AF Fine Adjustment - Live View

theWags · 04-28-2014, 09:22 AM

Does anyone know if there is a different method for AF fine adjustment for live few vs standard view? I have an adjustment chart and in live view this particular lens appears to be excessively front focused, while in standard view it focuses perfectly. Yet when I use the fine adjustment menu, it has absolutely no effect on the live view focus. I can go +10 or -10 and it has no effect. This is on a K-3 body with a Pentax 18-250 lens. I'll check through the manual some more, but just wondering if any of you know what's up.

Thanks,
Will

**jatrax** · 04-28-2014, 09:58 AM

There is no adjustment for Liveview AF. The AF fine tuning only works on the view finder focusing system. The theory is that Live view cannot be out of adjustment as it uses the sensor itself to focus. I don't know if that is 100% true, but I have never found a lens that was not accurate using Live view.

theWags · 04-28-2014, 10:29 AM

Originally posted by jatrax

There is no adjustment for Liveview AF. The AF fine tuning only works on the view finder focusing system. The theory is that Live view cannot be out of adjustment as it uses the sensor itself to focus. I don't know if that is 100% true, but I have never found a lens that was not accurate using Live view.

Well, that explains a lot. Thanks! I have been playing a bit and found some interesting results. When I use spot focus, LV is right on. When I use multiple points, even though I'm focusing on a small flat chart on the wall several feet away, LV is very out of focus. Can't even read the letters. Same with tracking, out of focus. All done with tripod, IR remote trigger.

lytrytyr · 04-28-2014, 11:01 AM

Originally posted by jatrax

I have never found a lens that was not accurate using Live view.

Two separate optical effects, field curvature and focus shift,
could cause live view CDAF to become inaccurate.

**jatrax** · 04-28-2014, 11:15 AM

Originally posted by theWags

When I use spot focus, LV is right on.

I never use anything except spot focus which might explain why I never saw any issues. Maybe I'm not thinking straight but would you not want to use center point when testing a lens? I would think multi-point would have the chance of introducing other variables. But then I use a lens-align device not a flat chart so that might be different.

**grahame** · 04-28-2014, 01:27 PM

Originally posted by jatrax

I never use anything except spot focus which might explain why I never saw any issues.

I actually saw quite a few 3rd party lenses had AF accuracy issue on K-01, and I also saw quite a lot threads post here complaining AF issue on K-01. Tamron 28-75 is one of them gets a lot complain.

I have tested many time, and have excluded the possibilities of AF point selection and SR related problems. And usually more obvious when the lens is stop down than wide open, unless the DOV is wide enough to cover the problem.

And it is not 3rd party lenses only. My DA55/1.4 has similar but much minor BF on K-01. The lens is very very sharp even wide open, but I was surprised to see less so at F 1.8 and 2 on K-01.

interestingly, live view (contrast detection) AF on K5II is just fine. I noticed this problem on K-01 only. I even returned a K-01 for that reason but the 2nd came with same problem. I use small primes on K-01 only so not an issue for me. Apparently, the AF chip on the camera could make mistake, even using live view.

lytrytyr · 04-28-2014, 01:47 PM

Originally posted by grahame

My DA55/1.4 has similar but much minor BF on K-01. The lens is very very sharp even wide open, but I was surprised to see less so at F 1.8 and 2 on K-01.

That sounds like focus shift.

**grahame** · 04-28-2014, 01:55 PM

Originally posted by lytrytyr

That sounds like focus shift.

That was what I thought. But strangely it happens on K-01 only. On K5II, it is just fine with both phase (with a little AF adjust) and contrast section AF. I expect same behavior on both if it was focus shift . Plus, if I manually focus them on K-01, with small F, focus is always fine. So I will say probably not focus shift. It is rather an AF calculation issue, and somehow, someone 3rd lens are not being able to talk to camera appropriately.

