Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-17-2012, 12:51 AM   #1
Senior Member
Patajac's Avatar

Join Date: Jan 2012
Posts: 241
Zoom lens Focus adjustement

I have a problem with Tamron 17-50 2.8 on K5 where it needs -3 adjustment at 50mm, -1 at 35mm and +5 at 17mm.

This was tested with focus test chart, daylight, tripod, SR off etc etc...

If i leave AF adjustment off, nothing is in perfect focus at 100% view at any aperture and if i adjust for perfect focus at 50mm back focusing at 17mm becomes severe.

Is this reparable if i send it in?

07-17-2012, 04:17 AM   #2
Veteran Member




Join Date: Jul 2009
Location: London
Posts: 856
QuoteOriginally posted by Patajac Quote
.

Is this reparable if i send it in?
The lens or the camera?

Tried averaging the correction?
07-17-2012, 04:35 AM   #3
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
Note that many newer zooms change the focal length as part of the zooming process, therefore it is not optically he same glass at 5 meters and infinity

Aosn note that at a distance, camera shake can have you focusing on foreground as opposed tonthe subject itself. Do you do this on a tripod or hand held?
07-17-2012, 07:35 AM   #4
Senior Member
tlwyse's Avatar

Join Date: Aug 2008
Location: Waxhaw, NC, USA
Photos: Gallery | Albums
Posts: 208
That's interesting because I just completed a series of focus tests last week with this exact lens on my K20D and using the LensAlign focus tool. I tested at the same focal lengths as you....17, 35 and 50mm....and I tested at distances of both 25x and 50x focal length (I always test at -1 stop from wide-open). What I got back was consistently +8 to +10 adjustments. I did a few other lenses and came back with anywhere from +6 to +10 on all lenses. My conclusion, at least with *my* K20D, is that AF adjustment is more about correcting the camera body than individual lenses.

07-17-2012, 08:14 AM   #5
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
QuoteOriginally posted by tlwyse Quote
That's interesting because I just completed a series of focus tests last week with this exact lens on my K20D and using the LensAlign focus tool. I tested at the same focal lengths as you....17, 35 and 50mm....and I tested at distances of both 25x and 50x focal length (I always test at -1 stop from wide-open). What I got back was consistently +8 to +10 adjustments. I did a few other lenses and came back with anywhere from +6 to +10 on all lenses. My conclusion, at least with *my* K20D, is that AF adjustment is more about correcting the camera body than individual lenses.
I think there are two things here, I agree, that there can be an overall body error, and your data suggests about + 8 would be a good setting and you may wish to set it to that. not sure on the K20 whether it jhas one or multiple settings, but the K7 and K5 have options for single settings or multiple, if you had this situation on either of those bodies, i would set the camera to +9 and then modify specific lenses between +6 and +10 as needed, the general setting would apply any time the camera did not have a specific lens it recognized as being set differently.
07-17-2012, 08:18 AM   #6
Loyal Site Supporter
imtheguy's Avatar

Join Date: Mar 2009
Location: Virginia Beach
Photos: Gallery | Albums
Posts: 2,950
Answer about sending it in - ...To an extent, a factory calibration will help. I had same issue with Tammy 70-200/2.8 and used the warranty to request calibration. When it came back the adjustments required for 70, 135 and 200mm were much, much closer and I was able to settle on a single AF micro-adjustment at 135mm that keeps the focus within a typical range for any focal length at f2.8.

Yes, if in warranty its a no brainer to try. If not warranty, your call based on cost.
07-17-2012, 10:27 AM   #7
Senior Member
Patajac's Avatar

Join Date: Jan 2012
Posts: 241
Original Poster
QuoteOriginally posted by imtheguy Quote
Answer about sending it in - ...To an extent, a factory calibration will help. I had same issue with Tammy 70-200/2.8 and used the warranty to request calibration. When it came back the adjustments required for 70, 135 and 200mm were much, much closer and I was able to settle on a single AF micro-adjustment at 135mm that keeps the focus within a typical range for any focal length at f2.8.

Yes, if in warranty its a no brainer to try. If not warranty, your call based on cost.
thanks

thats what i needed to know

since it is under warranty off it goes for calibration

ps i dont have problems with other lenses
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!
17mm, 50mm, adjustment, focus, 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: auto focus zoom lens mellamojay Sold Items 6 05-12-2012 03:58 PM
After upgrade firmware for K5, Should I need to re-do focus adjustement ?? jacpat Pentax K-5 4 10-18-2011 09:15 AM
Can ME-SUPER use an Auto Focus (AF) zoom lens? prometheis_78063 Pentax SLR Lens Discussion 11 06-30-2011 02:00 PM
Pentax 18-135 Lens Focus through Zoom Range nstocke Pentax SLR Lens Discussion 3 02-06-2011 10:47 AM
new K7 - focus adjustement - confused Walter K Pentax DSLR Discussion 4 12-28-2009 01:16 AM



All times are GMT -7. The time now is 03:21 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