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Because! the! focu sing ! element! (“focus! lens”! in! Figure ! 24! above)! is ! small! and! lightweight!the! focusing!
actuator! deploys! a! Nano! USM! (ne w ! Thin -type).! ! This! motor! uses! the! basic! Ultrasonic! principle,! of!
extremely!controlled,!fine! vibrations! produced!by!running! current!through!a! specific!metal!device.!!In!
this!case,!the!"device"!looks!almost !like!a!t in y!meta l!banda g e,!with !little!project in g !nubs!on!either!side!
—! Figure! 26.! ! These! in ! turn! co ntact! a! sliding! surface,! and! vibrations! are! transformed! into! linear!
movement,! and! a! lens! element! guided! by! a! control! bar! moves! fore! or! aft! to! drive! fo cu s! in! either!
direction.!!&&&
&&&&&& !
Figure &2 6! !!!!Showing$the$Nano$ USM $ used$ to$ actuate$ the$focusing$ element$ in$ the$ new$ RF24-105mm $
F4$L$IS$USM$zoom$lens$
The!Nano!USM!is!very!quick!an d!quiet!and!is!particularly!well-suited!to!stop-and-start!operation!that's!
quite!common!in!video!shooting.!!It!also!helps!ensure!much!smoother!AF!during!video!acquisition.&
&
11.3.1&&&&&&&&&&&&&&&&&&MTF&Characteristics&of&the&RF24-105mm&F4&L&IS&USM&Zoom&Lens&
&&&&&
Figure&27$$$$$$$MTF$characteristics$of$the$RF24-105mm$F4$L$IS$U SM$$le n s$a t$b o th $t he $wide$end$and $th e $
telephoto$end &
24!
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