Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-23-2009, 01:53 AM   #1
Senior Member
pdxbmw's Avatar

Join Date: Sep 2008
Location: Portland, OR
Posts: 218
FA 28-105mm power zoom question

I just picked up this lens and I can only manually zoom. K10D with only power zoom at the low end or the high end, but gets stuck from 35 to 80. Feels tight when manually zooming in this range. Any ideas? I have never used a power zoom lens before, so it is not necessary but seems like a cool little feature.

Patrick

08-23-2009, 02:32 AM   #2
Veteran Member
MattGunn's Avatar

Join Date: Jun 2009
Location: Wales
Photos: Gallery
Posts: 347
I have one of these, on a DSLR the power zoom is just a gimic really but it is a nice (if a little heavy) lens and takes good pictures. It sounds like the zoom is just too stiff in the mid range for the power zoom motor to cope with. It may have ingested some sand or something (I have removed sand from several overly stiff zooms now, and they are usually much better afterwards). I have not tried opening this lens but others have as described here:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/68648-fa-zooms...endations.html
and here
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/63745-screw-dr...us-inside.html
08-23-2009, 06:05 AM   #3
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
you may have internal wear on the zoom cams.

if you look at this lens, (and many other pentax zooms) the optical formula has the minimum lens length (physically) in the middle of the zoom range, with the lens growing longer at both focal length extremes.

It is possible that the lens can get stalled at this point. You will probably note, if you zoom manually that the stiffness changes on the zoom collar at this point. Try zooming with the lens pointing streight up and streight down also, to see what impact gravity has on the problem.
08-23-2009, 01:07 PM   #4
Senior Member
pdxbmw's Avatar

Join Date: Sep 2008
Location: Portland, OR
Posts: 218
Original Poster
I took it apart as far as I could get, put it back together and it works, not great but it works.

08-23-2009, 01:20 PM   #5
Veteran Member
MattGunn's Avatar

Join Date: Jun 2009
Location: Wales
Photos: Gallery
Posts: 347
Well done, have you tried repairing lenses before? Any operation which ends with an improvement is a sucess
08-24-2009, 03:06 PM   #6
Senior Member
pdxbmw's Avatar

Join Date: Sep 2008
Location: Portland, OR
Posts: 218
Original Poster
I have taken one or two lenses apart. I figure it is not rocket science, the hard part is keeping all the screws in place and getting that damn ball bearing back in for the aperture ring.
08-25-2009, 12:03 PM   #7
Veteran Member
MattGunn's Avatar

Join Date: Jun 2009
Location: Wales
Photos: Gallery
Posts: 347
Oddly enough, from a physicists point of view, well corrected imaging lenses are a lot more complicated than rocket science
Putting lenses back together (especially if you want them to work / focus to infinity etc) is undoubtely harder than taking them apart. Getting the ball from the aperture back in can be a pane in the **** and when you hear it ping of across the room in can be very difficuly to find it again... I found a small ball race with suitable sized balls in and dismantled it to get a good supply of spares.
Fixing lenses can be quite satisfying and can save you a fortune. I got a broken tamron 70-300 for 20 and had it fixed in under an hour
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, lens, pentax lens, power, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: SMC Pentax-FA 28-105mm F4-5.6 Power Zoom Lens tsiklop Sold Items 1 01-05-2010 04:16 PM
For Sale - Sold: Pentax 28-105mm f 4-5.6 power zoom skinja Sold Items 5 08-29-2009 07:51 PM
For Sale - Sold: Pentax-FA SMC AF 28-105mm 4-5.6 Power Zoom woof Sold Items 2 10-25-2008 07:53 PM
pentax-fa power zoom 28-105mm f4-5.6 Grizm Pentax SLR Lens Discussion 5 08-21-2007 12:45 PM
Dumb question: what exactly is power zoom? okto Pentax SLR Lens Discussion 6 11-11-2006 01:07 PM



All times are GMT -7. The time now is 03:39 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