Why is the cost nearly double for USM and is it work that cost?

  • In general, ring type USM lenses are the fastest focusing. BUT.... There are now 4 different types of Canon USM lenses. Each type of USM has different operating characteristics. In order to answer your question we need to know which 2 lenses you are comparing. There are very few examples of Canon lenses that are available in both STM and USM versions. The only ones I can think of are the 18-135 STM/18-135 Nano USM and the 24-105 STM/24-105 USM. – Mike Sowsun Feb 25 '18 at 19:10
  • @MikeSowsun The two 24-105 lenses aren't equivalent; the STM is consumer grade f/3.5-5.6, the USM is L grade fixed f/4. – Philip Kendall Feb 25 '18 at 21:21
  • Good point, so really the only Canon lens that has both STM and USM versions is the 18-135. – Mike Sowsun Feb 26 '18 at 2:43
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    "Why is the cost nearly double..." The cost of what? Which two lenses are you comparing? – Michael C Feb 26 '18 at 6:38
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    Possible duplicate of Why do higher end lenses use USM instead of STM? – inkista Feb 26 '18 at 21:28

To sum it up: USM is fast and STM is smooth.

In the question, you're asking what is best for wildlife and sports so USM would be the best for you.

Why? USM focus designs are designed to be quick first while also keeping as quiet as possible. They're generally what is used with L series lenses (Canons professional lens range). As for STM, these aren't as fast as USM, however, they're generally quieter and smoother.

If your goal is to take photos of quick subjects then USM is the best option. However, as you pointed out these also tend to be more expensive but they also offer the fastest focus.

This video shows off the noise vs speed of both STM and USM

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