2, focusing technology differences: STM lens can complete continuous autofocus, suitable for shooting dynamic video. USM drives the lens by converting ultrasonic vibration into kinetic energy, and achieves high-sensitivity focusing and smooth focusing transition effect.
3. The difference of focusing methods: STM lens adopts an electronically controlled focusing ring, and accurate focusing effect can be obtained when manual focusing is used. USM lens adopts ultrasonic focusing, and the focusing speed is faster.
Detailed explanation of the difference between the two:
1, STM stepping motor, which is the abbreviation of Canon mechanical motor. The focus sound is a little louder than USM sound, especially the focus sound I heard on 50mm F 1.8. I thought there was something wrong with the lens, and the sound would be louder on the fixed focus.
Low-cost STM motors are mostly installed on fixed-focus lenses with various sleeves and small apertures.
2.USM is the abbreviation of Canon ultrasonic motor, which has the advantages of fast focusing speed and relatively small focusing sound! But it's also called local tyrant motor.