Missing focus with single-target AF: lens, camera, or user problem?

Neil Harris

Mu-43 Regular
Joined
Mar 21, 2019
Messages
38
Location
Edmonton, AB, Canada
When I'm out shooting wildflowers I frequently use my O12-40/2.8 on an E-M10 III at 40 mm for close-up shots (switching to O60/2.8 for macro shots). I use the O12-40/2.8 handheld (aperture priority, S-AF+MF) with single-target AF, but I frequently miss focus at the single-target location. The focus plane is behind the target. I've only noticed this problem with the O12-40/2.8, not with my other lenses.

I'm hoping more experienced forum members can offer some thoughts on the cause of this problem and perhaps suggest a solution or workaround.

An example of missed focus is shown below (SOOC JPG). The single AF target was on the head just beneath the eye.
Subscribe to see EXIF info for this image (if available)


100% crop with manually annotated AF target, which is based on the in-camera AF location shown in the playback histogram (zooming to 14x also centers to this location in playback).
Subscribe to see EXIF info for this image (if available)
 

Ross the fiddler

Mu-43 Hall of Famer
Joined
May 20, 2012
Messages
3,758
Location
Blue Mountains, NSW, Australia
Real Name
Ross
You or it may have moved from pressing the shutter button to when the exposure happened. Remember you are working quite close & the actual focal plain is quite narrow, so there is easy room for movement error.
 
Joined
Jul 5, 2018
Messages
376
Location
Covina, California
Your settings are fine. I believe there are other factors that may cause you to have missed focus. While the 12-40 pro has excellent macro-like abilities, it is not a true macro lens like the 60mm macro. So it could very well be you are closer to the subject than the lenses minimum focus distance. Another factor could be the size of the af box. Sometimes changing the size of the af box is all that's needed to help the camera focus better. And lastly, judging by the images shown, as Ross the fiddler mentioned, it appears you may have acquired correct focus where you wanted it but then probably moved forward a bit which pushed the focus slightly further behind the subject. I suspect the last factor to be it.
It's also a good idea to raise the aperture to a higher number to get more in focus when doing macro work so even if you miss focus slightly, the image will still be acceptable. Even if you nail focus, many still prefer more to be in focus when doing macro work since depth of field is often razor thin when doing macro work.
 
Joined
Jul 5, 2018
Messages
376
Location
Covina, California
Here's an image I took and raised the aperture all the way up to F11 to get as much of the flower in focus as possible.
Subscribe to see EXIF info for this image (if available)
 

Neil Harris

Mu-43 Regular
Joined
Mar 21, 2019
Messages
38
Location
Edmonton, AB, Canada
Thanks for the excellent feedback. Yes, I had also wondered about camera movement causing the focal plane to shift after setting focus, but I had dismissed the idea since all of missed focuses were back focusing. I guess this could mean I consistently drift slightly forward while shooting and the shallow DOF at high magnification happens to pick it up.
 

Ross the fiddler

Mu-43 Hall of Famer
Joined
May 20, 2012
Messages
3,758
Location
Blue Mountains, NSW, Australia
Real Name
Ross
Thanks for the excellent feedback. Yes, I had also wondered about camera movement causing the focal plane to shift after setting focus, but I had dismissed the idea since all of missed focuses were back focusing. I guess this could mean I consistently drift slightly forward while shooting and the shallow DOF at high magnification happens to pick it up.
It's possible, (as an example) as possible as camera rotation occurring when pressing the shutter button etc..
 

panamike

Mu-43 Hall of Famer
Joined
Jul 5, 2016
Messages
4,839
Location
Lincolnshire UK
It does happen, i had sort of given up trying to work out why, one consideration i had was its the IBS moving the sensor but on S-AF it shouldnt be a problem, this one the focus moved forward but i think i got away with it.
In the end i decided it was my movement which does not need to be much at that range.


Subscribe to see EXIF info for this image (if available)
P1010095 by electric.mike, on Flickr
 

ac12

Mu-43 All-Pro
Joined
Apr 24, 2018
Messages
1,654
Location
SF Bay Area, California, USA
Yup
I HATE hand-holding at closeup/macro distances, because it is SOOOOOO hard to keep from moving forward/backwards, which the IBIS will not compensate for. And I could move between when the camera locks focus and the shutter fires, and the subject will be OOF.
 
Links on this page may be to our affiliates. Sales through affiliate links may benefit this site.
Mu-43 is a fan site and not associated with Olympus, Panasonic, or other manufacturers mentioned on this site.
Forum post reactions by Twemoji: https://github.com/twitter/twemoji
Copyright © 2009-2019 Amin Forums, LLC
Top Bottom