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Forums > Back > 5DMKIII versus 7DMKII
#81
Dave, not all CD AF algorithms or lenses are created equal. With Canon, crude lens motor systems make for crude CD AF results (probably also depending on the body model). With my 450D and Sigma 18-50mm f2.8, with "crude" DC motor, results were very uneven. Sometimes very OOF, sometimes just OOF, very sometimes more or less in focus. With the Tokina 12-24mm f4 and the even cruder AF implementation, only blurry results were possible. I blame that on the big steps that lens takes as "small step" during CD AF. CD AF looks from frame to frame if contrast has increased. If contrast has increased, focus is not reached yet. If contrast has decreased after it has increased before, the camera knows focus was reached and takes a step back, then declares focus.

 

Now if your lenses with the in-body motor also make bigger steps than for instance the best performing AF-S lenses, it can happen that the CD AF steps just happen to step over exact focus, and the camera never will know it as all it can base its conclusions on is on what was the highest contrast it actually saw.

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Messages In This Thread
5DMKIII versus 7DMKII - by toni-a - 12-16-2015, 07:28 AM
5DMKIII versus 7DMKII - by thxbb12 - 12-16-2015, 08:35 AM
5DMKIII versus 7DMKII - by davidmanze - 12-16-2015, 09:01 AM
5DMKIII versus 7DMKII - by joachim - 12-16-2015, 09:05 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-16-2015, 09:07 AM
5DMKIII versus 7DMKII - by joachim - 12-16-2015, 09:49 AM
5DMKIII versus 7DMKII - by Klaus - 12-16-2015, 10:30 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-16-2015, 11:29 AM
5DMKIII versus 7DMKII - by thxbb12 - 12-16-2015, 04:38 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-16-2015, 08:26 PM
5DMKIII versus 7DMKII - by toni-a - 12-16-2015, 08:57 PM
5DMKIII versus 7DMKII - by Ayoh - 12-17-2015, 03:52 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-17-2015, 07:23 AM
5DMKIII versus 7DMKII - by thxbb12 - 12-17-2015, 08:04 AM
5DMKIII versus 7DMKII - by davidmanze - 12-17-2015, 08:10 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-17-2015, 08:41 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-17-2015, 08:51 AM
5DMKIII versus 7DMKII - by davidmanze - 12-17-2015, 09:02 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-17-2015, 09:12 AM
5DMKIII versus 7DMKII - by davidmanze - 12-17-2015, 09:17 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-17-2015, 09:47 AM
5DMKIII versus 7DMKII - by thxbb12 - 12-17-2015, 09:54 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-17-2015, 10:47 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-17-2015, 11:38 AM
5DMKIII versus 7DMKII - by thxbb12 - 12-17-2015, 12:23 PM
5DMKIII versus 7DMKII - by joachim - 12-17-2015, 12:50 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-17-2015, 01:35 PM
5DMKIII versus 7DMKII - by goran h - 12-17-2015, 01:53 PM
5DMKIII versus 7DMKII - by thxbb12 - 12-17-2015, 02:12 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-17-2015, 02:59 PM
5DMKIII versus 7DMKII - by davidmanze - 12-17-2015, 03:02 PM
5DMKIII versus 7DMKII - by joachim - 12-17-2015, 07:01 PM
5DMKIII versus 7DMKII - by thxbb12 - 12-17-2015, 09:52 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-17-2015, 10:34 PM
5DMKIII versus 7DMKII - by thxbb12 - 12-17-2015, 11:42 PM
5DMKIII versus 7DMKII - by davidmanze - 12-18-2015, 01:31 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-18-2015, 07:08 AM
5DMKIII versus 7DMKII - by toni-a - 12-18-2015, 11:00 AM
5DMKIII versus 7DMKII - by davidmanze - 12-18-2015, 02:55 PM
5DMKIII versus 7DMKII - by toni-a - 12-18-2015, 05:27 PM
5DMKIII versus 7DMKII - by davidmanze - 12-18-2015, 08:46 PM
5DMKIII versus 7DMKII - by thxbb12 - 12-19-2015, 12:39 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-19-2015, 12:48 PM
5DMKIII versus 7DMKII - by thxbb12 - 12-19-2015, 03:30 PM
5DMKIII versus 7DMKII - by davidmanze - 12-19-2015, 07:15 PM
5DMKIII versus 7DMKII - by thxbb12 - 12-19-2015, 07:43 PM
