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03-09-2017, 08:50 AM   #1
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FA*85 1.4 Auto Focus Sound on K-1: Is this normal?

Just got my FA*85 1.4 for my K-1, but it I don't know if the AF sound is normal or not. It makes a shuddering sound when focusing...




Last edited by dcpropilot; 03-09-2017 at 09:19 AM.
03-09-2017, 09:42 AM   #2
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Thanks! The speed and accuracy seems good. My main concern is that there's a pulsing, shuddering, more evident during long focus throws. Sort of like something's dragging or the clutch is hanging up? Or maybe this is normal...?
03-09-2017, 10:40 AM   #3
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Congratulation! You now have one of the most awesome lens Pentax ever made.

Your lens sounds normal to me.
03-09-2017, 10:50 AM   #4
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Sounds bad...

QuoteOriginally posted by fwbigd Quote
Congratulation! You now have one of the most awesome lens Pentax ever made.

Your lens sounds normal to me.
having owned this lens for 20+ years, and having used it on two Pentax film cameras (PZ-1 and MZ-5) and two digital cameras (*ist D and K5), it sure does NOT sound normal. It sounds like something either needs lubricating, or the connectors are not quite meshing and are slipping. I'd get it checked - your camera may be faulty.

Cheers,
Cameron

03-09-2017, 10:53 AM   #5
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Ask @dcshooter for his input. A CLA is cheap insurance if continued operation.
03-09-2017, 10:54 AM   #6
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My experience with Screwdrive lenses on K-1 is the typical Pentax focusing protocol - Zip-chu-chu - as the algorithm gets close, then fine tunes lock. For a long time we argued Pentax AF is slower than CN but more accurate. The chu-chu is the 'more accurate' part.

Whether that is what you are hearing I don't know, but it sounds like the screwdrive isn't meshed well with the lens.
03-09-2017, 10:55 AM   #7
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The camera is ok. It only happens with this lens. I wonder who in the U.S. would be able to service it?

---------- Post added 03-09-2017 at 12:56 PM ----------

QuoteOriginally posted by UncleVanya Quote
Ask @dcshooter for his input. A CLA is cheap insurance if continued operation.
Thanks!
03-09-2017, 11:00 AM   #8
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Eric Henderson is another option but I tend to use Brian (dcshooter).

03-09-2017, 11:04 AM   #9
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Here's another video. I put the camera and phone on a table to amplify the sound.
03-09-2017, 11:37 AM   #10
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It is not the normal sound. Are you sure the focus ring is enable in af position.?
Try to change from af to manual focus on the lens some times. You Must not opérate the lens in manual mode if the camera is not in manual focus mode. It has not quick shift.
Can anybody explain it in better english?
03-09-2017, 11:40 AM   #11
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QuoteOriginally posted by pasorro Quote
It is not the normal sound. Are you sure the focus ring is enable in af position.?
Try to change from af to manual focus on the lens some times. You Must not opérate the lens in manual mode if the camera is not in manual focus mode. It has not quick shift.
Can anybody explain it in better english?
On the FA* lenses with the AF/MF clutch if you push the focus ring one way it is AF and the ring is locked. If you push the other way it will work as MF even if the camera is set to AF and this is OK. It will not AF in this mode. As indicated above there is no QuickShift. If the ring is not fully pushed either way I'm not sure what would happen but in my only FA* lenses (80-200 f/2.8 and 300 f/4.5) the lens has not been able to get into this inbetween setting - it has clicked fully into one or the other without any play to permit hanging in this theoretical middle state.

---------- Post added 03-09-17 at 01:43 PM ----------

I just verified this on my FA* 300. If I push it back towards the body the lens clicks into manual focus mode. Clicking it forward puts it back to AF. Please note that I then needed to turn it slightly before it locked in place in the AF mode. Also note that right above the window to the lens distances it is labeled Auto Focus to show when it is in that mode.

---------- Post added 03-09-17 at 01:46 PM ----------

From your videos it isn't clear that the "auto focus" words appear clearly - are they partially covered? See this picture for how they should appear:

https://www.pentaxforums.com/lensreviews/showfull.php?product=190&bigimage=s...85mm_F1_4_.jpg

---------- Post added 03-09-17 at 01:57 PM ----------

Just put the FA* 300 on my camera. If I confuse it I can get some of the behavior like this while it hunts. Put something in the front of the lens at a distance that it can focus on and try again. If it quickly locks in and doesn't hunt it may be OK - the hunting itself sounds nutty when happening - mine has been CLA'd and is very agile when focusing normally. It was hard to find something with poor contrast to get it to fail. I am still not postive that your lens sounds right - it does seem a little odd.

Last edited by UncleVanya; 03-09-2017 at 11:48 AM.
03-09-2017, 12:04 PM   #12
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Here's what I'm doing
03-09-2017, 01:11 PM   #13
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my FA* 85 f1.4 behaves absolutely the same as in your video. I noticed this sound maybe half year ago. If you turn your camera down, you will hear that screw drive motor works with more effort and slower to focus from minimum focus distance to infinity.
Maybe someone can post how this lens should sound if it is "normal"?
Here is video from youtube (not my lens)
03-09-2017, 01:53 PM   #14
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I think that I already found the reason. The first gear that is on the screw drive shaft is cracked.
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03-09-2017, 02:10 PM   #15
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QuoteOriginally posted by Medex Quote
I think that I already found the reason. The first gear that is on the screw drive shaft is cracked.
What is that made of?
It appears metal?
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