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08-29-2009, 01:32 PM   #1
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Am I damaging the new K20?

I've started using an Pentax A50 for trap focus on my K20, does the following apply to an manual lens set to "A" and am I damaging the K20 using it that way?

I pulled this quote from a response by PDL to an earlier Forum thread: Never have the front switch set to AF.s or AF.c and twist the focus ring - on a FA (or AF) lens de-coupled or not. By twisting the focus ring you can/will damage the gears/motor of the AF mechanism.
Brian

08-29-2009, 01:52 PM   #2
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The A50 is not an FA lens. Unless I'm missing something, that warning only applies to FA lenses (or other AF lenses that lack quick shift). And it's not a warning that is really needed - the first time you try it, you realize it doens't work; the camera/lens won't *let* you turn the ring. It's a warning against trying to force it anyhow.
08-29-2009, 07:25 PM   #3
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Brian, I believe the quote you referenced is actually referring to the lens, not the actual camera. The gears within the lens would be damaged if you tried to force them to manually focus while the switch was in Autofocus mode, but as Marc said, it's not like it would be easy to do accidentally. You'd really have to force it to break anything in the lens.
08-29-2009, 08:17 PM   #4
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Brian,

Pentax "A" lens are not autofocus. They are permanently in manual focus mode and are absolutely perfect for trap focus operation.

Garth

08-29-2009, 08:22 PM   #5
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Hm, I rotate my FA 50mm in AF mode just fine. It just spins the gears...can't do it on my 18-250mm though.
08-29-2009, 08:37 PM   #6
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Original Poster
Thanks one and all for the info, but glad I checked just in case,
Brian
08-29-2009, 08:38 PM   #7
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I was using my Vivitar 105 macro and forgot to put the switch to MF, I had no problems at all.
08-29-2009, 08:49 PM   #8
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QuoteOriginally posted by krypticide Quote
Hm, I rotate my FA 50mm in AF mode just fine. It just spins the gears...can't do it on my 18-250mm though.
I think the quote from the manual was speaking precisely to this... With an AF lens that does not have the "Quick Shift" function of the DA line, rotating the focus ring while the AF screw is engaged can damage the gears in the body.

08-30-2009, 01:47 PM   #9
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QuoteOriginally posted by FHPhotographer Quote
I've started using an Pentax A50 for trap focus on my K20, does the following apply to an manual lens set to "A" and am I damaging the K20 using it that way?

I pulled this quote from a response by PDL to an earlier Forum thread: Never have the front switch set to AF.s or AF.c and twist the focus ring - on a FA (or AF) lens de-coupled or not. By twisting the focus ring you can/will damage the gears/motor of the AF mechanism.
Brian
Yup, I said that.

On a non-Pentax and Pentax Auto Focus lenses without Quick shift (not the DA series of lenses), if you use the focus ring to finess focus, you can end up damaging the gears in either the lens or the body. The focus motor is not designed to be rotated by the gear linkage in the lens. All you have to do is chip one tooth off of the series of gears to cause issues.

However, If you are using a manual lens - focusing the lens does not effect the AF motor. The prefered setup is to set the camera body to MF on the front switch. By my experience on the *istDs, K10D and K20D, when the switch is set to MF the AF screw on the lens mount is retracted. Therefore with a AF lens (using only screw based AF) the AF motor function is disabled. The AF circuits are still usable.

In my case - when I use my FA 50mm, my Tokina AF 28-70mm macro or my Vivitar 300mm manual lens (the only pure manual lens I have) and I want to manually focus with these three lenses. I set the switch to MF (retracting the AF screw) - when I want to use the AF circuits to check focus I press the OK/AF button and use the green hexagon to see if I am in the ball park. (Note: I have de-coupled AF from the shutter button so I can not speak to whether this works with shutter button activated AF or not)

With manual lenses - there is no connection between the camera and the lens used in focusing. Therefore there will not be any damage to the gearing/motor in the camera. Although I would still suggest that when using manual focus lenses that you set the focus switch on the front of the camera to MF, if for nothing else but to retract the screw on the lans mount.

The Elitist - formerly known as PDL
08-30-2009, 02:00 PM   #10
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This is odd. That can happen accidently very easily. It is a rule of thumb if not even more strict, like a demand to incorporate a free wheeling diode in any circuit using a motor, so when the motor keeps rotating by inertia, or is being externaly rotated someway the diode does not allow the motor to work as a generator and feed voltage back to the circuit damaging it.

I'd expect something similar to be used by defauly in any mechanical systems. It is a part where almost certainly your arm will be and even more, it is a part designed to be turned.
If its not completely locked, it would be logical that it should safely endure turning.

None the less, manual says that it is not the case.
08-30-2009, 05:44 PM   #11
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QuoteOriginally posted by ytterbium Quote
This is odd. That can happen accidently very easily. It is a rule of thumb if not even more strict, like a demand to incorporate a free wheeling diode in any circuit using a motor, so when the motor keeps rotating by inertia, or is being externaly rotated someway the diode does not allow the motor to work as a generator and feed voltage back to the circuit damaging it.

I'd expect something similar to be used by defauly in any mechanical systems.
Well, that's what Quick Shift is. Pentax is somewhat unusual in making this a more or less standard feature.
08-30-2009, 05:54 PM   #12
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QuoteOriginally posted by PDL Quote
Yup, I said that.

On a non-Pentax and Pentax Auto Focus lenses without Quick shift (not the DA series of lenses), if you use the focus ring to finess focus, you can end up damaging the gears in either the lens or the body. The focus motor is not designed to be rotated by the gear linkage in the lens. All you have to do is chip one tooth off of the series of gears to cause issues.

However, If you are using a manual lens - focusing the lens does not effect the AF motor. The prefered setup is to set the camera body to MF on the front switch. By my experience on the *istDs, K10D and K20D, when the switch is set to MF the AF screw on the lens mount is retracted. Therefore with a AF lens (using only screw based AF) the AF motor function is disabled. The AF circuits are still usable.

In my case - when I use my FA 50mm, my Tokina AF 28-70mm macro or my Vivitar 300mm manual lens (the only pure manual lens I have) and I want to manually focus with these three lenses. I set the switch to MF (retracting the AF screw) - when I want to use the AF circuits to check focus I press the OK/AF button and use the green hexagon to see if I am in the ball park. (Note: I have de-coupled AF from the shutter button so I can not speak to whether this works with shutter button activated AF or not) .....It does work also if you have the shutter button 1/2 pushed for AF setup also..That's what I use.

With manual lenses - there is no connection between the camera and the lens used in focusing. Therefore there will not be any damage to the gearing/motor in the camera. Although I would still suggest that when using manual focus lenses that you set the focus switch on the front of the camera to MF, if for nothing else but to retract the screw on the lans mount.

The Elitist - formerly known as PDL
I have the same "A" 50/2, and the focus trap works fine. Body on MF, Lens on "A", and use your E-Wheels to change the SS or f/stop. If fact here is an image I took tonight of my son with a K20d & A-50/2
I focused on his right eye at f/10 or f/13 with the on-board flash.

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