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

Started Feb 3, 2014 | Discussions
zalle Contributing Member • Posts: 898
My 17-40 always shows 40mm in Lightroom...

I opened my 17-40 because it had a loose screw and the zoom was stiff.

Fixed it, put it back together and it wors, the zoom is still somewhat stiff, but it's not too bad.

The one problem I'm having now is that when I import an image to Lightroom, all apictures at all focus distances show 40mm. Some contact is not working well. What can it be?

I used this guide: http://notabs.org/canon/ef17-40/disassembly.html

Thanks for any help

OP zalle Contributing Member • Posts: 898
Flash only recognizes 40mm as well... NT

No text.

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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OP zalle Contributing Member • Posts: 898
Re: Loose connection - Yes

Hi,

Thanks.

Just opened it again and put it back together carefully, and now it's OK!

Mimik
Mimik Regular Member • Posts: 152
Re: My 17-40 always shows 40mm in Lightroom...

Could be the zoom brush. I damaged mine on my 24-70, after that it only showed 70mm in LR and the focus was very slow and inaccurate. After I got a new zoom brush all was fine again.

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