Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-08-2009, 11:05 PM   #1
Veteran Member
yyyzzz's Avatar

Join Date: Mar 2009
Location: Salt Lake City, UT
Photos: Gallery
Posts: 509
Help on sticky apertures

My Pentax 28mm f2.8 has sticky apertures. There must be some discussions about how to open the lens from the front.

I have been able to open the lens from the mount. But I could not get access to the mechanism. Thanks.

07-08-2009, 11:18 PM   #2
pbo
Veteran Member
pbo's Avatar

Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 891
I dunno about Pentax 28/2.8, but on my Sigma 16/1.8 fisheye, the whole rear group is screwed on (without screws, the whole group is screwed in), and beneath it is the aperture mechanism.
Just in case it's your first time doing this, be careful not to make mistakes like I did - that is, be careful not to lose a ball bearing that makes aperture click (of course, if you do, you can say you modified the lens so that it's now stepless ), and clean aperture without actually opening the aperture mechanism - I did, and spent maybe two days putting it back. Great experience, though, feel like I can open a repair shop now

Bo.
07-09-2009, 12:25 AM   #3
Senior Member
wavecurrent's Avatar

Join Date: Jul 2007
Location: Kiruna, Sweden
Posts: 147
Well, I have successfully repaired a couple of the Pentax K and M lenses with a sticky apeture(K28/3.5, K35/3.5 & M35/2.8), don't know if you have seen the follwing tread about lens repair? Anyway here it is.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/44776-disassem...-needed-2.html

But you should be able to access is from the mount side of the lens, check my images on my flickr site.

Mike
07-09-2009, 12:52 AM   #4
Veteran Member
yyyzzz's Avatar

Join Date: Mar 2009
Location: Salt Lake City, UT
Photos: Gallery
Posts: 509
Original Poster
Thanks for the quick note.

I had no problem in opening the lens mount and put it back. It took me about 45mins for the first time. See attached photos.

My problem is that I could not open the front. I could open my 50mm without much difficulty. But I could not loosen the cover which has the sign Pentax SMC....

Attached Images
View Picture EXIF
PENTAX K10D  Photo 
View Picture EXIF
PENTAX K10D  Photo 
View Picture EXIF
PENTAX K10D  Photo 
View Picture EXIF
PENTAX K10D  Photo 
View Picture EXIF
PENTAX K10D  Photo 
07-09-2009, 01:08 AM   #5
Veteran Member
yyyzzz's Avatar

Join Date: Mar 2009
Location: Salt Lake City, UT
Photos: Gallery
Posts: 509
Original Poster
Found a way

Use double side sticky tape. The next step is to find the mechanism and learn to clean a front element. Any suggestions? Thanks.

Last edited by yyyzzz; 07-09-2009 at 01:26 AM.
07-09-2009, 04:51 AM   #6
Senior Member
wavecurrent's Avatar

Join Date: Jul 2007
Location: Kiruna, Sweden
Posts: 147
Is it possible to unscrew the front and rear lens assembly, I did that on the M35/2.8. I never had to deal with individual lenses. Then it was relative "easy" to access/ disassemble the aperture and cleaning completely of any grease. Is the front element dirty on the inside?

Mike
07-09-2009, 05:31 AM   #7
Veteran Member
yyyzzz's Avatar

Join Date: Mar 2009
Location: Salt Lake City, UT
Photos: Gallery
Posts: 509
Original Poster
I do not know; look at the small dots

Please see attached photos. I am not sure what kind of problem it is. They are inside the front element. Any insights?
Attached Images
View Picture EXIF
PENTAX K10D  Photo 
View Picture EXIF
PENTAX K10D  Photo 
View Picture EXIF
PENTAX K10D  Photo 
07-09-2009, 08:33 AM   #8
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,838
I like to check the optical diagram first to see how many lens elements there are. It's not always easy to tell which surface is affected.



I know all of the lenses in front of the aperture blades can be removed as one assembly. There are pairs of rectangular slots, 180 apart, easy to see in your second photo above. They are for a tool called a lens spanner that fits the slots and unscrews the rings. I improvise with needlenose pliers or dividers with tips ground to fit the slots. One outer ring removes the group from the lens, and each element can be removed from that group with a similar ring or some other method. Sometimes the rings are stuck in place with lacquer. I use some acetone to dissolve the lacquer.

You have the back apart enough to grab the flat black ring around the rear element and unscrew that group too. That should give you access to both sides of the aperture assembly. It is possible to get the whole assembly out and take all the blades out, but I don't remember the exact steps.

07-09-2009, 09:24 AM   #9
Veteran Member
yyyzzz's Avatar

Join Date: Mar 2009
Location: Salt Lake City, UT
Photos: Gallery
Posts: 509
Original Poster
fugus or what?

Thanks a lot. I will follow the steps. But are these dots fungus or what? They do not seem to have great effect on the picture quality.
07-09-2009, 01:12 PM   #10
Senior Member
wavecurrent's Avatar

Join Date: Jul 2007
Location: Kiruna, Sweden
Posts: 147
QuoteOriginally posted by yyyzzz Quote
Thanks a lot. I will follow the steps. But are these dots fungus or what? They do not seem to have great effect on the picture quality.
Sorry, can't help on that. First time I have seen it!?

Mike
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!
apertures, k-mount, lens, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
macro advice wanted for low apertures (e.g. f/22) noou Pentax SLR Lens Discussion 18 09-13-2010 08:19 AM
Apertures of M lenses: 28/2.8, 50/1.7 & 135/3.5 Jonathan Mac Pentax SLR Lens Discussion 3 01-31-2010 01:35 PM
Lens "haze" worse at certain apertures? panoguy Pentax SLR Lens Discussion 7 11-24-2009 04:22 PM
K20d + Sigma 50mm 1.4: frontfocus only at large apertures chrisg Pentax DSLR Discussion 15 10-30-2009 08:03 AM
Help: manual apertures won't adjust mediaslinky Pentax DSLR Discussion 6 03-31-2009 07:14 AM



All times are GMT -7. The time now is 10:54 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