USM VS STM

在同一BODY及環境設定下
兩者既自動對焦驅動模式 邊種比較快及靜

回覆 1# aaoo.


USM快
STM靜

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本帖最後由 harryytm 於 2015-3-27 01:55 編輯

USM有兩種,Ring USM同Micro USM。
Ring USM扭力大和精確度高,適合快速切換焦點的操作,但未做到完全無聲,而且只有固定運轉速度,做唔到微細的對焦。
Micro USM係用齒輪提高扭力,所以速度和精確度較Ring USM略差。

STM有兩種,Lead Screw 和Gear
Lead Screw STM扭力唔夠Ring USM,唔可以移動太重的鏡片組,但可以做到寧靜、平順和微細的對焦,適合拍片自動對焦,由於可以做到微細的對焦,有利Live View時使用的反差對焦。
Gear STM對焦速度慢,但可以做到好細,適合比餅鏡用。

用DSLR的OVF對焦速度係Ring USM>Lead Screw STM>Micro USM>Gear STM
用Live View時純CDAF速度係Lead Screw STM>Ring USM>Gear STM>Micro USM
Hybrid AF可以降低USM因為做唔到微細的對焦的弱點,縮短對焦時間。

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本帖最後由 PPLd 於 2015-3-27 08:32 編輯
USM有兩種,Ring USM同Micro USM。
Ring USM扭力大和精確度高,適合快速切換焦點的操作,但未做到完全無聲 ...
harryytm 發表於 2015-3-27 01:53


My 300/2.8 IS has fixed AF drive speed. It would vibrate if u are tracking slow objects.
However, the movie focus ring of my 300/2.8 IS II have slow and fast mode.
I hv nvr tried it though so not sure what they mean!

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USM有兩種,Ring USM同Micro USM。
Ring USM扭力大和精確度高,適合快速切換焦點的操作,但未做到完全無聲 ...
harryytm 發表於 27-3-2015 01:53


N記用家一問, STM有無需要機身特別支援?
定係是但一部EOS都用到?

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本帖最後由 harryytm 於 2015-3-27 10:03 編輯
N記用家一問, STM有無需要機身特別支援?
定係是但一部EOS都用到?
raisin 發表於 2015-3-27 09:40

試過EOS菲林機都用到。機身如果有Hybrid CMOS AF,LiveView對焦可以快啲,DualPixel CMOS AF就可以LiveView對焦做到接近OVF既對焦速度。

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試過EOS菲林機都用到。
harryytm 發表於 27-3-2015 10:00


效果同 70D用STM一樣? 因為所有野都係鏡身做晒嗎?

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效果同 70D用STM一樣? 因為所有野都係鏡身做晒嗎?
raisin 發表於 2015-3-27 10:02

70D有DualPixel CMOS AF,配合STM鏡LiveView的對焦速度可以做到接近用OVF,但如果唔會用LiveView影相基本上對焦速度同其他鏡差不遠。

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70D有DualPixel CMOS AF,配合STM鏡LiveView的對焦速度可以做到接近用OVF,但如果唔會用LiveView影相基本 ...
harryytm 發表於 27-3-2015 10:16


明白... thx

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本帖最後由 harryytm 於 2015-3-27 10:56 編輯

我發現其實STM鏡仲有一個隱藏功能,就係Zoom的時候有對焦距離補償修正,點Zoom都係Keep仲同一個對焦距離,我無USM的Zoom鏡試唔到USM鏡有無這個功能,以及唔知係唔係STM鏡獨有。
The first I've seen it in any lens for still photography, the focus is compensated electronically as the lens is zoomed. If the camera's meter isn't on, the lens goes completely out of focus as you try to zoom. So long as the camera is on and awake it stays in focus as you zoom, but if it's off, it will only be in focus at one focal length setting. This isn't related to the autofocus system, it's part of the basic design of the lens. More at Usage.
Source: http://www.kenrockwell.com/canon/lenses/18-55mm-stm.htm#spex
Focus is continuously compensated as you zoom, and the camera has to be ON for this to happen.

If you zoom the lens with the camera OFF or asleep, focus won't hold as you zoom. If the camera is awake, focus holds as zoomed because the advanced electronic programs are compensating focus electronically as you turn the mechanical zoom ring.
Source: http://www.kenrockwell.com/canon/lenses/55-250mm-stm.htm#focus

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