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back focus where's the problem
#1
When I shoot normally looking through the viewfinder in most of the pictures the focus is before the subject, however when I use live view the focus is spot on, is it the lens or camera ?  

Other lenses are doing just fine so I guess it is a lens problem, can I solve this with 750D without sending my lens for focus calibration ?

#2
So, only one (unnamed) lens produces images with front focus. Do I understand that correctly? Then the lens needs to be calibrated/repaired.

#3
No in camera AFPD adjustment?

#4
No, and with a constantly front focussing lens one should get the lens "calibrated" anyway, even if the camera offers MFA.

#5
Quote:No, and with a constantly front focussing lens one should get the lens "calibrated" anyway, even if the camera offers MFA.
 Most of my lenses need some adjustment....

 

   What would I do with my pet elephant lens BC? it needs -2 on the D750 and -8 on the D7100....I'd keep the postal service in work for a month!
#6
Quote: Most of my lenses need some adjustment....

 

   What would I do with my pet elephant lens BC? it needs -2 on the D750 and -8 on the D7100....I'd keep the postal service in work for a month!
We can't tell how unrelated or related the -2 and -8 are. Now if you had two cameras with exactly the same AF system and sensor size, and you had -2 and -8, you'd have bigger issues.

 

And then it gets even worse when different AF points make you dial in different MFA numbers...
#7
The strange thing is that most of my other lenses follow similar AF adjustments within a small percentage.....all my adjustments are made from the center point BTW!

 

...while the images are sharp I'm a happy bunny!
#8
I'd be a happy bunny with that 500mm f4 too...

#9
Out of curiosity, which lens is it?  This is sort of a long shot, but in between shots have you look through the front element of the lens (in good light) and determined that the aperture has returned to all the way open?  You could also use the depth of field preview (with the lens set to f/8 or something.

 

I can say for sure that the live view works in mysterious ways, but it seems like you (within limits) get a preview of the exposure as it is making necessary adjustments.  So, in the situation where the diaphragm does not always open back up you will see exposure, and also focus sometimes screwed up when using the viewer, but not when using live view.

 

If it does stick, though often it is not every time.  LOL have you tried hitting it?

#10
BTW- You might worsen the problem is you set the aperture to extremely small settings, e.g. f/22, f/32, f/44.   I don't know a lot about lens repair, so this is only based on my experience that this is often the way I have seen the diaphragms get stuck in the first place. 
  


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