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What Does STM Mean On A Canon Lens?

STM stands for Stepping Motor and it is one of Canon’s autofocus motor technologies that they use in lenses. 

One of the most popular Canon STM lenses is the 50mm f1.8 STM.

STM lenses allow for quieter and smoother focusing which is particularly useful for video recording as you don’t want any distracting noises. An alternative type of autofocus motor that Canon uses is their USM motor.

What Does USM Mean on a Canon Lens?

USM stands for UltraSonic Motor on Canon lenses.

If you are only taking photos rather than videos, then having an STM lens probably will not make much difference to you and therefore you might not care much about it. USM lenses are not as quiet as STM lenses when auto focusing so you may want to avoid USM lenses if you plan to only shoot video with autofocus.

An example of a popular Canon USM lens is the Canon EF 50mm F/1.4 USM.

What Is the Difference Between STM and USM Lenses?

USM lenses are louder than STM lenses and you can hear the noise in your recordings. However, USM lenses are also generally faster to focus compared to STM lenses. 

STM lenses may be slightly slower to autofocus, but they are much smoother. 

If you are someone who is solely shooting video with the use of autofocus then STM lenses can be beneficial.

On the other hand, if you are just shooting for photos then the quietness of the autofocus probably has no impact on your shot. In this case, there isn’t any obvious advantage to using an STM lens. 

So Should All Videographers Use STM Lenses? 

While STM lenses are quieter when auto focusing there won’t really be an advantage when using manual focus.

A lot of videographers will shoot solely with the use of manual focus so that they can have full control of the shot. In this case, there wouldn’t be any real benefit in using an STM lens over a USM lens. 

STM VS USM Sound Comparison

The video below does a good job of showing you the sound differences between the two autofocus motors. You can clearly hear the USM being more noticeable.

Should I Buy An STM lens?

If you are a videographer who relies on autofocus a lot and you will be using sound from the in camera recordings then STM can be very good. It’s also great for smooth autofocus which is useful when recording.

Watch the video below for a overview of STM lenses, explained by Canon themselves.

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