Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-22-2010, 09:15 AM   #1
Veteran Member




Join Date: Oct 2010
Location: Baltimore
Posts: 2,542
Pentax-F 70-210mm

I was cleaning this zoom, tried it out inside my studio, worked fine, sharp images. I take the lens outside, and now it can't seem to focus to infinity... any ideas?

I did notice battery is low and I'm hoping this is it. (I don't have charged batteries here) but my 30-70 is working fine on the camera and this too I cleaned this morning...



11-22-2010, 12:47 PM   #2
Veteran Member




Join Date: Oct 2010
Location: Baltimore
Posts: 2,542
Original Poster
Fixed it!!!

Apparently, while cleaning the lens, the focusing mechanism, which holds the first lens in place moved just slightly enough to throw off the infinite end. There are 3 sets screws which were so loose that the lens rotated slightly while cleaning. I went ahead and did some manual "calibration" of the focusing mechanism while mounted on camera and getting an in focus indication, re-tightened set screws and works like new...
11-22-2010, 12:57 PM   #3
Senior Member




Join Date: Sep 2007
Location: Seattle
Posts: 245
Nice Job!
11-22-2010, 01:05 PM   #4
Veteran Member




Join Date: Nov 2010
Location: Huntsville, Alabama
Posts: 422
When I was working on the same lens last week, I ended up getting the front element way off.

The autofocus works fine and it can infinity focus..... but it goes way past infinity focus - infinity focus is at about 25 feet on the distance scale.

It can also focus at about 2 feet when set to 210mm.

11-23-2010, 09:34 AM   #5
Veteran Member




Join Date: Oct 2010
Location: Baltimore
Posts: 2,542
Original Poster
QuoteOriginally posted by cyclone3d Quote
When I was working on the same lens last week, I ended up getting the front element way off.

The autofocus works fine and it can infinity focus..... but it goes way past infinity focus - infinity focus is at about 25 feet on the distance scale.

It can also focus at about 2 feet when set to 210mm.
Wow!!! I've got the SMC-F 70-210 f4-5.6 and it shows Infinity as beyond @ 60ft on the distance scale...
11-23-2010, 11:32 PM   #6
Veteran Member




Join Date: Nov 2010
Location: Huntsville, Alabama
Posts: 422
QuoteOriginally posted by theunartist Quote
Wow!!! I've got the SMC-F 70-210 f4-5.6 and it shows Infinity as beyond @ 60ft on the distance scale...
Yeah.. I might leave it how it is since it really doesn't affect focusing and it allows me to focus closer than normal.

It is basically adjusted for the closest focus possible. If I set it any closer, it binds at close focus.
11-24-2010, 02:52 AM   #7
New Member




Join Date: Mar 2010
Posts: 11
I've taken my smc-f 70-210 apart from the front to clean fungus off the rear of the front element and now its back together I can't get it to focus at infinity either. Which 3 set screws did you adjust the unartist ? the three on the main lens barrel under the distance window strip (2) and rubber (1)
Thanks
11-25-2010, 05:36 AM   #8
Veteran Member




Join Date: Oct 2010
Location: Baltimore
Posts: 2,542
Original Poster
QuoteOriginally posted by timestwo Quote
the three on the main lens barrel under the distance window strip (2) and rubber (1)
Thanks
No, these are not the ones. The 3 set screws are located near the end of the telephoto barrel (slot screw). They can just be loosened and the focusing ring can turn independent of the lens...

11-30-2010, 02:13 AM   #9
New Member




Join Date: Mar 2010
Posts: 11
thanks -- obvious once you know how!
Cheers
01-13-2011, 11:18 AM   #10
Veteran Member




Join Date: Oct 2010
Location: Baltimore
Posts: 2,542
Original Poster
QuoteOriginally posted by timestwo Quote
I've taken my smc-f 70-210 apart from the front to clean fungus off the rear of the front element and now its back together I can't get it to focus at infinity either. Which 3 set screws did you adjust the unartist ? the three on the main lens barrel under the distance window strip (2) and rubber (1)
Thanks
I just looked at my 70-210 and dang, it's got fungus, it still take sweet images but I want to see if I can get it apart to clean!!! Looks like it's just inside the top element. Id like to try to save this lens, how did you get the front apart? I can see 3 Philips type screws right around the focusing ring... Can you give a little hint as to where you went from here, any special tools, heating, etc.


Thanks, Rick
01-16-2011, 05:55 PM   #11
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,814
In front, there are three elements together. Look here:



Two are cemented together. They are all in a threaded carrier that screws in and out using the filter threads. If you look at the lens head-on, you'll see 4 slots for a lens spanner tool. The outer slots are in a lock ring that keeps the carrier in one place. If you can unscrew the lock ring, you can screw the carrier in and out. That's also the infinity focus adjustment. The inner slots are in a ring that keeps the group together.

The ring might be locked in place with lacquer or paint. The slots aren't all that far away from the front element, so if you improvise a tool here, make sure it's a good one. If it slips, bad things may happen. I use needlenose pliers with slightly ground tips so they just fit the slots. If it doesn't move on my first try, I drip some acetone in the filter threads and try again.

Because there are three lenses in that group, your fungus could be inside the group. I hope not; it's even worse to get that inner ring off. Another possibility is it's not fungus. It could be glue breaking down between the glued elements. In that case, a repair is possible but not worth the trouble.

When you put everything back together, check infinity focus at the 70mm end and 210mm. I can't recall if they're different, but it's a good idea to check in case. Then tighten the ring. I did mine a few years ago and it hasn't moved.

More repair information on the lens:

Pentax 70-210 Repair
01-19-2011, 04:57 AM - 1 Like   #12
Veteran Member




Join Date: Oct 2010
Location: Baltimore
Posts: 2,542
Original Poster
Thanks and great link!!!

So far no image degrading, still colorful, sharp and contrasty. Plus, tested on white background and you cannot see anything. A guy at the camera store said that it'll be OK just as long as it's on the front element v. the back...

I took a look at the link, and it's a little intimidating. I am currently working on a 135 prime that had stuck aperture, got it apart, cleaned aperture blades, now snappy but struggling to piece back together... :-)

Rick
03-28-2011, 08:40 AM   #13
Veteran Member
paperbag846's Avatar

Join Date: Jul 2010
Photos: Gallery
Posts: 2,396
Ever since I bought this lens, I knew there was something funny about infinity focus. I only saw at the long end, though.

After reading this and scrounging up a screwdriver, I'm happy to say my lens is cured! I think I lost a little off the close focus side because I can't be bothered to do this perfectly, but I am very happy. Thank you all!
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!
k-mount, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wanted - Acquired: [langtitle=de]Tamron sp 3.5 70-210mm 19AH or Vivitar series 1 70-210mm ve[ kingstyle79 Sold Items 1 07-26-2010 12:10 PM
For Sale - Sold: Pentax SMC-A 70-210mm f4 Macro zoom; Pentax A3000 film SLR; Vivitar 28-210mm z NeverSatisfied Sold Items 9 05-14-2010 01:37 PM
Pentax A 70-210mm vs Vivitar S1 70-210mm Zeeke Pentax SLR Lens Discussion 11 04-24-2010 07:57 AM
Compare the lens coating of Takumar-F 70-210mm and smc Pentax-F 70-210mm jcdog2006 Pentax SLR Lens Discussion 13 02-19-2010 08:16 AM
Tamron adaptall-2 zoom comparison: 70-210mm 19AH vs 80-210mm 103A virgilr Pentax SLR Lens Discussion 8 09-17-2009 07:29 PM



All times are GMT -7. The time now is 03:37 AM. | See also: NikonForums.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