either choose to release it or hold it down ( if using servo mode it will continue to track focus )

If I have the shutter release button to "AE stop" when I press this metering will lock while I hold the button down. If I have it set to "metering start" it will continue to change when I point the camera to another area. ( AE lock being especially useful for using eg spot metering in backlit situations etc )

I assume this is correct but if I don't understand it properly I'd be grateful for any corrections.

Anyway, here's my questions.

1 Does the AF button have any input into metering at all in the circumstances I describe above and if so does the shutter button override metering so I can forget about it?

2. If I keep the AF button pressed will this continually update exposure too? How does it fit in with the shutter button exposure reading?

3. What part does the selected focus point play with the above settings?

I'd be grateful for your help.

W

Not sure but on my 7D, it seems that with AF-ON set for BBF, the "metering start" is triggered not by the AF-ON button but still by the half-press on the shutter. The focus point doesn't really play into the metering. The metering is based on the metering mode you choose - either spot, center-weighted, or evaluative, etc. The spot meter uses the center spot.