5DMKIII versus 7DMKII - by davidmanze - 12-19-2015, 09:51 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-20-2015, 09:28 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-20-2015, 01:36 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-20-2015, 09:06 PM
5DMKIII versus 7DMKII - by Klaus - 12-20-2015, 10:20 PM
5DMKIII versus 7DMKII - by Klaus - 12-21-2015, 02:00 AM
5DMKIII versus 7DMKII - by Klaus - 12-21-2015, 02:37 AM
5DMKIII versus 7DMKII - by Guest - 12-21-2015, 08:03 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-21-2015, 10:58 AM
5DMKIII versus 7DMKII - by davidmanze - 12-21-2015, 05:27 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-21-2015, 05:36 PM
5DMKIII versus 7DMKII - by thxbb12 - 12-21-2015, 05:54 PM
5DMKIII versus 7DMKII - by davidmanze - 12-21-2015, 08:34 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-21-2015, 11:08 PM
5DMKIII versus 7DMKII - by Ayoh - 12-22-2015, 12:12 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-22-2015, 12:37 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-22-2015, 11:57 PM
5DMKIII versus 7DMKII - by davidmanze - 12-23-2015, 08:02 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-23-2015, 08:43 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-23-2015, 11:35 AM
5DMKIII versus 7DMKII - by davidmanze - 12-23-2015, 07:57 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-23-2015, 08:26 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-24-2015, 12:26 AM
5DMKIII versus 7DMKII - by thxbb12 - 12-24-2015, 12:38 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-24-2015, 06:55 AM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 11:34 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-24-2015, 12:11 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 12:51 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-24-2015, 01:09 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 01:36 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-24-2015, 02:13 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 02:40 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 03:10 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-24-2015, 04:08 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-24-2015, 06:31 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 07:28 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 07:36 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-24-2015, 08:22 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 08:43 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 08:50 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-24-2015, 09:28 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 10:04 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-24-2015, 10:46 PM
5DMKIII versus 7DMKII - by davidmanze - 12-24-2015, 11:31 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-25-2015, 12:26 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-25-2015, 01:45 AM
5DMKIII versus 7DMKII - by davidmanze - 12-25-2015, 06:59 AM
5DMKIII versus 7DMKII - by Brightcolours - 12-26-2015, 11:27 AM
5DMKIII versus 7DMKII - by Ayoh - 12-26-2015, 03:02 PM
5DMKIII versus 7DMKII - by davidmanze - 12-26-2015, 03:53 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-26-2015, 04:16 PM
5DMKIII versus 7DMKII - by davidmanze - 12-26-2015, 07:12 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-26-2015, 08:40 PM
5DMKIII versus 7DMKII - by davidmanze - 12-26-2015, 10:22 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-26-2015, 10:54 PM
5DMKIII versus 7DMKII - by Brightcolours - 12-26-2015, 11:04 PM
5DMKIII versus 7DMKII - by Ayoh - 12-26-2015, 11:09 PM
5DMKIII versus 7DMKII - by JJ_SO - 12-27-2015, 12:55 AM
5DMKIII versus 7DMKII - by Ayoh - 12-27-2015, 01:04 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-27-2015, 08:46 AM
5DMKIII versus 7DMKII - by Ayoh - 12-27-2015, 09:51 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-27-2015, 09:59 AM
5DMKIII versus 7DMKII - by davidmanze - 12-31-2015, 09:48 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-31-2015, 10:47 AM
5DMKIII versus 7DMKII - by JJ_SO - 12-31-2015, 02:39 PM

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