Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-21-2011, 11:44 PM - 1 Like   #16
Site Supporter
mikeSF's Avatar

Join Date: Jan 2009
Location: East Bay Area, CA
Photos: Gallery
Posts: 5,705
i spoke to someone at CRIS who said 1) they've NEVER heard of anything like this, and 2) i'd have to pay the repair cost since i am the second owner of this nearly new lens.

folks, check your lenses - same could happen to YOU!

07-23-2011, 09:10 AM   #17
Junior Member




Join Date: Jun 2011
Location: Gulf Coast
Posts: 45
Original Poster
FA31mm focus assembly

I received my FA31mm from C.R.I.S. camera repair and all seems in order. In my cover letter with the lens sent for repair I mentioned what was reported here from other members as regards the screws. So lets hope they used the thread tight so it does not happen again.
07-23-2011, 09:51 PM   #18
Site Supporter
mikeSF's Avatar

Join Date: Jan 2009
Location: East Bay Area, CA
Photos: Gallery
Posts: 5,705
good to hear Billy. and yes, i hope they threadlocked the screws properly.

here is my 77 after the screws fell off:

07-24-2011, 05:52 AM   #19
Junior Member




Join Date: Jun 2011
Location: Gulf Coast
Posts: 45
Original Poster
Crikey! needless to say this should not happen on any lens let alone a limited series.
It must be a QC issue meaning there is no QC management to oversee the assembly.

I used and still use Pentax 67s and thought I would go with the K5 and limiteds after using both Olympus E1 and E3 and Sony a900 (a heavy beast that got me thinking light). Never had any issues, in fact have never had any issues with the 67s for the last 30years! I earn my living with photography and am a bit concerned that I may have seduced myself into Pentax romance! I still have hope. I think Ricoh may treat Pentax as the jewel in their crown.

08-10-2011, 03:41 PM   #20
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 9,193
QuoteOriginally posted by wlachan Quote
The solution is to soak the screw thread with threadlock beforehand then it will form a secure bond once cured (~1 wk) because the threadlock being used by Pentax is Threebond 1401 which is a low strength threadlock (works great when used properly).
Thanks for sharing!
I just "liked" your post.

I hope I'll never have to fix my FA 77/1.8. I'll watch for a lose focus ring.

I'm with you regarding QC. If Ricoh could improve QC and maybe iron out some systematic problems (16-50 & 50-135 SDM) so that people can buy expensive Pentax equipment with more confidence that may make quite a difference in the long run.

Currently, I would only pay MF prices for a 16-50 or 50-135 zoom. There seem to be users that have no trouble but the frequency of which one hears about SDM problems even after repairs (typically out of warranty then) is just too high (for my taste).
08-11-2011, 06:34 AM - 1 Like   #21
Junior Member




Join Date: Jun 2011
Location: Gulf Coast
Posts: 45
Original Poster
Well I did receive my lens and all seems in good order. I considered that the Pentax K5 and certain lenses would be of pro quality and of lasting endurance as my 67s. It's all there but something maybe adrift I fear. Although I have the FA31mm and the FA43mm I was considering the 16-50 but have reservations at this point because of the 'hit or miss' SDM situation. Managing quite well though as the two lenses I have are similar to the 67s 90mm and 135mm which are my workhorse lenses.
All the best
08-26-2011, 05:20 PM   #22
Senior Member




Join Date: Mar 2011
Location: United States
Posts: 183
Did the image quality improve with the loose barrel repaired?
08-26-2011, 05:35 PM   #23
Senior Member




Join Date: Mar 2011
Location: United States
Posts: 183
I saw some other threads with reports of optical alignment issues for the 31. What could be the cause of that? Are they just sitting in the barrel at a slight angle? Are the optical groups in some lenses bad? There a user in this thread (post #7) who says he had an optical group replaced.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/100275-where-fa-31mm-lenses.html

Can you elaborate more on the construction of this lens? Can the alignment of the optics be adjusted DIY too or just the focus barrel? Are there screws to adjust the groups?

Would a loose barrel be the primary cause for optical alignment issues?




QuoteOriginally posted by wlachan Quote
I have no idea how much it will cost but probably a standard fee like $120? However, something like this should never happen and you might get lucky with CS. If the dropped front section and the focus ring aren't damaged, you can just put them back together and it will be good as new.

