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Manual Focusing on AF mode
Topic Started: Mar 28 2009, 08:17 PM (382 Views)
jkkm
Alpha Newbie
Hi all,

I accidentally rotate the focusing on my 100mm/f2.8 lens and the camera is in AF mode, will I cause any damages to the lens?

Thanks
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Ming
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90609866
Try not to do that in the future then ... :sweat:

Anyway , you can easily check whether your Lens can still be AF in AF Mode or not ma ? If its still working & focusing properly , that means no harm at all .

And ... I think you posted at wrong section ...
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Birder
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It is possible ..... ONLY if you are using A700 or A900.

In the menu, change AF-A setup from "AF-A" to "DMF".
Then at the front of your camera, ensure the the focus switch (in front near lens mount) is switched to "A"

After the camera AFs, you can manually do turn the focus ring.... Works with any lens..


edit/add:

Second method is buying SSM lens with DMF switch..

If you do not have the 2 options above... Do not forcibly turn your focus ring.. or you will either will damage your lens or your camera's AF system

Edited by Birder, Mar 28 2009, 08:52 PM.
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jkkm
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thanks so much.

I am still using A100.:)
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Birder
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jkkm
Mar 28 2009, 09:06 PM
thanks so much.

I am still using A100.:)
Then the only way you can do it is to switch to Manual Focus mode by changing the focus switch at camera front to "M"
You are then fully manual..

hehe... Unless you got 135mm STF lens. That lens is fully manual :)
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Mino
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Best method on SSM lens:

There is STD or Full Time mode on the SSM lens under DMF switch.
Use full Time so that you can MF to take control at anytime in progress of AF. Just turn the manual focus ring.


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Ming
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... 100mm f2.8 ... A Macro Lens or the Soft Focus ?

If i remembered correctly , its not easy to turn the focusing ring of the Lens if the AF/MF button on the camera is set at AF . Same goes to A100 , if the Camera is set at AF Mode , the Lens focusing ring is quite hard to turn ma ... Or did you purposely turn it by force ?

How now ? Anything faulty with your Lens now ?
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weishengg
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i am no expert in this area of electrical and electronics, but with my limited knowledge, i don't think it would cause any harm to your camera if the sony engineers haven't been sleeping.

when you rotate the MF ring while in AF mode, you are essentially forcing the autofocusing screw to twist. the screw is couple to a micro-dc-motor in the body of the camera, so you are basically forcing the motor to turn.

nothing wrong with turning the motor in either direction against its will, its built to rotate in either direction anyway. however, that could generate some back emf voltage in the opposite polarity of how it normally works. if the (eddy) current is allowed to flow in the opposite direction, this could screw up the circuit and some of the electricals that are connected with the motor.

but any sensible electrical engineer working on this system would definitely put in a diode which is essentially a very high resistance ONE-way resistor. this prevents the eddy currents from flowing and damaging your electricals.

however, some screw-ups could still happen for the following reasons:
1. you twist the MF ring with so much torque that you generate a high enough eddy current to fry your circuit
2. you rotate the MF ring WHILE the camera is auto-focusing (i.e. the dc-motor is active). this could cause a current surge to the dc-motor. this could fry some other electricals. but again, its unlikely it'll happen, they should have a proper motor controller or a surge protector.
3. sony cuts costs and hires some goondoo people like me as their engineers.


so in essence, you're safe! but still not adviceable la :p
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Trigger Happy
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some twisting will occur at some point in time, just try not to do it.
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