Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-19-2015, 10:25 AM   #1
Senior Member




Join Date: Jul 2012
Location: Trondheim
Posts: 234
Slow Aperture on D-FA 100mm

Hello folks.


I discovered today that the aperture lever on my D-FA 100mm Macro is quite slow. Using a flashlight i can not see any oil or other foreing substances on the Aperture blades themselves. I believe it is mechanical friction in the lever mechanism. It is not sticky, just slow.


I have removed the mount of a MF lens before (Auto Chinon 135mm F2.8) with no trouble putting it back together, but I'm a bit hesistant to do this on an AF lens. Do anyone have experience in opening up an AF lens with WR?


My intention is to very carefully lubricate the moving parts in the lever mechanism.




Best regards Tim

09-19-2015, 10:40 AM   #2
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 9,843
Typically the advice I see on manual focus lenses is to carefully clean with naphtha or similar solvents and then relubricate. Not sure if naphtha is ok with modern lenses due to the plastic parts. Someone else should know more details.
09-19-2015, 10:58 AM   #3
Senior Member
j0n4hpk's Avatar

Join Date: Apr 2009
Location: California
Photos: Gallery | Albums
Posts: 196
Before proceeding timcatn, check if the lens needs any aperture lubricant at all. I've heard that lubricants leaking from focusing or zoom mechanisms (in case of zoom lenses) of lenses can actually stick up the aperture mechanism. I hope you success in whatever you decide to do
09-19-2015, 12:06 PM   #4
Pentaxian
dcshooter's Avatar

Join Date: Jan 2011
Location: Washington DC
Photos: Gallery | Albums
Posts: 4,607
The oil is not always visible. Naphtha has been fine for all the FA lenses I've worked on. It's recommended to remove both the front and rear groups in order to clean the blades

On AF lenses like this, there are several small contact springs that can easily get lost/misplaced. If you decide to take the whole mount off, be very careful while removing it and take a picture of the spring positions. You might actually be able to get by on this one by just removing the matte black baffle, which should give you enough room to remove the rear group.

The front group might be tricky due to the how deeply recessed it is. Not sure about the 100, but on the 50mm, there is a conical front baffle that you have to remove prior to taking out the group.

---------- Post added 09-19-15 at 12:08 PM ----------

Also, if it does turn out to be the lever, clean the bearing surface off with naphtha and apply one drop, NO MORE, of light machine oil to re-lubricate it.

09-19-2015, 11:17 PM   #5
Veteran Member




Join Date: Jun 2010
Location: Marina CA
Posts: 344
Sometimes the aperture lever is slow it is because it is bent. Compare it to one of your other lenses. Generally it gets bent toward the middle of the lens. If it is bent in it generally is not too difficult to bend it back and things will move smoothly again.
09-20-2015, 02:48 AM   #6
Pentaxian
simon_199's Avatar

Join Date: Oct 2014
Posts: 362
Mine has the same problem, and i did some searches in the past on the forum and found a couple of thread mentioning the same issue. It seems that it is a relatively common occurrence with this lens

This thread for example

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/209261-pent...ky-blades.html

contains some useful information.

I have not attempted to repair (or get repaired) mine, since actual problems (overexposure) only show up at fast burst rate and very small apertures (past f/16), however when operating the aperture lever by hand it is evident that it is not as snappy as it should be.
09-21-2015, 06:47 AM   #7
Senior Member




Join Date: Jul 2012
Location: Trondheim
Posts: 234
Original Poster
Thanks for the tips everyone.


I ended up going for it. I removed the lens mount. I could not see any errors so i slightly moved the starting position of the lever. Effectivly tightening the spring a small amount. The drawback of this is of course that i might have skewed the f-stops slightly (depening if it was correct to begin with). Will test when i get home from work. The operation was fairly simple and took around 30min.




-Tim
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!
100mm, af, aperture, camera, d-fa, front, lens, lenses, lever, mechanism, oil, pentax help, photography, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
D-fa 100mm wr shaolen Pentax SLR Lens Discussion 8 02-12-2015 05:00 PM
Wanted - Acquired: Pentax 100mm 2.8 macro, F, FA, D-FA, D-FA wr rwingsfan Sold Items 2 04-28-2014 01:23 PM
Short comparaison 100mm Macro D-FA vs NEW D-FA WR fourmiX Pentax SLR Lens Discussion 36 03-12-2010 09:48 PM
Square lens hood on D FA 100mm macro audiobomber Pentax SLR Lens Discussion 3 11-19-2008 06:24 PM



All times are GMT -7. The time now is 12:31 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