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The Sigma 14mm f/1.8 ART ...
#17
Quote:I reckon it is caused by the camera not being able to determine exactly what to use for AF exactly, as the AF points cover quite a bit more territory than they do with e.g. tele-lenses. Having a slower aperture helps a lot in those cases, I would think.

 

 
Almost never, there is something a lot in front of what you want to focus on with UWA lenses. It can be that you focus on a small target where behind it the background can become a target of the AF point. However, AF points are small enough to rule that out in tests. 

 

Spherical aberrations in a lens can throw off the PD AF system, depending on which colours the AF sensor is sensitive to. And the steps a lens makes can also be an issue.

In this case, from what Klaus describes, I suspect aberrations to be the/a culprit. Testing my 10-18mm on 14mm yesterday in MF, the focus confirmation range was very, very small.
  


Messages In This Thread
The Sigma 14mm f/1.8 ART ... - by Klaus - 11-04-2017, 01:53 AM
The Sigma 14mm f/1.8 ART ... - by Klaus - 11-06-2017, 12:44 AM
The Sigma 14mm f/1.8 ART ... - by Brightcolours - 11-06-2017, 06:26 AM
The Sigma 14mm f/1.8 ART ... - by Klaus - 11-06-2017, 08:13 AM
The Sigma 14mm f/1.8 ART ... - by davidmanze - 11-06-2017, 09:24 AM
The Sigma 14mm f/1.8 ART ... - by JJ_SO - 11-06-2017, 09:53 AM
The Sigma 14mm f/1.8 ART ... - by Brightcolours - 11-06-2017, 10:00 AM
The Sigma 14mm f/1.8 ART ... - by davidmanze - 11-06-2017, 10:15 AM
The Sigma 14mm f/1.8 ART ... - by Klaus - 11-06-2017, 11:11 AM
The Sigma 14mm f/1.8 ART ... - by JJ_SO - 11-06-2017, 11:30 AM
The Sigma 14mm f/1.8 ART ... - by Brightcolours - 11-06-2017, 12:41 PM
The Sigma 14mm f/1.8 ART ... - by JJ_SO - 11-06-2017, 01:40 PM
The Sigma 14mm f/1.8 ART ... - by Rover - 11-06-2017, 03:25 PM
The Sigma 14mm f/1.8 ART ... - by wim - 11-07-2017, 12:53 AM
The Sigma 14mm f/1.8 ART ... - by Rover - 11-07-2017, 07:56 AM
The Sigma 14mm f/1.8 ART ... - by JJ_SO - 11-07-2017, 08:30 AM
The Sigma 14mm f/1.8 ART ... - by Brightcolours - 11-07-2017, 09:24 AM
The Sigma 14mm f/1.8 ART ... - by Rover - 11-07-2017, 05:27 PM
The Sigma 14mm f/1.8 ART ... - by JJ_SO - 11-07-2017, 06:02 PM

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