In addition to auto focusing, modern lenses allow photographer to decide what subject should be focused on. Full-Time Manual Focusing allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don’t have to switch camera and/or lens to manual focus mode.
|Canon||Full-Time Manual Focusing||Manual focus adjustments at any time after the camera has locked the focus automatically|
|Nikon||A/M||Autofocus mode priority with switching to manual focus mode after some delay. Used to prevent accidental switching to manual focus mode|
|Nikon||M/A||Instant switching from autofocus to manual focus mode, even in continuous AF mode|
|Pentax||Quick-Shift Focus System||Manual focus adjustments at any time after the camera has locked the focus automatically|
|Samsung||Direct Manual Focus||Manual focus adjustments at any time after the camera has locked the focus automatically. The function is provided by the camera|
|Sigma||Full Time Manual Focusing||Manual focus adjustments at any time after the camera has locked the focus automatically|
|Sigma||Manual Override||Instant switching from autofocus to manual focus mode, even in continuous AF mode|
|Sony||Direct Manual Focus||Manual focus adjustments at any time after the camera has locked the focus automatically. The function is provided by the camera|
|Tamron||Full Time Manual Focus||Manual focus adjustments at any time after the camera has locked the focus automatically|
|Tokina||One Touch Focus Clutch||The switching of manual focusing ring towards the mount puts lens in manual focus mode. The return to autofocus mode is performed by switching the ring backwards|
Full-Time Manual Focusing is available with ring-type ultrasonic motors. This is true for almost all photographic lenses except for those made by Pentax Corporation — the company equipped most of its modern lenses with Quick-Shift Focus System (even those which do not have any AF motor or equipped with conventional micromotor). Tokina’s One Touch Focus Clutch technology is also supported despite the type of lens AF motor.
In case of Canon EF/EF-S lenses the only exception is Canon EF 50mm F/1.4 USM which has Micro USM but also SUPPORTS this function thanks to a special gear. Moreover, the early version of Full-Time Manual Focusing used in Canon EF 85mm F/1.2L USM, Canon EF 50mm F/1L USM and several older models was based on focus-by-wire principle — the photographer had to half-press and hold the shutter button during the focusing and the manual focusing was actually performed by the AF motor. Such principle is nowdays used in Canon EF/EF-S lenses equipped with stepping AF motors. As for the rest of Canon lenses with ring-type ultrasonic motors, they have mechanical implementation of Full-Time Manual Focusing which ensures fast response.
In the Minolta/Sony A system the Direct Manual Focus is provided by the camera itself. Konica Minolta, Minolta, Sony, ZEISS lenses which rely on in-camera motor or have ultrasonic motor are compatible with Direct Manual Focus. Konica Minolta, Minolta and Sony lenses which have 1st generation micromotor are not compatible with Direct Manual Focus. Sony DT 18-55mm F/3.5-5.6 SAM II (SAL18552) equipped with 2nd generation micromotor is COMPATIBLE with Direct Manual Focus. Sony DT 18-135mm F/3.5-5.6 SAM (SAL18135) is another exception because its 1st generation micromotor SUPPORTS Direct Manual Focus thanks to a special gear.
The manual focusing ring is blocked or does not result in focus change in AF mode with lenses which do not support Full-Time Manual Focusing. With some older lenses the ring rotates automatically during AF and the AF motor could be damaged if you will try to perform manual focusing at that moment.