photodoc16 wrote:
I was about to convert my 7DII to BBF when I watched a video that mentioned, on this camera, you could not separate the focus from the metering function. Is this true and, if so, how to these two functions interact?
Thank you, Hogs
Photodoc16
It's super easy to set up BBF on 7DII... That video is incorrect.
In fact, with the factory defaults BBF is basically already set up. The AF On button on the rear of your camera, under your thumb, will start auto focus. But so will a half-press on the shutter release. So to truly "do BBF", all you need to do is go into the button assignment/customization menu and
disable AF at the shutter release button. The shutter release setup the very first item under on that menu page and once you've navigated to it, simply change it to the middle setting (I think it's labelled "Metering").
Done. That's all there is to it. You're now "doing BBF".
In fact, metering (and image stabilization) will still start
either when you half-press the shutter release
or when you press the AF On button on the rear of the camera. That's fine and what you normally will want the camera to do.
It can sometimes be desirable to do, so if you want the camera to stop metering and changing the settings when in the auto exposure modes, use the separate AE Lock button, which is right next to the AF On button.
One of the primary reasons to use BBF is to be able to use AI Servo as your default focus mode setting, with both stationary and moving subjects.
Without BBF, there are times when AI Servo can be a problem, such as if using a "focus and recompose" technique. With BBF enabled, you activate AI Servo AF by pressing the button with your thumb and once focus is achieved on a stationary subject, if you want to recompose, lift thumb pressure off the button so that focus remains set on the subject and recompose as you see fit.
Having the camera in AI Servo mode all the time and using BBF lets you be ready for anything... moving or stationary, focusing & recomposing or not.
One advantage to AI Servo is that many zoom lenses today are varifocal, meaning they don't exactly maintain focus when you change the focal length setting. If you are using One Shot, you have to remember to stop focusing and restart it after any zooming. If you are instead using AI Servo, it will automatically and instantly correct the focus is the lens doesn't maintain it when zooming.
If you use Spot Metering, keep in mind that it sn't linked to the active AF point. It remains at the center (as defined by an engraved circle on the focus screen) on the 7DII, as with most Canon cameras.
However, if using Evaluative, the metering will put extra emphasis at your active AF point(s), sort of assuming that's the primary subject and most important part of the image area to meter.
This is similar to, but not exactly the same as AF-linked Spot Metering (which 1D-series cameras have, though it is limited to a reduced number of AF points in some models).