Help me understand this webpage about back-button focus

[mathbias]

Are You Using This Essential Autofocus Tool?

See why pros use back-button focus and how to set it up the right way on your Sony camera

alphauniverse.com

I have my Sony a7 iii set up a different way for back-button focus (thanks to this forum telling me it is called "back-button focus").

But the above web page seems to describe a better (and very different) way to get back-button focus. I didn't get expected results when I tried it. Likely because I misunderstood what to expect. But maybe because I missed a detail in configuring the interacting settings.

The part I think I need to understand is where it says:

to autofocus, simply press the button to which you’ve assigned AF/MF Control Hold and click.

I don't know what "and click" means.

This system has the camera in MF mode, which is great if you can AF on demand in MF mode.

Then some action lets you AF (at whatever you were pointing at when you do that action). That action is then done (that is important); you don't need to hold anything from then on through reframing and taking the photo. As long as you don't touch the focus ring after doing that, you remain focused at that locked in distance even though you are back in MF.

It would be great if that action were just pressing the button you configured for this feature, holding it until you like what the AF has selected, then releasing it. That is how the other form of back-button focus works for me. If this setup should do that, I've configured something wrong, because it didn't act that way.

Maybe it means press and hold this button, then with it held press and hold the shutter half way, then release both. That seems a better fit relative to the way the camera documents the interacting features. For someone with normal dexterity that is nearly as easy as a single button action. For me it would be much harder. Maybe the flexibility of this back-button scheme compared to the other will make it a better choice despite being more difficult. Before I go too far down that road, I want to to if I can have the best case by just setting the right interacting setting correctly.

 

[NS: Nikon Shooter]

-

The greater advantage of the BBF approach is well over priority
aperture or SS, it moves the priority to focus.In this, it will not in-
terfere with the "usual" priority modes.

 

[Strodav]

Out of the box, if you press the shutter button down half way you engage the camera's AF system. BTW, "click" means pushing the shutter button down all the way to take a picture. Your camera's AF system has two major modes: 1) continuously refocus when the shutter button is pressed halfway down right up to the click; 2) once focus is achieved lock focus where it is and don't change it until the "click" or you let up on the shutter button. Mode 1 is generally used if your subject is in motion. Mode 2 is generally used if your subject is still and has the advantage that once focus is locked, you can reposition your subject in the frame for composition purposes and not loose focus on the subject. We are going to skip over how many focus points to use and different tracking modes to keep it simple.

BBF is the best of both worlds without having to change camera settings. First, you need to turn off AF when the shutter button is pressed down half way. When you push the shutter button down 1/2 way, nothing happens. When you push the shutter button down all the way, you capture the image. You'll have to go through your cameras menu system to do this. Next you need to assign the AF function to another button, again using the camera's menu system. Third, you need to set the AF mode to continuously refocus. So, when you push your chosen button, you active AF and it will continuously refocus as long as you are pressing the button, which is generally used when your subject is in motion. When you let up on your chosen button, AF will stop staying locked where last focused was achieved so you can re-frame if you want

My nature/wildlife bodies are set up for BBF. When my subject is moving, I keep pressure on my AF button so the camera is continuously refocusing on my subject as it moves right up to click. If my subject is still, I engage AF to lock on the subject, let off my AF button as focus is locked, then re-frame if necessary before clicking the shutter. Hope this helps.

 

[mathbias]

The greater advantage of the BBF approach is well over priority
aperture or SS, it moves the priority to focus.In this, it will not in-
terfere with the "usual" priority modes.

You lost me 100%

I would have thought choices like priority aperture would be entirely independent of BBF.

I have a button that works the way I want for locking in the result of exposure metering. I aim at an appropriate point, then press the AEL-toggle button and the result (mode dependent) of metering is locked in based on that spot.

I use mostly priority aperture mode, so I select aperture, then I press AEL-toggle so the camera selects shutter speed and ISO and displays them on the monitor.
I also might use M mode (because that is practical to use, unlike M mode on the Canon sx530 I had been using). I have that set up so that I select both aperture and shutter speed, then use AEL-toggle to get the camera to select and display ISO.

