計算攝影長曝光手機攝影

摘要

長曝光攝影產生令人驚艷的影像，展現場景中移動元素的運動模糊。通常有兩種模式，分別產生前景或背景的模糊效果。傳統上，前景模糊影像是在三腳架上固定的相機上拍攝，呈現模糊的移動前景元素，如絲滑水流或光線軌跡，背景景觀則完全清晰。背景模糊影像，也稱為追焦攝影，是在相機追蹤移動主題的同時拍攝，以產生一張主題清晰的影像，背景則因相對運動而模糊。這兩種技術都極具挑戰性，需要額外的設備和高級技能。在本文中，我們描述了一個計算爆發攝影系統，運行於手持智慧型手機相機應用程式中，並能在按下快門按鈕時完全自動實現這些效果。我們的方法首先檢測並分割突出的主題。我們跟踪多幀的場景運動並對圖像進行對齊，以保留所需的清晰度並產生美觀的運動軌跡。我們拍攝一系列曝光不足的照片，並選擇能產生控制長度的模糊軌跡的輸入幀子集，無論場景或相機運動速度如何。我們預測幀間運動並合成運動模糊，以填補輸入幀之間的時間差。最後，我們將模糊影像與清晰的常規曝光合成，以保護臉部或幾乎不動的場景區域的清晰度，並生成最終高分辨率和高動態範圍（HDR）照片。我們的系統使之前僅供專業人士使用的功能普及化，使這種創意風格對大多數休閒攝影師都可達到。更多信息和補充材料可在我們的項目網頁上找到：https://motion-mode.github.io/

English

Long exposure photography produces stunning imagery, representing moving elements in a scene with motion-blur. It is generally employed in two modalities, producing either a foreground or a background blur effect. Foreground blur images are traditionally captured on a tripod-mounted camera and portray blurred moving foreground elements, such as silky water or light trails, over a perfectly sharp background landscape. Background blur images, also called panning photography, are captured while the camera is tracking a moving subject, to produce an image of a sharp subject over a background blurred by relative motion. Both techniques are notoriously challenging and require additional equipment and advanced skills. In this paper, we describe a computational burst photography system that operates in a hand-held smartphone camera app, and achieves these effects fully automatically, at the tap of the shutter button. Our approach first detects and segments the salient subject. We track the scene motion over multiple frames and align the images in order to preserve desired sharpness and to produce aesthetically pleasing motion streaks. We capture an under-exposed burst and select the subset of input frames that will produce blur trails of controlled length, regardless of scene or camera motion velocity. We predict inter-frame motion and synthesize motion-blur to fill the temporal gaps between the input frames. Finally, we composite the blurred image with the sharp regular exposure to protect the sharpness of faces or areas of the scene that are barely moving, and produce a final high resolution and high dynamic range (HDR) photograph. Our system democratizes a capability previously reserved to professionals, and makes this creative style accessible to most casual photographers. More information and supplementary material can be found on our project webpage: https://motion-mode.github.io/

計算攝影長曝光手機攝影

Computational Long Exposure Mobile Photography

摘要

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