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sally forth May 27, 2010 10:42 AM

a850 focus lock
Am trying to figure out controls on a new a850. How can I lock focus and recompose image without holding down a button? Is full manual focus the only way? I shoot on a tripod with a wireless remote on 2 sec. delay to minimize vibration.

JimC May 27, 2010 10:59 AM

1 Attachment(s)
Welcome to the forums, and Congrats on the new A850. It's a fine camera.

If you look in your custom settings menus, you'll find settings that let you customize how the AF/MF button on your camera works.

Basically, change the first choice labeled AF/MF button to "AF Lock" versus the default "AF/MF control" setting.

Then, set the next menu choice on the page labeled AF/MF Control to "Toggle" versus the default "Hold" setting.

That way, it should lock focus when you press the AF/MF button, and unlock it when you press it again. That should let you lock focus with a half press of the shutter button as you're doing now, then press and release the AF/MF button so that the focus distance will stay locked.

The first two choices on this screen are the ones you'll want to change (with this screen capture showing the default settings versus the ones you'll want to use so that the AF/MF button locks focus when pressed and released):

sally forth May 28, 2010 9:57 AM

Thanks for the info, however camera still refocuses when I shoot. Also contacted Sony support and a camera retailer. Both said only manual focus will allow me to focus on a subject, re-compose image and shoot without holding down a button.

JimC May 28, 2010 11:12 AM

Interesting... You're right (not working the way I thought it would).

One other way to approach it would be to leave the AF/MF control button set to the default AF/MF control. Then, change the AF/MF Control choice to Toggle versus Hold so you can switch to MF by pressing the AF/MF button after locking focus using AF (then, you'd see MF in your viewfinder after pressing it).

That appears to work without changing focus distance from what I can tell from a quick test with my A700 (which has the same AF/MF button and settings choices), even though I can hear the AF drive disengaging.

That would allow you to focus using AF with a half press, then release the shutter button and press the AF/MF button switch to switch to MF, which disengages AF. Then, reframe as needed and take shots as desired until you need AF again so you can refocus (just press the AF/MF button to switch back to AF).

IOW, just set the AF/MF button to Toggle between AF and MF, still using AF to focus before switching to MF to reframe and take your shots.

sally forth May 28, 2010 12:56 PM

That may be a solution. Tried a couple of quick shots and will experiment more over the next few days. Thanks.

Furd May 28, 2010 11:33 PM

AF/MF toggle
Maybe I don't understand the problem.
I have a 900 and it works as described in the manual.
With AF/MF in toggle position and set to MF and focused on an object, it will remain focused at that distance, shot after shot, recompose after recompose, unless manually changed.
It will not auto focus until AF/MF is toggled back to AF. This may not be a very good explanation of how the 900 works, but I like it and find it really useful. I have small hands and find it awkward to try and keep the AF/MF button press while recomposing.
I'm wondering is Sony support and the camera retailer had a clear understanding of the problem encountered.
After another reading of JimC response, I guess that is the way I do it.
I will be interested in the outcome.

Furd May 28, 2010 11:55 PM

more AF/MF
The word "HOLD" may be misleading, I think it means you must "hold the button, keep pressed" until the shot is complete, recomposing during "hold" will not change the focus automatically

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