3D 影像之立體感與舒適度探討

Abstract

3D電影在近幾年開始受歡迎與流行，也導致一種新的症狀產生，稱做3D不適症或是阿凡達暈眩症。目前解釋的說法多偏重設備硬體的缺失，或是觀者生理層面的差異；卻較少討論到影像本身，是否因為3D影像製作過程的問題，才誘發人類視覺與大腦的不適。本研究有二部分假設：一是誇大眼睛網膜像差或是忽略人眼肌肉運動時，可能會產生不適；二是傳統平面影像的攝影技巧與美學，完全移植到3D立體影像而不修正時，可能也會造成不適。研究在這假設底下規劃了四個實驗：(1)像差距離實驗；(2)聚合對焦實驗；(3)焦距與景深實驗；(4)亮度與景深實驗。 研究結果發現：(1)像差距離是眼睛不適的主因；(2)最佳立體效果與最佳舒適度無法兼顧；(3)輻輳運動可有效提高視覺舒適度；(4)攝影焦距數值與景深模糊範圍成正比；(5)環境亮度下降，景深模糊範圍寬容度則會增加；(6)景深對視覺舒適度無影響。 本研究所量測出的舒適區間與立體效果區間之參數範圍，可以供3D材料製作者參考，以在立體感與舒適度之間取得最佳平衡。

As technology advances, 3D movies enjoy a tremendous boost in recent years. With its popularity, a new symptom of 3Dache or Avatarh3dache emerges as well. Most studies addressing this issue placed their emphasis on finding plausible solutions at the display end. This study takes a new perspective by focusing on the production end for solving the problem. Two groups of possible causes are proposed and will be thoroughly examined. First, exaggerating the retinal disparity or ignoring the oculomotor cues may cause visual discomfort. These factors are related to the geometry of camera-setup. The second group pertains to visual effects of assorted kinds. Visual discomforts might be induced by applying traditional 2D photographic techniques to 3D situations blindly. Four experiments are designed to evaluate the effects of these factors: (1) Inter-camera distance; (2) vergence angle of the camera; (3) Focal length and depth of field; (4) Lightness and depth of field. Our results indicate that: (1) Unnatural disparity is the main cause of eye discomfort; (2) There is some trade-off between three-dimensional effects and visual comfort. These two parameters cannot be optimized simultaneously; (3) Convergence can improve visual comfort; (4) The degree of depth of field in a 3D shooting should be set according to the focal length of the lens; (5) As the ambient brightness decreases, one should reduce the depth of field accordingly to achieve good visual effect; (6) Depth of field has no effect on visual comfort.