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a55: Changing Focus/lock to back button

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Takaa View Drop Down
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Post Options Post Options   Quote Takaa Quote  Post ReplyReply Direct Link To This Post Topic: a55: Changing Focus/lock to back button
    Posted: 29 August 2010 at 16:13
I'm looking at the manual for the a33/a55 http://www.docs.sony.com/release/SLTA33.pdf and am trying to figure out if it's possible to program one of the back buttons (presumably the AEL) to perform focus/lock instead of the traditional shutter half-press.

This is something that I've be able to do for years with other SLRs; it was taught to me by a photojournalist who showed how it was faster to punch a back button to lock exposure then be able to lift your finger and just wait for the right moment to shoot at a pre-focused area (instead of having to keep a poised, half-pressed shutter). It's second-nature to me and it's something I need in a camera, and this button-reprogramming is in most Canons and Nikons.

The Sony a55 manual shows how you can change AEL hold as either a hold or toggle, but I don't see anything about changing the focus from the shutter to another button. Am I missing it or is it possible but left out of the manual ... or is this just not possible on the a55?
 



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sybersitizen View Drop Down
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 16:25
Originally posted by Takaa Takaa wrote:

... or is this just not possible on the a55?

I believe that is the case.
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Takaa View Drop Down
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Post Options Post Options   Quote Takaa Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 16:34
Ugh. I shoot a lot of street photography and I need to be able to quickly set up a focus area then wait a bit before shooting, then be able to set up another one. Manually focusing would just be too slow, and I just can't hold my index finger at half-press for numerous sequential dozen-second periods over the course of a day.

Sadly, if this is true it is a real deal-killer for me and I have to look at other cameras/brands.
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sybersitizen View Drop Down
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 16:40
Sounds like you could autofocus on what you want, then switch to manual focus using the side switch. The focus will then be 'locked'. Switch back to autofocus and repeat as necessary. I do that a lot.
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Post Options Post Options   Quote Bluemoose Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 17:01
My a200 allows me to focus using the five buttons of the directional pad, and using "local" focussing mode, actually allows me to pick which sensor point it uses. With the shutter set to release priority, I can pre-AF using back buttons and then pull the shutter later, much as you describe.

I would be surprised if the a55 didn't have this functionality.
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Takaa View Drop Down
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Post Options Post Options   Quote Takaa Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 17:02
sybersitizen, it's doable but rather kludge-y from shot to shot:

  • half-depress with right hand
  • lens switch-off with left hand
  • shoot
  • lens switch-on with left hand
  • half-depress with right hand
  • lens switch-off again with left hand


I think I've been spoiled.





Edited by Takaa - 29 August 2010 at 17:02
 



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Takaa View Drop Down
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Post Options Post Options   Quote Takaa Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 17:10
Originally posted by Bluemoose Bluemoose wrote:

My a200 allows me to ...can pre-AF using back buttons and then pull the shutter later, much as you describe. I would be surprised if the a55 didn't have this functionality.


The manual discusses using the Fn key for selecting focus area and autofocus mode, but not for pre-AF. I can only hope that the manual (or I) missed something....
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de0602 View Drop Down
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Post Options Post Options   Quote de0602 Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 17:15
Unfortunately, in this respect the Minolta/Sony approach differs from other brands but it is still possible to do.

As already mentioned, you could use the switch on the left side of the camera. With the new SAM lenses, which have a AF/MF switch on the lens, you have to use the switch on the lens.

An alternative is to use a lens with a focus hold button. Pressing the button will stop the camera from changing the focus. This feature is usually found on the higher end lenses (primes and zooms) but also on some older mid-level zooms.

MHohner is a good reference to see which lenses have this feature (check "Lens Button" column)

I have used this feature with good success.

(Note: The high end bodies (a700 and up) do have an AF/MF button on the camera next to the AEL button for this exact reason. Maybe we will see this on a A77.)
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Post Options Post Options   Quote whtchocla7e Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 17:51
Why not use the focus hold button on the front of the camera? It can be assigned as either focus hold or DOF preview.
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Post Options Post Options   Quote kefkafloyd Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 17:51
There's a few ways to skin a cat on this front.