04-28-2014, 09:22 AM	#1
theWags Closed Account Join Date: Aug 2012 Location: Arizona Posts: 46	AF Fine Adjustment - Live View Does anyone know if there is a different method for AF fine adjustment for live few vs standard view? I have an adjustment chart and in live view this particular lens appears to be excessively front focused, while in standard view it focuses perfectly. Yet when I use the fine adjustment menu, it has absolutely no effect on the live view focus. I can go +10 or -10 and it has no effect. This is on a K-3 body with a Pentax 18-250 lens. I'll check through the manual some more, but just wondering if any of you know what's up. Thanks, Will

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04-28-2014, 09:58 AM	#2
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	There is no adjustment for Liveview AF. The AF fine tuning only works on the view finder focusing system. The theory is that Live view cannot be out of adjustment as it uses the sensor itself to focus. I don't know if that is 100% true, but I have never found a lens that was not accurate using Live view.

04-28-2014, 10:29 AM	#3
theWags Closed Account Join Date: Aug 2012 Location: Arizona Posts: 46 Original Poster	Originally posted by jatrax There is no adjustment for Liveview AF. The AF fine tuning only works on the view finder focusing system. The theory is that Live view cannot be out of adjustment as it uses the sensor itself to focus. I don't know if that is 100% true, but I have never found a lens that was not accurate using Live view. Well, that explains a lot. Thanks! I have been playing a bit and found some interesting results. When I use spot focus, LV is right on. When I use multiple points, even though I'm focusing on a small flat chart on the wall several feet away, LV is very out of focus. Can't even read the letters. Same with tracking, out of focus. All done with tripod, IR remote trigger.

04-28-2014, 11:01 AM	#4
lytrytyr Pentaxian Join Date: Nov 2011 Photos: Gallery \| Albums Posts: 4,310	Originally posted by jatrax I have never found a lens that was not accurate using Live view. Two separate optical effects, field curvature and focus shift, could cause live view CDAF to become inaccurate.

04-28-2014, 11:15 AM	#5
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Originally posted by theWags When I use spot focus, LV is right on. I never use anything except spot focus which might explain why I never saw any issues. Maybe I'm not thinking straight but would you not want to use center point when testing a lens? I would think multi-point would have the chance of introducing other variables. But then I use a lens-align device not a flat chart so that might be different.

04-28-2014, 01:27 PM	#6
grahame Loyal Site Supporter Join Date: Aug 2011 Photos: Albums Posts: 2,041	Originally posted by jatrax I never use anything except spot focus which might explain why I never saw any issues. I actually saw quite a few 3rd party lenses had AF accuracy issue on K-01, and I also saw quite a lot threads post here complaining AF issue on K-01. Tamron 28-75 is one of them gets a lot complain. I have tested many time, and have excluded the possibilities of AF point selection and SR related problems. And usually more obvious when the lens is stop down than wide open, unless the DOV is wide enough to cover the problem. And it is not 3rd party lenses only. My DA55/1.4 has similar but much minor BF on K-01. The lens is very very sharp even wide open, but I was surprised to see less so at F 1.8 and 2 on K-01. interestingly, live view (contrast detection) AF on K5II is just fine. I noticed this problem on K-01 only. I even returned a K-01 for that reason but the 2nd came with same problem. I use small primes on K-01 only so not an issue for me. Apparently, the AF chip on the camera could make mistake, even using live view.

04-28-2014, 01:47 PM	#7
lytrytyr Pentaxian Join Date: Nov 2011 Photos: Gallery \| Albums Posts: 4,310	Originally posted by grahame My DA55/1.4 has similar but much minor BF on K-01. The lens is very very sharp even wide open, but I was surprised to see less so at F 1.8 and 2 on K-01. That sounds like focus shift.

04-28-2014, 01:55 PM	#8
grahame Loyal Site Supporter Join Date: Aug 2011 Photos: Albums Posts: 2,041	Originally posted by lytrytyr That sounds like focus shift. That was what I thought. But strangely it happens on K-01 only. On K5II, it is just fine with both phase (with a little AF adjust) and contrast section AF. I expect same behavior on both if it was focus shift . Plus, if I manually focus them on K-01, with small F, focus is always fine. So I will say probably not focus shift. It is rather an AF calculation issue, and somehow, someone 3rd lens are not being able to talk to camera appropriately.