Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-21-2013, 08:12 PM   #1
Pentaxian
MSL's Avatar

Join Date: Feb 2012
Location: Greater Toronto Area
Photos: Albums
Posts: 3,409
How to test second hand AF lens?

I'm familiar with RioRico's post on Pawn Shop lenses, and my goal here is not to re-invent all the info he accumulated there. My specific question:
If you have a chance to buy a second hand AF lens in person, how might you test to see if the AF is working well? I've seen a number of discussions of lenses that had quality issues during production, where getting a good copy was hit and miss, and the lens I'm interested in seems to fit this description. If all you have to test with is your camera, how can you be sure the focus is sharp when all you can do is zoom in using the LCD on the back.

Suggestions of any sort most welcome.

09-21-2013, 08:28 PM   #2
Pentaxian
Aegon's Avatar

Join Date: Jan 2008
Location: Portland, OR
Posts: 1,414
For screwdrive lenses: I don't think I've ever had one fail. But I had one that was sticky through a range, but it still worked.
For SDM lenses: Roll the dice. Also listen for squeaks. SDM failures occasionally show first signs of failure by requiring a warm-up period. If you have a 16-50 or 17-70 you can pretty much pen the epitaph, IMHO.
09-21-2013, 08:40 PM   #3
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 43,677
For screwdrive lenses make sure you check that there isn't too much friction in any of the rings.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

09-21-2013, 08:46 PM   #4
Site Supporter
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,825
You have two separate issues:
1) Does it work mechanically. As noted above screw drives rarely fail and SDM, well who knows. To test I would turn the lens to minimum focus and then AF on something relatively far away. Repeatedly. If it consistently locks focus, I think that's all you can do. On SDM if there are any failures or sluggishness I would be concerned.

2) Does it lock focus at the right place. In other words is the image resulting from a focus lock sharp and actually in focus. To test properly you need a good target, a tripod, good light and repeated testing. Not sure you can do that correctly in a casual test at a shop. I would try to shoot some images of a subject with good detail at several distances. And if possible take a tablet or laptop along, shoot jpeg and check on the big screen.

Front or back focus is not necessarily a reason to not buy if it is consistent and you have a camera that allows fine tuning.

I tested a DA*300 at a shop this morning. It was missing the hood and had a pretty good mark on the barrel, I assume the hood took the brunt of whatever caused the mark and suffered for it. I turned the lens to minimum focus and then focused on a sign across the shop 5 times. Focus was slow, though it eventually locked in. I looked at the images and everything seemed in focus but something just did not feel right so I passed. Maybe it was fine but gut feelings rarely lead me wrong.

Hope that helps.

09-21-2013, 11:04 PM   #5
Site Supporter
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,663
QuoteOriginally posted by jatrax Quote
1) Does it work mechanically.
I would add that the resistance should be low and the same lock-to-lock with the lens off-camera or with AF disengaged.


Steve
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!
af, hand, k-mount, lens, lenses, pentax lens, slr lens, test
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
What to look for in second hand k5 vetty Pentax K-5 4 11-25-2012 10:33 AM
Japan Second Hand Lens Prices - an UPdate bhairavp Pentax SLR Lens Discussion 2 09-01-2012 06:44 AM
To buy or not to buy: Old (second hand store) K-mount lenses? Origineelreclamebord Pentax SLR Lens Discussion 13 08-21-2012 07:44 AM
How well do Pentax cameras hold their value (second hand)? Origineelreclamebord Photographic Industry and Professionals 8 06-13-2012 09:49 PM
Second hand K20: what to check out AsahiMan Pentax DSLR Discussion 2 09-20-2009 11:29 PM



All times are GMT -7. The time now is 05:29 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