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Nikon 12-24mm AF back focus?
#1
I just took the plunge and bought a second hand 12-24mm on eBay... seemed like too good an oppportunity as it wasn't up for auction but 'Buy it now' at £550 instead of £750-800 new... only way I was going to be able to afford this lens.

I thought I'd take the risk, check it very quickly for decentering and resolution and send it back straight away if any problems.



Lens arrived on Tuesday and I've been at work all week so no opportunity to get out with the lens, but I have tested for decentering (using your sanity check, Klaus - thanks again! <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='Smile' />) and it seems fine in that respect - I couldn't see any issues at all. Also looks good as new - not a mark on it.



A B&W F-Pro 010 filter was also incuded in the price... maybe I should have been more suspicious.. or on the other hand, maybe I'm being over-anxious about it now!



I think the lens is auto-focusing behind the intended focus point (aka "back-focusing"?)

I've spent several hours today trying to suss out whether this is really the case, and how much AF micro-adjust to apply.

I've now read several articles, and have focus tool by Tim Jackson, came across idea of lining up batteries at a 45 degree angle and making small changes to the MF adjust, looked at LensAlign (seems v. expensive) and have taken numerous pics, some in poor light... and am really no nearer to getting this sorted. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/huh.gif' class='bbc_emoticon' alt='Huh' />



Pics [url="http://iancds.smugmug.com/Tests/TEST-Nikon-12-24/19671189_b9tn3J#1543100152_JKXnWdS"]here[/url]. Camera is Nikon D7000, focal length used = 12mm @ f4. Clicking on the images should bring up option to view them at original size ('O').

In all cases, I used single-servo AF, with one focus point at the centre of the image. I appreciate some of these are much less useful than others for looking at this issue... some pointers to selected focus points:
  • Cat's eye was selected point of focus (not the dried blades of grass & ivy behind)
  • View looking up at the house: focus point is centre (in line with window centres), 3rd course of stones above patio doors. Focus seems to me to improve higher up the stone wall (again, farther away)
  • Teasel: front of cone was focus point
  • Dried out flowers in flower bed: front of foremost seedhead
I'd be very grateful for

  1. suggestions re the best way to find optimum AF micro-adjust setting - or if the lens focus might be too far out of spec so that it needs Nikon to adjust (and I say bye bye to the £ saving..!)
  2. whether getting micro-adjust right at 12mm will work through zoom range - if not, is it possible to save different AF m-a settings to use at different focal lengths on the same lens - I don't think it is?
  3. whether the overall image quality is in line with what I should expect from this lens... or should I send it back fast on Monday..?! <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='Sad' />
Ian
  


Messages In This Thread
Nikon 12-24mm AF back focus? - by IanCD - 10-22-2011, 08:59 PM
Nikon 12-24mm AF back focus? - by anyscreenamewilldo - 10-23-2011, 08:29 AM
Nikon 12-24mm AF back focus? - by Rainer - 10-23-2011, 09:18 AM
Nikon 12-24mm AF back focus? - by IanCD - 10-23-2011, 03:17 PM
Nikon 12-24mm AF back focus? - by arvydas - 10-23-2011, 06:51 PM
Nikon 12-24mm AF back focus? - by IanCD - 10-23-2011, 07:32 PM
Nikon 12-24mm AF back focus? - by Brightcolours - 10-23-2011, 07:41 PM
Nikon 12-24mm AF back focus? - by IanCD - 10-23-2011, 09:44 PM
Nikon 12-24mm AF back focus? - by Guest - 10-23-2011, 10:10 PM
Nikon 12-24mm AF back focus? - by IanCD - 10-24-2011, 09:25 PM
Nikon 12-24mm AF back focus? - by IanCD - 11-06-2011, 12:24 AM
Nikon 12-24mm AF back focus? - by Steinar1 - 11-06-2011, 10:34 AM
Nikon 12-24mm AF back focus? - by wim - 11-06-2011, 08:21 PM
Nikon 12-24mm AF back focus? - by IanCD - 11-06-2011, 09:30 PM
Nikon 12-24mm AF back focus? - by anyscreenamewilldo - 11-08-2011, 11:42 AM
Nikon 12-24mm AF back focus? - by arvydas - 11-08-2011, 01:02 PM
Nikon 12-24mm AF back focus? - by IanCD - 12-07-2011, 11:16 PM
Nikon 12-24mm AF back focus? - by Guest - 12-08-2011, 09:45 AM
Nikon 12-24mm AF back focus? - by IanCD - 12-09-2011, 11:59 AM
Nikon 12-24mm AF back focus? - by Guest - 12-09-2011, 12:41 PM
Nikon 12-24mm AF back focus? - by IanCD - 12-09-2011, 07:21 PM
Nikon 12-24mm AF back focus? - by wim - 12-09-2011, 10:26 PM
Nikon 12-24mm AF back focus? - by IanCD - 12-10-2011, 10:46 AM

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