A700/CZ24-70 focus lock problem/question

[picman]

Hello all,

The A700 has a button on the back (AF/MF) which you can program via a menu to either "AF/MF control" or "AF lock". Similarly the CZ24-70 has a rotary switch on the side which you can set to AF or MF and a button in the middle of the rotary switch which can also be programmed via a menu to either "Focus hold" or "DOF preview".

1. When the back button is set to "AF lock" then holding the button down locks not only the focus but also the exposure.
2. When the back button is set to "AF/MF control" then it switches between AF and MF (either held or toggled also depending on another menu setting).
3. When the button on the lens is programmed to "Focus hold" then holding that button locks both the focus and the exposure.

I find these behaviours strange. There are two buttons (one on the lens and the other on the camera) which are supposed to give you the possibility to hold the focus locked but neither does it without also holding the exposure locked (1 and 3). And in order to be able to just hold the focus locked and not the exposure you have to use method 2 which basically consists of switching from AF to MF and back.

My question is: is this the way it is meant to be or is there something not quite OK with my lens and/or body? If this is the way it is meant to be would you agree with me that this is confusing and might it be worthwhile to let Sony know this?

Thank you for your thoughts, cheers, Bob.

[Javelin]

hi Bob

I'm not near my camera to try this but I think whether the exposure is locked or not depends on metering mode.

[picman]

Hi Javelin,

Thanks for the quick reply. I just went through all the metering methods to verify and as far as I can tell the situation is the same with all of them. It makes no difference which metering mode you are in, the exposure always gets locked together with the focus (using methods 1 or 3.)

Cheers, Bob.

[David Kilpatrick]

The behaviour you are looking for is obtained by:

AF/MF Button - set to AF/MF Control
AF/MF Control - set to Hold

Then when you compose and press the button on the camera, the focus locks by switching to manual only while your finger is on the button; exposure is able to vary with re-composition; when you release your finger from the button AF resumes. Same happens with the lens button on my 70-300mm SSM - focus is effectively held, exposure varies, only while pressing the button.

David

[picman]

Thank you for your reply David.

I can confirm the behaviour you described as far as the button on the camera goes. It is indeed exactly as you described. However as far as the button on the lens goes, with the same settings on the camera, holding that button down will lock also the exposure. So this behaviour is different from your 70-300 SSM lens. Do you think that indicates a faulty communication between lens and camera?

Regardless of this, I find it strange that an item in the menu called "AF lock" would also lock the exposure, because as you have indicated you need to set the AF/MF button not to "AF lock" but to "AF/MF control" in order for it to only lock the focus.

Cheers, Bob.

[David Kilpatrick]

My 100-300mm APO D behaves the same way as your lens - lens button silently (no click) locks the focus while depressed, exposure locked if you lock the focus WHILE FOCUS CONFIRMATION IS DISPLAYED.

Now try this: focus, and then take your finger OFF the shutter button, so the green focus confirmation dot light in the finder disappears. Now press the lens button. Focus will be locked to the focus you just set, but the focus confirmation button is no longer locked. Keep holding the lens button, and press the shutter again - you will see that the exposure is now free to change, but the focus is locked.

David

[picman]

Hi again David,

That's it! I've been breaking my head over this and the manual, to me at least, was not clear on this point. But your explanation made it crystal clear! Thank you so much. I think this is pretty handy if you want to focus on something that is not in the middle of your composition and I'll be using it quite a lot I think.

Thanks again and best regards, Bob.