曝光時相機的震動是照片模糊的最常見原因 尼康的防手震(或減震VR: Vibration Reduction)可以幫助減少這個問題的發生Camera shake (unintentional movement of a camera during an exposure) is probably the most common cause of pictures being spoilt by a lack of sharpness. Nikon's Vibration Reduction (VR) system helps to reduce the effects of camera shake.
首先必須分清楚 被照主題的移動和相機的移動是不一樣的 前者須要用高速的快門來”凍結”其運動而形成靜止的影像 在這個狀況下 防手震功能是無效的 後者則是相機在曝光時間內不是完全靜止而有移動 在這種狀況下整個畫面都會模糊 這時使用減震功能有可能有幫助 It is important to draw the distinction between subject movement and camera movement (camera shake). The speed of the former will dictate the shutter speed required to arrest that motion and render the subject sharply; VR has no effect on subject movement. However, if the camera moves in relation to the subject during the exposure, regardless of whether the subject is moving or not, there is a risk that some or all of the image may be blurred. It is in these circumstances that VR can be of benefit.
VR 鏡頭中有一些鏡片是裝有角速度感測器的 它們可以偵測到相機的左右及俯仰角度 及速度 當減震功能開啟時 這些感測器不斷地測量並計算機身的微小抖動 然後由一組馬達VCM迅速地推動這組透鏡做反向的移動以為補償 通常僅需要千分之一秒 最終 結果就可是較穩定的影像
另外 減震系統還能判斷像機的移動是否是刻意的 比如說 系統可以分辨攝影者是否在做追跡攝影而大幅度擺動相機 這時系統就僅會去減少俯仰角的震動 而不去理會左右的移動 (譯注:減震系統對大幅度的動作是沒有辦法消除的)
In the case of the panning technique, which involves swinging the camera deliberately to track a moving subject, VR can help by reducing the effect of camera movement in the plane perpendicular to the path of the camera's motion. All Nikon VR lenses are capable of detecting a panning motion and only dampening camera movement in the opposite plane.
The VR Nikkor lens contains a group of elements that have two motion sensors attached to them. Nikon refer to these as 'angular velocity sensors'; one detects "yawing" motion (rotation around a vertical axis), and the other detects "pitching" (rotation around a horizontal axis).
When the VR system is active these sensors detect information concerning lens movement continuously. Using the information calculations are performed instantaneously and based on the results of these the VR lens group is moved by a group of motors, known as Voice-coil motors (VCM), to an appropriate position that counters the effect of any unintentional lens motion.
The VR system continues to monitor lens motion and will adjust the position of the VR lens element group accordingly as soon as it detects any changes in the orientation of the lens. The micro-computer used to process the information from the motion sensors, perform the calculations, and send instructions to the VCMs operates in a faction of a second; typically taking no more than 1ms (1/1000th second) to complete its functions.
Furthermore the VR system is capable of determining whether or not the motion of the lens is likely to be intentional, such as the technique of panning; in this situation only motion in the plane perpendicular to the movement of the lens is corrected. This is achieved by the use of complex algorithms contained in the firmware of the VR lens. These algorithms are based on a large sample of information collected from a wide variety of conditions that induce unintentional camera vibration; the microcomputer uses them to control the poisoning of the VR lens group.