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My 17-40 always shows 40mm in Lightroom...

Started Feb 3, 2014 | Discussions thread
Peter Kwok
Peter Kwok Senior Member • Posts: 2,635
Loose connection

The main board is not getting the zoom position information.  One of the connections of the ribbon cables is probably loose.  It should be an analog signal from a potentiometer wiper.

This may affect AF accuracy also.  Without knowing the focal length setting, the lens would not know how far to move to correct for the phase offset the camera is seeing.

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Peter Kwok
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