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I have been looking at the Nikon AF-S 35mm f1.8 lens and it has two focus settings:

  • Manual Focus
  • Manual-Priority Autofocus

What is "manual-priority autofocus"?

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    The answers you already got are correct. There are many names for this depending on the camera or lens manufacturer: DMF (Direct Manual Focus), AF+MF, Full-Time Manual Focus (Lens) and Quick-shift Autofocus are the ones I remember early Sunday morning :) – Itai Jan 23 '11 at 16:53
  • I had the lens for a few days and loved this feature. It let me use the camera's brain to auto focus fast then dial it in by hand when taking pictures at close range where the auto focus seemed to have trouble getting a lock. – kacalapy Jan 23 '11 at 18:06
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Manual-priority allows the lens to auto focus but still allows you to adjust the focus manually. Many other lenses lock the focus ring when using auto focus to prevent damage to the internal motor. This lens is designed to allow full time manual override which is very useful to tweak focus without switching out of auto mode.

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  • Great stuff - thanks for this answer. Sounds like I can point the camera at a person, let it autofocus and then tune in the focus to get the eyes really sharp! – Fenton Jan 24 '11 at 9:13
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If it's like Pentax's fulltime manual in autofocus then it's basically autofocus mode with the ability to manually adjust the result without switching out of autofocus. If you have a lens without this, then manual adjustments are bad for the lens when the body is set to autofocus and so you need to switch out of autofocus mode to adjust.

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Manual-priority autofocus is a special mode on certain lenses which allows you to stop AF while the lens is still focusing and immediately switch to manual focus.

On most lenses with manual-focus override, while you can adjust the focus manually in AF mode, you can't do this while the lens is in the midst of autofocusing. The manual-priority mode allows you to stop AF right away and manually focus, rather than have to wait until focusing is complete.

On Nikon lenses, this is designated by the M/A position on the autofocus switch. A few professional-grade Pentax lenses have a QFS/M position on the AF switch which does the same.

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    Not really interested in defining 'professional grade' but a number of modestly priced Pentax lenses allow full time manual focus override. Often there are 'kit lens' versions with similar optics and specs that do not allow full time manual focus, e.g. DA 50-200mm f/4-5.6 ED WR comes with manual focus override at ~$200USD if bought separately but the 'kit' version does not. The DA 18-55mm f3.5-5.6 AL WR is similar. – user50888 Feb 10 '17 at 22:24
  • Read the answer carefully. Most lenses do not let you manually focus while the lens is in the middle of AF. Manual-priority autofocus lets you do this. The only lens I have with this feature is the Pentax D FA* 70-200mm f/2.8. – bwDraco Feb 10 '17 at 22:27

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