Talk about the motors in cameras and lenses

When it comes to motors in cameras and lenses, I believe the first thing that comes to mind is the focus motor of the autofocus lens.

In the early days, some brands chose the body drive solution, but now most brands choose the more efficient lens built-in motor. (PENTAX has also begun to equip new lenses with focus motors in recent years)

▲ Minolta AF7000 is an AF SLR camera that uses a body-driven solution (the red circle is the drive gear)

DC motors and their derivatives have basically withdrawn from the mainstream vision. The main focus motors currently used are STM stepping motors, ultrasonic motors, and new high-performance motors represented by XD/VXD/SSVCM.

▲ DC motor used in early low-end lenses

STM stepper motors have two drive structures: gear type and lead screw type:

- The gear type is slower and has a louder working noise. If you have a bad impression of "STM", then you are most likely to have encountered an STM gear drive structure.

- The lead screw type allows the focusing lens to move linearly, making focusing smoother and faster. It is a good choice that takes both cost and focusing performance into consideration.

▲ STM + lead screw (left) and STM + gear (right)

Ultrasonic motors have been a must-have feature of high-spec lenses for a long time since they were first introduced in 1987. There are three common types of ultrasonic motors:

- Ring-shaped ultrasonic motors have considerable torque and are suitable for driving large aperture fixed focal length lenses and relatively bulky focusing lenses of telephoto/super telephoto lenses. They are relatively simple in structure and reliable, but their response speed is not as fast as that of linear motors or stepping motors.

▲ Ring ultrasonic motor

- Micro ultrasonic motors are small, light, and low cost. (But Nikon seems a bit "stingy" when using micro ultrasonic motors on some gold-rimmed lenses)

- Canon NANO USM and Sony DDSSM are both linear-driven ultrasonic motors. They have no transmission structure and are very quiet, making them suitable for CMOS AF and video shooting. However, their driving force is not as good as that of a ring-shaped ultrasonic motor, so the focus lens group they are paired with is also relatively lightweight.

* When the linear focus motor is not powered, the focus lens may shift. That is, if you shake the lens, you can feel the lens inside sliding. This is normal.

▲ Canon NANO USM

The new high-performance motors mainly refer to Sony XD, Tamron VXD and Nikon SSVCM. These three are high-performance focus motors born in the era of micro-single cameras, and all are linear focus. Sony's official information is relatively limited and the names are relatively abstract, while Tamron and Nikon have more specific structures and schematics. I personally tend to think that these three are similar technologies, and I look forward to a more in-depth interpretation from a big shot.

▲ Sony XD motor

▲ Tamron VXD motor

▲ Nikon SSVCM motor

Judging from the official disassembly pictures, the XD motors and focus lens groups of some Sony lenses use non-metallic brackets (the situation is similar for Tamron, and the Nikon Z 400/2.8 VR S and Z 600/4 VR S have not yet been disassembled), which may not be as reliable as traditional ring-shaped ultrasonic motors when encountering bumps and collisions.

▲ Sony FE 50mm F1.2 GM lens's XD motor and focus lens assembly

Finally, motors are not only used for lens autofocus, but can also be used for aperture blade control, electric zoom and sensor shift image stabilization: Canon's early DC products used ultrasonic motors to drive zoom, and Sony also used ring ultrasonic and XD motors to drive lens zoom.

▲ Sony FE PZ 16-35mm F4 G's XD motors are used for electric zoom and focus respectively

▲ Canon uses USM ultrasonic motor for zoom digital camera