Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Feb 19, 2012, 10:19 AM   #1
Senior Member
 
Join Date: Apr 2010
Posts: 447
Default Back focusing?

Sometimes it pays not to get involved some issues. After doing some reading on different blogs about problems concerning the back focusing issues claimed by D7000 users, I ran a test of sorts on my own. Lining up five double A batteries on my desk, three inches apart, running from front to back I prceeded to shoot them, from four feet distance with different lenses targeting the center one to see what was up with this claim. All shots were taken in Single servo with flash. What I found was that the only two lenses that would nail the center battery was the Nikon 85mm 1.8 and the Tamron 28-75mm 2.8. The Nikon 35mm 1.8 and both 50mm 1.8 and 1.4 along with Tamrons 17-50mm 2.8 VR would nail the forth battery back consistantly, leaving the target battery slightly out of focus. My D-90 seemed to fair better as the 50mm 1.4 would again nail the center one. Switching to the D-700, all FX lenses in this group would focus on the center battery and nail the subject. Going through a few of my past pics I cant detect this issue cropping up. Perhaps its a light quality problem, where through poor contrast of subject and foreground confuses the system. I will have to try this outside where the lighting is better.
emptyquiver is offline   Reply With Quote
Sponsored Links
Old Feb 19, 2012, 10:36 AM   #2
Super Moderator
 
peripatetic's Avatar
 
Join Date: Nov 2004
Posts: 3,599
Default

First read the article explaining why these things happen.

http://www.luminous-landscape.com/re...ensalign.shtml

The D7000 allows you to self-calibrate and adjust your lenses to your camera. Just sort it out, nothing to worry about.
__________________
My gallery
My X100 blog
peripatetic is offline   Reply With Quote
Old Feb 19, 2012, 11:10 AM   #3
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

Instead of the batteries, try the Focus Test Chart.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old Feb 19, 2012, 2:48 PM   #4
Senior Member
 
Join Date: Apr 2010
Posts: 447
Default

Thanks guys.....this ought to be fun (like unplugging a sewer drain). TCav I will print out and try your approach tonight and if, in fact it is the lack of technique on my behalf this should prove it out. If in fact it maybe a back focusing issue then Peripatetics suggestion would make a good tool to have. I knew I shouldnt of ventured here as nothing had rung any alarm bells except for the 35mm 1.8 which I found unsatisfing considering all the good reviews concerning it. Both these articles are imformitive and I will give it a go. Thanks again. EQ.
emptyquiver is offline   Reply With Quote
Old Feb 19, 2012, 2:59 PM   #5
Super Moderator
 
peripatetic's Avatar
 
Join Date: Nov 2004
Posts: 3,599
Default

You don't have to buy a Lensalign kit.

Just a bit of trial & error for you different lenses at you most common working distances ( to allow for focus shift) dial in an adjustment, shoot, check on screen at 100%, repeat until you find what works for you. Then set your camera accordingly. Should only take 10 mins per lens.
__________________
My gallery
My X100 blog
peripatetic is offline   Reply With Quote
Old Feb 19, 2012, 4:11 PM   #6
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

It is possible that one or both cameras might be slightly off, and it is possible that one or more of your lenses might be slightly off. In fact some combination of both possibilities is quite likely.

I wouldn't do anything to any camera or any lens until I knew the whole story.

It sounds to me like what you've already done indicates a very slight difference between the two bodies, and a slight variation within your collection of lenses. All of this is not unexpected, but I suggest you procede with caution.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old Feb 19, 2012, 7:27 PM   #7
Senior Member
 
Join Date: Apr 2010
Posts: 447
Default Focus test...

..of sorts. Shot as instructed. 1st is Tamrons 28-75mm 2.8 at 50mm. Second is same lens at 75mm. Third is Tamrons 17-50 mm 2.8 at 50mm. Forth is Nikons 35mm 1.8. Fifth is Nikons 85mm 1.8. I took multiple shoots with each lens, and what is shown here is a representation of each lens. Primes were shoot at widest apetiture and teleys were shot at max focal length and widest apetiture.
Attached Images
     
emptyquiver is offline   Reply With Quote
Old Feb 19, 2012, 8:30 PM   #8
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

... on which body?
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old Feb 19, 2012, 8:33 PM   #9
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

I would like to have seen the Tamron 17-50/2.8 at 35mm. (... and maybe the 28-75 too.)
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old Feb 19, 2012, 9:27 PM   #10
Senior Member
 
Join Date: Apr 2010
Posts: 447
Default

D-7000 body TCav.....I can do it at 35mm....what the hell this is getting interesting to say the least. I think I will repeat the same lenses on a different body also.
emptyquiver is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 8:33 AM.