Consistent front focus wierdness
/forum/topic/1069294/0



mark petri
Registered: Oct 25, 2006
Total Posts: 1006
Country: United States

Well the new 5d markII arrived and while i'm not normally a pixel peeper, I did some shots of the trusty ruler while on the tripod, center point AF, etc @ 45 degrees. Just about every lens was front focusing by around 1/2". Never noticed it with my prior body (Dsmk3),but then again never really looked for it either. Wondering if it's the body AF ior all my lenses are off now... opened a can of worms.



rscheffler
Registered: Aug 23, 2005
Total Posts: 5051
Country: Canada

If it's consistently in front, then there's not much weirdness going on, you probably just need to MFA it. But I'd suggest first using it in a variety of situations common for you, checking the images for any issues, then deciding whether or not to MFA.



mark petri
Registered: Oct 25, 2006
Total Posts: 1006
Country: United States

Correct me if I'm wrong, MFA is at least in theory is intended to dial-in small AF adjustments due deviations in AF on a per lens basis correct?

If so, I find it had to believe 8 or so different lenses all being off by roughly the same amount, thus I was guessing it would likely be the body and not the lens. Yes, of course if they are all off by x, I can dial in by that mount to solve the symptom (assuming it's consistent when stopped down), but was speculating more on the root cause.



TrojanHorse
Registered: Apr 04, 2008
Total Posts: 2747
Country: United States

Mine all seem to be off by +5 although one is +10 and one is about 0.

It doesn't take much to be "off" by +5, I'd just set your lenses and carry on. If they were all +20 I'd worry.



mark petri
Registered: Oct 25, 2006
Total Posts: 1006
Country: United States

Ya, you gents are right- I suspect that in my normal shooting, i would hardly if at all notice it. Cheers!



scalesusa
Registered: Sep 02, 2008
Total Posts: 2487
Country: United States

If all lenses are off, you can adjust the MA for the body and all lenses will be adjusted. Its not just for adjustment of individual lenses. The calibration of each body can vary, so use the tool provided and your images will be what you expect.



Ferrophot
Registered: Jun 11, 2010
Total Posts: 341
Country: Australia

Yes, you can adjust MA for all lenses or for each individual lens. My camera seems to need a consistent +6, but there are some small variations from this for one or two individual lenses. I didn't use the "all lenses" adjustment, I did each one individually.



BrianO
Registered: Aug 21, 2008
Total Posts: 8552
Country: United States

mark petri wrote: ...I find it had to believe 8 or so different lenses all being off by roughly the same amount, thus I was guessing it would likely be the body and not the lens.

You are correct. It could be from a manufacturing tolerance in the lens mount, a difference in the distance of the AF sensor versus the image plane, etc.

Whatever the cause, though, unless it's extreme you can correct it with MFA rather than sending in the body for recalibration.