?Damage caused by over-turning focus ring?
Lens in question, Canon 50mm F1.4 microUSM.
The lens belongs to a friend of mine. He told me that it was being tried out by a friend of his and he observed this person turn the focus ring (in MF) beyond the calibration markings, and he continued to turn it until the slight resistance registered with him. Perhaps 60deg too far, but without using force. The friend was expecting the ring to reach a stop position and only gradually reacted to the slight change in feel in the focus ring as it was turned beyond the calibration markings.
My friend now thinks the lens is front focusing. He ran the lens through tests after he bought it about 6mo ago. Now, after he became suspicious that the over-turning of the focus ring had damaged the focusing performance of the lens, he has repeated those tests.
I told him I would seek some advice here about whether it is likely that over-turning the focus ring would damage the lens.
It's a bit shocking if damage can be caused in this way. There is no warning about this in the documentation with the lens, and the overturning was basically accidental and not abusive.
Any reactions gratefully received. :thumb
Thanks.
Neil
The lens belongs to a friend of mine. He told me that it was being tried out by a friend of his and he observed this person turn the focus ring (in MF) beyond the calibration markings, and he continued to turn it until the slight resistance registered with him. Perhaps 60deg too far, but without using force. The friend was expecting the ring to reach a stop position and only gradually reacted to the slight change in feel in the focus ring as it was turned beyond the calibration markings.
My friend now thinks the lens is front focusing. He ran the lens through tests after he bought it about 6mo ago. Now, after he became suspicious that the over-turning of the focus ring had damaged the focusing performance of the lens, he has repeated those tests.
I told him I would seek some advice here about whether it is likely that over-turning the focus ring would damage the lens.
It's a bit shocking if damage can be caused in this way. There is no warning about this in the documentation with the lens, and the overturning was basically accidental and not abusive.
Any reactions gratefully received. :thumb
Thanks.
Neil
"Snow. Ice. Slow!" "Half-winter. Half-moon. Half-asleep!"
http://www.behance.net/brosepix
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0
Comments
Tha Canon 50mm, f1.4 has a micromotor-USM. The manual focus is connected via a clutch mechanism. The manual focus cannot be forced beyond the stops in a normal lens. There are no "hard" stopping points to be felt. If the lens is rotating beyond the normal focus stops, as indicated by the focus scale, it is damaged or defective and needs repair.
More than likely your friend misunderstands how the clutch works, or that the lens has a clutch in the first place. More than likely there is nothing wrong with the lens.
Some of the focus tests, those using a "scale" or "ruler" can confuse the autofocus of the camera and I no longer believe in, or use or recommend, those tests.
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Very valuable input.
Many thanks, Ziggy.
I'll pass this on to my friend.
Neil
http://www.behance.net/brosepix