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A77 AF/MF feature

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William Porter

William Porter

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I don't think I understand the AF/MF button's purpose or use on the A77 and I'm hoping somebody can enlighten me. I have read (but perhaps not understood) the pertinent pages (126, 137, 177) of the user manual.

I have my A77's focus mode dial (on the front) set to S. The 16-50/2.8's AF/MF switch (on the barrel) is set to AF. If I depress the shutter half way, the lens focuses, as expected. But I can also, at any time, grab the focus ring and focus manually. I can hit the button for focus magnification, zoom in, and focus carefully by hand. Without adjusting the autofocus mode dial or the switch on the lens.

And it doesn't seem to matter whether I'm touching or have touched the AF/MF button. Actually I have reconfigured the AEL button to "AF/MF Control Hold." (I did this because I want the AF/MF button to do focus magnification, which I use a lot. Hope this isn't too confusing.) Anyway, as I understand it, AF/MF Control Hold OUGHT to mean that, to focus manually while the camera and lens are set to autofocus, I would have to depress that button and hold it down.

But that button doesn't seem to make any difference at all.

What am I missing here?

Will
 
The AM/FM button will toggle focus peeking if you have it activated. I have my AEL button set up for focal magnification and left the AF/MF button on it's original setting.
 
The 16-50f2.8 is equipped with DMF(direct manual focus)so you can manually overide autofocus at any time without having to switch to manual focus.So in this case the AF/MF button is redundant.But ,not all lenses have DMF.That's when this button becomes more useful.Hope this helps.
 
William Porter said:
I have my A77's focus mode dial (on the front) set to S. The 16-50/2.8's AF/MF switch (on the barrel) is set to AF. If I depress the shutter half way, the lens focuses, as expected. But I can also, at any time, grab the focus ring and focus manually. I can hit the button for focus magnification, zoom in, and focus carefully by hand. Without adjusting the autofocus mode dial or the switch on the lens.
Click to expand...
Yes, because SSM lenses are an exception and allow you to use the focus ring manually at any time.
William Porter said:
Anyway, as I understand it, AF/MF Control Hold OUGHT to mean that, to focus manually while the camera and lens are set to autofocus, I would have to depress that button and hold it down.
Click to expand...
Exact, but only with screw-drive lenses.

AF/MF still makes sense with SSM for one thing, if your lens and camera are set to AF, pressing the AF/MF button will acivate peaking (if you have it enabled of course). It can also be useful in the opposite way, if he camera or lens is set to MF then pressing the button will do a one-shot focus.

SAM lenses can do nothing of that, and require you to always move the lens' switch to change between MF and AF.

--
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Clint501 said:
The AM/FM button will toggle focus peeking if you have it activated.
Click to expand...
This is a huge benefit if you have DMF and can remap this button to focus peeking. Was at the zoo this weekend shooting pics through a lot of fences and what a great feature to just press this button to see where focus is at and then quickly turn the focus ring if need be. Truly a great feature.
 
Glenn said:
you weren't really wrong, the effect is the same it's just you should be aware of what DMF is as a setting on the body.
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Glenn, I get the general idea now (thanks to everybody) but I'm still a little confused about this detail. You saw DMF is "a setting on the body." I assume you're talking about the AF-A Setup option on page 3 of the camera menus. But I have my body set to AF-A (not DMF). And for what it's worth the focus mode switch is set to S.

At the moment it SEEMS like the 16-50/2.8 SSM is like a few of the old Pentax lenses I used to have, that had a feature whose name I can't recall. I'd describe it as autofocus focus manual fine-tuning. You'd autofocus, then turn the focus ring slightly to tweak it. If that's what the 16-50 is doing, well, that's nice. But I still don't see how any setting on the body is making a difference. So it looks to me like a lens capability alone. What am I missing now?

Thanks,

Will
 
I have set the AF/MF button so it toggles between AF and focus peeking. Pushing down the joystick in AF gives me center spot focusing. I programmed the AEL button to give me Focus Magnification and left the Smart Teleconverter button to its default function as well as the ISO button. This setup suits my type of shooting quite well.
--
  • Happiness is: Sony SLT-A77 / Rokinon 8mm / Sigma 10-20, 18-250, 50-500mm - Karl
 
OK, thanks, I've almost got it. What I obviously need to do is take the 16-50 off the camera and see how it all works with my other lenses. Will give that a try.

Anyway thanks again to Glenn and everybody else for solving this mystery quickly — and to my mind, happily. I was worried for a second that something was broken...

Will
 
dennismullen said:
I am missing this feature on my A65. :(

Cheers,
--

"Those who would sacrifice liberty for safety deserve neither liberty nor safety." - Ben Franklin.
You can see larger versions of my pictures at http://www.dennismullen.com .
Click to expand...
The AF/Mf button is the primary feature that kept me with Minolta when they introduced it on the Maxxum 7. With a long lens I was having a very difficult time locking on small moving subjects (BIF), or subjects mixed in with other "stuff". The photo below shows one such example - a Blue Heron behind some reeds. The bird was moving so I wanted to use AF-C, but the camera kept locking on the reeds in the FG. I used the AF/MF button and manually prefocused on the bird. I placed the Af sensor I selected over the bird's eye and then released the button. The camera made focus, and I was able to track the bird until I liked the composition (in this case it was when the bird moved so the thick reed (out of focus) was off of its face.) Then I released the shutter.





I had been looking to change from Minolta to Canon because their USM lenses would allow this whereas the Minolta cameras before the 7 did not (switching to manual focus, prefocusing manually, and the reengaging AF-C resulted in the camera resetting the lens to infinity, making prefocusing impossible.)

It's also the reason why I have absolutely no interest in any Sony camera below a 7 series.
 
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