Perceived Facial Distortions in Selfies Are Explained by Viewing Habits
Perceived Facial Distortions in Selfies Are Explained by Viewing Habits
复制标题
自拍中感知到的面部扭曲是通过观看习惯来解释的
DOI：
10.1001/jamafacial.2018.0649
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发表时间：
2018
影响因子：
--
通讯作者：
Banks, M.S.
中科院分区：
文献类型：
--
作者：
Cooper, E.A.;Banks, M.S.
在他们最近的文章中，沃德等人分析了相机距离对照片中面部尺寸相对大小的影响。他们认为，这些维度在“自拍”中被扭曲了--自拍是人们在一臂远的地方用智能手机相机拍摄的照片。鉴于自拍越来越流行，他们对美容医疗程序的这种明智决定表示担忧。我们同意作者对照片中面部尺寸的计算。然而，我们希望澄清自拍时鼻子变宽的原因。鼻子变宽并不像作者所认为的那样是由于照片中的物理变形。当你从不同的距离看一个人的脸时，投射在视网膜上的图像会发生变化，但表面上的三维形状不会发生变化。你的大脑会考虑到与脸部的距离，并相应地解释视网膜图像。当你看那些办公室的时候呢？每张人脸照片都有一个观看距离，照片中的尺寸（如鼻-鼻比例）忠实地再现了观看者从特定距离观看真实的三维人脸时所看到的尺寸。关键是找到正确的观看距离。对于自拍照或其他照片，你应该从远处观看，这样照片中脸部所对的视角就等于照片拍摄时相机位置所对脸部的角度。2对于自拍来说，这个距离要比肖像照片近得多，因为照片是近距离拍摄的。当你从正确的距离观看时，感知到的面部尺寸应该与真实尺寸非常匹配（假设使用了高质量的透镜，就像现代智能手机相机一样）。如果你从错误的距离观看面部照片，会发生什么？当从太近的地方观看时，脸部看起来比实际上更深更平。当从太远的地方看时，脸看起来比实际上更深更圆。3，4重要的是，这些影响不是由照片中的失真引起的，而是由正确和实际观看距离之间的不匹配引起的。读者可以用Ward等人文章中的照片来尝试一下。1自拍的正确距离是非常近的：大约是照片宽度的两倍。另一张照片的正确距离大约是10倍的宽度。如果您从特写镜头中观看这个selfie，它看起来应该不那么扭曲。事实上，研究表明，人们通常从很远的距离观看短焦距的照片，比如自拍。4这就是感知失真的原因，照片中没有任何固有的失真。对照片中感知形状的评估必须考虑到人类的感知和观看习惯，以及照片的物理特性。
To the Editor In their recent article, Ward et al1 analyze the effect of camera distance on the relative sizes of facial dimensions in photographs. They argue that these dimensions are distorted in “selfies”—photographs that people take of themselves with a smartphone camera at arm’s length. Given the increasing popularityofselfies, theyexpressconcernthatsuchphotographsaffect decisions about cosmetic medical procedures. We agree with the authors’ calculations of facial dimensions in photographs. We wish, however, to clarify the cause of perceived nasal widening in selfies. The perceived nasal widening is not, as the authors suggest, due to physical distortion in the photographs. Whenyouseeaperson’sfacefromdifferentdistances, theimage cast on your retinas changes, but the apparent 3-dimensional shape does not. Your brain takes into account the distance to the face and interprets the retinal images accordingly. What about whenyoulookatphotographsoffaces, suchasselfies? Everyphotograph of a face has a viewing distance from which the dimensionsinthephotograph (suchasthenasal-bizygomaticratio) faithfully reproduce the dimensions that the viewer would see when looking at the real 3-dimensional face from a specific distance. The trick is to find the correct viewing distance. With selfies, or any other photograph, you should view from a distance such that the visual angle subtended by the face in the photograph equals theanglethatthefacesubtendedfromthecamera’spositionwhen the photograph was taken. 2 For a selfie, this distance is going to bemuchcloserthanforatypicalportrait, becausethephotograph was captured from close up. When you view from the correct distance, the perceived facial dimensions should closely match the true dimensions (assuming a high-quality lens is used, as in modern smartphone cameras).What happens if you view a photograph of a face from the wrong distance? When viewing from too close, the face appears compressed in depth and flatter than it actually is. When viewing from too far, the face appears stretched in depth and rounder than it is. 3, 4 Importantly, these effects are not caused by distortions in the photographs but by a mismatch between the correct and actual viewing distances. The reader can try this out with the photographs in the article by Ward et al. 1 The correct distance for the selfie is very close: roughly twice the photograph’s width. The correct distance for the other photograph is approximately 10 timesthewidth. Ifyouviewtheselfiefromcloseup, itshouldlook less distorted. Indeed, research suggests that people usually view photographstakenwithshortfocallengths—suchasselfies—from much too great a distance. 4 This is the reason for the perceived distortion, and there is nothing inherently distorted in the photographs. Evaluations of perceived shape in photographs must take into consideration human perception and viewing habits, in addition to the physical properties of photographs.