1) Unscrew the front metal retaining ring (on the filter ring) with a piece of rubber (the ring is not tight but getting a good grip can be tricky). You can also get the proper rubber tool on eBay for a few bucks only.
2) Remove 3 small screws that holds the filter ring.
3) Remove the hood.
4) Assemble the focus ring.
5) Assemble the front section and make sure the front lens group is not loose (screw tight by hand will do).
6) You should be able to see the screw marks on the focus ring, just line them up and put back the screws.
7) Check infinity.
8) Threadlock the screws.
9) Assemble the hood and everything else (remember threadlock all screws with low strength threadlock and let them cure for a week at least b4 use).

PS: These are off my head so if the fragile contact brush was damaged, then you will have to send it in.



Last edited by pz1fan; 08-26-2011 at 05:45 PM. Reason: minor edit
08-26-2011, 06:27 PM - 1 Like   #24
Veteran Member
wlachan's Avatar

Join Date: Sep 2006
Location: Canada
Photos: Albums
Posts: 2,626
The FA31 is quite different from other Limited lenses structurally. The 2nd and 3rd lens groups are basically concealed in metal barrels sliding against each other (w/o grease) and held by 3 plastic rollers each. The optical alignment is maintained by the "tightness" of these metal barrels. All inner metal barrels should slide smoothly yet w/o any wobble at all, not even a tiny bit (possible but expensive to manufacture). However, from what I have observed from 5-6 samples over the years (MIJ & AIV alike), only 2 was firm, and the rest wobble by varies degree. This does indeed have significant impact on optical alignment and sharpness, especially toward wide open. The difference is visible too when stopped down but may not be obvious to all users. Those with loose barrels can be well compensated by shifting the 1st lens group around which is held by 3 screws. However, the degree of compensation is very limited (and I don't even know if it was done this way in the factory). Also, since the barrels are loose, lens optimised for landscape orientation will suffer in portrait orientation and I did some tests to confirm this. Whether the degree of misalignment in portrait orientation is inline with most consumer AF lenses, I don't know. For ultimate alignment, MF lenses with fine helicoil threads like the good old K/M lenses are king, or the moderm Zeiss ZK/ZM/ZE lenses etc.

My recommendation of choosing a good FA31 before putting it to optical test, is to hold the lower section of the lens firmly and shake it a little. If the hood wobble, it's a goner. If the hood is firm, then hold the whole lens and shake it again. If you hear something wobbles inside, it's the 3rd(rear) lens group. Not a good sign either. But the ultimate test would be wide open sharpness, and it must be done on tripod with flat target like a wall at around 1 meter or farther (1 landscape & 2 portrait orientations with bubble level). Aligning the lens to the target perfectly will be tricky, and slight focus error can lead to misleading interpretation. The interesting thing is that my same FA31 was quite good when I was shooting film, but had blurry LHS on the K-m. Perhaps film was more forgiving due to its thickness as I have discovered even 0.1mm shift can make quite an impact on digital sharpness (what happens to DA14 field curvature as well).

As on replacing the lens group by Pentax Japan, I would imagine the whole tube (either the 2rd or 3rd) was replaced instead of an individual glass(es). My own conclusion is that the inner barrels w/o glass can be the source of problem too, but you never know until open up.
08-26-2011, 07:50 PM   #25
Site Supporter
mikeSF's Avatar

Join Date: Jan 2009
Location: East Bay Area, CA
Photos: Gallery
Posts: 5,705
QuoteOriginally posted by billy moon Quote
Well I did receive my lens and all seems in good order. I considered that the Pentax K5 and certain lenses would be of pro quality and of lasting endurance as my 67s. It's all there but something maybe adrift I fear. Although I have the FA31mm and the FA43mm I was considering the 16-50 but have reservations at this point because of the 'hit or miss' SDM situation. Managing quite well though as the two lenses I have are similar to the 67s 90mm and 135mm which are my workhorse lenses.
All the best
well mine came back after a month and now has some new marks on the front element. nice job, cris.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
fa31mm, focus, issue, k-mount, pentax, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
FA 31mm limited focus ring is loose? kuau Pentax SLR Lens Discussion 16 06-28-2011 05:45 PM
Loose focus/zoom ring. Should I return it? cerebrate Pentax SLR Lens Discussion 11 03-22-2011 04:20 PM
DA L 18-55mm manual focus ring too loose jamesv93 Pentax SLR Lens Discussion 2 11-28-2009 12:03 AM
How much focus would I loose mounting a m39 on my pentax? melander Pentax SLR Lens Discussion 5 02-09-2009 05:57 PM
Focus collar on DFA 100mm f2.8 macro cygnet Pentax SLR Lens Discussion 4 10-07-2008 07:02 AM



All times are GMT -7. The time now is 07:43 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top