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12-17-2014, 06:10 AM   #1
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50-135mm F/2.8 issue

Hi all,

I have just recently have a second hand Pentax DA 50-135mm ED IF SDM on ebay, checking up and problem came out as following
- Camera ask for "Input Focal Length" when I start the camera (I'm using K30)
- I can still modify aperture but strange thing is it could be maximum to F/2.0 while the lens said only F/2.8
- Auto focus does not working

Any suggestion, I'd appreciate it

12-17-2014, 06:26 AM   #2
JinDesu's Avatar

Join Date: Jun 2011
Location: New York City
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Something is wrong with the communication between lens and camera. Either the pins are not clean and you should try that first, or the lens internal chip is damaged (by water or whatever). The only time I've encountered something like this before was when my lens got some water in it. It solved itself after drying out, but I don't know what happened to yours.

So clean the contacts on the back of the lens and on your camera first.
12-17-2014, 06:28 AM   #3
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Sounds like you might need to clean the contacts. Those are the little brass colored bumps plus the two brass strips on the back of the lens. Be gentle with them. Google how to do it if you don't know how.
12-17-2014, 07:18 AM   #4
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Hopefully you can get the problem resolved, because the 50-135 is a great lens!

12-17-2014, 08:25 AM   #5
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Also, depending on how it was advertised (excellent, etc.); I would consider sending it back for a refund.
12-17-2014, 08:29 PM   #6
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Original Poster
Thank for your suggestions.
Yesterday I did a quick clean in the lens contact but nothing change. I'll try one more time.
12-21-2014, 01:35 PM   #7
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Today I've follow a topic to fix SDM DIY. Fortunately, I have a chance to see the autofocus working again.
The situation is if the lens is completely assembled with all parts, autofocus does not work but other information and functions are fine
If I remove a part with 2 golden connect point, pls have a look at picture
Autofocus works but on camera screen, it's blinking between AF mode and MF mode

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