In SLRs that have an AF/MF button (KM 7D, a700, etc), that button generally performs what you're looking for, and there's a custom function to delink shutter from focus.

In the KM 5D, a100, first set of a200/300s and the a5x0 series, the central button in the four-way acts as an AF button. You can press this button at any time when not in a menu to engage AF. Even when the camera's set in MF mode, it'll activate AF. This also incidentally works on the a700, 850, and 900. So long as you get AF with this button, you can activate AF independently of the shutter.

Unfortunately, none of these cameras have a custom function to delink focus from shutter half-press. The a55/33 continues on in this tradition. I don't see why the a33/55's AF button (the central button on the four way) would not activate AF when you press it.

There's an additional wrinkle on the a55 that you can use that AF button when in local focus selection point mode to activate focus point selection. Whether pressing that button in local point selection (as opposed to wide focus or central spot only focus) will activate AF in some way is an unknown at this time.
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Post Options Post Options   Quote Sick Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 18:30
Originally posted by kefkafloyd kefkafloyd wrote:

In the KM 5D, a100, first set of a200/300s and the a5x0 series, the central button in the four-way acts as an AF button. You can press this button at any time when not in a menu to engage AF. Even when the camera's set in MF mode, it'll activate AF. This also incidentally works on the a700, 850, and 900. So long as you get AF with this button, you can activate AF independently of the shutter.

Unfortunately, none of these cameras have a custom function to delink focus from shutter half-press. The a55/33 continues on in this tradition. I don't see why the a33/55's AF button (the central button on the four way) would not activate AF when you press it.


The central button of the four-way pad/joystick always AFs on spot.
And spot only.
But it can be hold and actually deactivates shutter press check for focus.
So you can press, hold, move the camera and instant shutter press.

Looking at the images of A55 on DPReview it is still labeled "AF", so I don't see why the function should have changed ;o)
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Takaa View Drop Down
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Post Options Post Options   Quote Takaa Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 18:38
Originally posted by kefkafloyd kefkafloyd wrote:

I don't see why the a33/55's AF button (the central button on the four way) would not activate AF when you press it.


I'm not familiar with the Sony layout so I checked the manual and you seem to be right. Thanks! In a single sentence in the manual (discussing the Focus Magnifier) it says "If you press the AF button in autofocus mode, the Focus Magnifier function is canceled and the autofocus is activated."

This appears to be a part-solution (?) but it doesn't explain whether the a55 will later try to refocus as I press the shutter button. And it's unclear to me whether it locks focus when I release the AF button or if I have to keep holding it or what....

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Takaa View Drop Down
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Post Options Post Options   Quote Takaa Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 18:45
Originally posted by Sick Sick wrote:

The central button of the four-way pad/joystick always AFs on spot. And spot only.


You mean the center AF point? If so that would be fine.

Originally posted by Sick Sick wrote:

But it can be hold and actually deactivates shutter press check for focus. So you can press, hold, move the camera and instant shutter press.


Okay, so that's not quite the lock-and-let-go I'm used to, but if the camera is holdable with my thumb on the AF button it could be doable for me. Thanks!
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Post Options Post Options   Quote Kiklop Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 18:52
I'm one of those that do not use shutter release button for AF; once one is get used on this is hard to go back especially if such options are well implemented with plenty of choices.

With Sony system we can only partially get what other manufacturer cameras do provide. What we have is in best case what Minolta had more than 10 years ago .. nothing has been improved in this regard (and since requests for an improvement here are really scarce i don't believe it will change at all).

It is not only a matter of having a choice to "disconnect" shutter release from engaging AF or don't have an option to use AF-C except with shutter release half press, but also about having the choice on how metering reacts in such cases (with our cameras different metering modes behaves differently and we can't change this).

This is a topic that has emerged several times in the last couple of years and i always had the impression that most a-mount users aren't aware on how different (or limited if i'm allowed to say it) is in this regard from others.
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