shutter困难

A butterfly takes off so quickly it is still impossible to react quickly enough to capture that take-off but if he half-presses the shutter, the camera saves the 70 previous frames before the moment he actually takes the picture.

蝴蝶起飞得太快，人仍然不可能反应快到捕捉到起飞的那一刻，但如果他半按快门，相机就会保存他真正按下快门之前的70帧画面。

That makes it sound easy, and artificial, but Peters insists it is still a massive challenge. He typically takes between 10,000 and 20,000 shots to get one butterfly take-off sequence in focus. At such high shutter speeds, the depth of field is tiny, and as butterflies do not fly in a straight line they swiftly flutter out of focus. As well as thousands of attempts, it takes patience and fieldcraft to anticipate a butterfly’s likely flight-line — and catch it — in focus.

这听起来既简单又人为，但彼得斯坚称这仍是一项巨大的挑战。他通常要拍一万到两万张照片，才能得到一组对焦清晰的蝴蝶起飞序列。在如此高的快门速度下，景深非常小，而且蝴蝶并不沿直线飞行，很快就会扑腾着飞出焦点。除了成千上万次的尝试，还需要耐心和野外经验来预判蝴蝶可能的飞行路线——并在焦点内捕捉到它。