All that happens before I start to focus. I then aim somewhere else: some high contrast spot at the distance that I want to focus. (That is typically neither the spot I chose for metering nor the spot I will choose for the center of the shot). Then I press the button that shows a high digital zoom in the monitor (digital zoom only affects the monitor, not the photo that will be taken). Then I press the BBF button and see that zoomed image come into focus. Then press that digital-zoom-for-focus button again to go back to normal view.

Finally I can aim where I actually want the picture centered and press the shutter button.

I'm open to suggestions on the overall process. I know I'll need a very different process for capturing subjects that aren't stationary long enough. But stationary first in my learning process.

For the thread I started here, I am looking for how this alternate method of configuring BBF (as described on that web page) works, since I haven't managed to get it to work.

 

[NS: Nikon Shooter]

You lost me 100%

Sorry for that!

I was trying to help very carefully you even if I don't know
anything else but D Nikons and you are on Sony.

 

[mathbias]

First, you need to turn off AF when the shutter button is pressed down half way. When you push the shutter button down 1/2 way, nothing happens.

That is the key aspect of the difference between the BBF as I have successfully used it and the maybe-better BBF described on the page I linked.

IIUC, that web page has told me not to turn off the option for AF when the shutter is half pressed. The half press will do nothing, but for a different reason.

But I don't fully understand that setup.

BTW, "click" means pushing the shutter button down all the way to take a picture.

That is exactly what I both guessed and hoped when I read that in the web page. If it means that then the way it should work is the way I would want it to work. Since it doesn't work as expected, I should experiment with combinations of relevant settings until it does.

Third, you need to set the AF mode to continuously refocus. So, when you push your chosen button, you active AF and it will continuously refocus as long as you are pressing the button, which is generally used when your subject is in motion. When you let up on your chosen button, AF will stop staying locked where last focused was achieved so you can re-frame if you want

My nature/wildlife bodies are set up for BBF. When my subject is moving, I keep pressure on my AF button so the camera is continuously refocusing on my subject as it moves right up to click. If my subject is still, I engage AF to lock on the subject, let off my AF button as focus is locked, then re-frame if necessary before clicking the shutter. Hope this helps.

I hope I someday have the skill to use this camera that way. I never had ordinary manual dexterity, and now that I'm older I have even less.

So for stationary subjects, the single AF is easier. the camera vibration as I release the AF button won't wreck the focus I was trying to capture.

For non stationary subjects, maybe I'll have enough dexterity for your way. Maybe I won't. Maybe I will need to dump the idea of focusing separately from framing, and use the camera in its more basic mode of press the shutter half way down and let the camera make the choices.

 

[weepete]

I think if you make sure any pre-focus is off, then assign the AF with shutter to off, then assign whatever custom button you like to AF On this should be the classic back button focus. You'll maybe need to turn the focus mode back to AF.

I think the web page you've looked at gives a kind of hybrid style to toggle on and off both. Not fully certain as I don't use Sony, but may be worth giving it a shot.

I much prefer back button focus.

 

[Strodav]

That is the key aspect of the difference between the BBF as I have successfully used it and the maybe-better BBF described on the page I linked.

IIUC, that web page has told me not to turn off the option for AF when the shutter is half pressed. The half press will do nothing, but for a different reason.

But I don't fully understand that setup.



That is exactly what I both guessed and hoped when I read that in the web page. If it means that then the way it should work is the way I would want it to work. Since it doesn't work as expected, I should experiment with combinations of relevant settings until it does.



I hope I someday have the skill to use this camera that way. I never had ordinary manual dexterity, and now that I'm older I have even less.

So for stationary subjects, the single AF is easier. the camera vibration as I release the AF button won't wreck the focus I was trying to capture.

For non stationary subjects, maybe I'll have enough dexterity for your way. Maybe I won't. Maybe I will need to dump the idea of focusing separately from framing, and use the camera in its more basic mode of press the shutter half way down and let the camera make the choices.

It just takes practice. It’s all about t.o.t.; Time on task. The more you do it the better you will get at it. I’m 70, very average physically with arthritis, mostly using a Nikon D850 or D500 with a heavy Nikon 200-500mm f/5.6 zoom, sometimes with a 1.4x Tele converter mostly handheld for bif. I can handhold my 600mm f/4G (nicknamed Behemoth), but almost always use it on a tripod with gimbal.