{"slug":"correct-exposure-digital","title":"《纽摄》早已过时，数码时代如何正确曝光","author":"Thomas看看世界","date":"2016-10-30","wechat":"https://mp.weixin.qq.com/s?__biz=MzI4NDA5MzE5NQ==&mid=2247484523&idx=1&sn=96164523b44ae083590b0dc23ee19068&chksm=eb81fa0fdcf6731949a5cd7d48d1ee27a2372432455ed7236a576b188a9a6fcf5833dbfb4723&scene=21#wechat_redirect","blocks":[{"t":"p","x":"传统摄影教材，如《纽约摄影学院教程》中，对正确曝光的定义都是基于“18%灰”和复杂的测光表系统。","b":false,"xe":"Traditional photography textbooks, such as the New York Institute of Photography course, define correct exposure based on '18% gray' and complex light-meter systems."},{"t":"p","x":"在相机硬件和后期技术突飞猛进的今天，这套曝光理论的可操作性已经大大降低，而且很多时候并不是最佳方案。数码时代如何正确曝光？为什么“宁欠勿过”和“向右曝光”同时成立？是我们今天要探讨的话题。","b":false,"xe":"With today's rapid advances in camera hardware and post-processing, that exposure theory is far less practical — and often not the best approach. How should we expose in the digital age? Why can 'underexpose rather than over' and 'expose to the right' both be true? That's today's topic."},{"t":"p","x":"知识点：直方图、动态范围、宽容度、包围曝光、数码欠曝、数码过曝、向右曝光、宁欠勿过","b":false,"xe":"Key concepts: histogram, dynamic range, exposure latitude, exposure bracketing, digital underexposure, digital overexposure, expose to the right, underexpose rather than over"},{"t":"h","x":"1","xe":"1"},{"t":"h","x":"传统曝光理论的局限性","xe":"The Limits of Traditional Exposure Theory"},{"t":"p","x":"传统的曝光理论，要求摄影师用测光系统，对场景中的特定区域进行测光，保证18%反射率的灰色物体、或者场景中重要的区域（如人脸），其亮度在照片中得到真实还原。","b":false,"xe":"Traditional exposure theory asks the photographer to meter specific areas of the scene, ensuring that an 18%-reflectance gray object — or an important area like a face — is rendered at its true brightness in the photo."},{"t":"p","x":"这套曝光理论，强调照片亮度的真实性和准确性，在这个时代已经有点过时，原因如下：","b":false,"xe":"This theory, which emphasizes faithful and accurate brightness, is somewhat outdated today, for the following reasons:"},{"t":"p","x":"1）相机芯片技术、Raw格式数字底片技术、以及后期技术的不断发展，使得前期曝光并不准确的照片，后期也能轻松的还原。在这基础上，还发展出了“宁欠勿过”和“向右曝光”两套理论，分别提出要在拍摄时适当欠曝或者过曝。（关于这两个相反的说法，后面托马斯还会详细阐述，不过他们有一个共同点，都是不让你准确的曝光。。。）","b":false,"xe":"1) Advances in sensor technology, RAW digital negatives and post-processing mean inaccurately exposed frames can be easily corrected afterward. On this basis, two opposing schools emerged — 'underexpose rather than over' and 'expose to the right' — advocating deliberate under- or overexposure. (Thomas will explain these contradictory claims in detail later; they share one trait: neither wants you to expose 'accurately'…)"},{"t":"p","x":"2）包围曝光、HDR、亮度蒙版等技术的发展，使得越来越多的人使用多张拍摄，每张照片对场景不同区域曝光再后期合成的方法。","b":false,"xe":"2) The rise of exposure bracketing, HDR and luminosity masks means more and more people shoot multiple frames — each exposed for a different part of the scene — and blend them in post."},{"t":"p","x":"3）人们不再简单的想还原场景的真实曝光，而更多的想通过个性化的亮度调整，让照片反映出不同的影调、情绪和艺术效果。","b":false,"xe":"3) People no longer simply want to reproduce a scene's true exposure; they want personalized brightness adjustments that give photos different tones, moods and artistic effects."},{"t":"h","x":"所以数码时代，我们不再需要曝光准确，而只需要最大化的记录下场景中的光线信息。","xe":"So in the digital age, we no longer need 'accurate' exposure — we only need to record the maximum amount of light information from the scene."},{"t":"img","f":"img-01","w":700,"h":465},{"t":"h","x":"2","xe":"2"},{"t":"h","x":"数码时代什么是曝光正确","xe":"What Is Correct Exposure in the Digital Age"},{"t":"p","x":"这里托马斯先提出3个定义，为了和传统理论区别，我在前面分别加上了“数码”两个字。","b":false,"xe":"Thomas proposes three definitions here, each prefixed with 'digital' to distinguish them from traditional theory."},{"t":"p","x":"数码曝光正确：当我们在一张或者多张数字底片中，记录下了肉眼所观察到的全部亮度信息，我们就称为数码曝光正确。","b":true,"xe":"Digital correct exposure: when one or more digital negatives record ALL the brightness information visible to the naked eye in a scene, we call it digitally correct exposure."},{"t":"p","x":"数码欠曝：当我们在一张或者多张数字底片中，由于曝光量不足，导致成片暗部细节丢失无法恢复，我们就称为数码欠曝。","b":false,"xe":"Digital underexposure: when insufficient exposure causes shadow detail in the final image to be lost beyond recovery, we call it digital underexposure."},{"t":"p","x":"数码过曝：当我们在一张或者多张数字底片中，由于曝光量过大，导致成片亮部一片白色没有细节，我们就称为数码过曝。","b":false,"xe":"Digital overexposure: when excessive exposure causes the highlights to blow out to detail-less white, we call it digital overexposure."},{"t":"h","x":"总而言之，数码曝光理论，强调的是对场景亮度信息的尽可能记录，而不是准确还原。","xe":"In short, digital exposure theory emphasizes recording as much of the scene's brightness information as possible — not reproducing it accurately."},{"t":"p","x":"只要你在底片中记录下了这些光线信息，即使直接看起来有点过亮或者过暗，但都可以通过后期调整的方式，恢复到准确的亮度。","b":false,"xe":"As long as the light information is recorded in your negative, even if the frame looks too bright or too dark at first, post-processing can restore it to accurate brightness."},{"t":"p","x":"只要信息被记录下来，你就可以通过后期来加深减淡，甚至丢掉某些不需要的信息和细节，达到我们想要的艺术效果。而如果信息没有被记录下来，我们后期也无力回天了。","b":false,"xe":"Once information is recorded, you can dodge and burn in post — even discard unneeded information and detail — to achieve the artistic effect you want. But if information was never recorded, no amount of post can bring it back."},{"t":"p","x":"传统的曝光准确，不一定能记录下来所有的细节和信息。而记录下场景中的所有可见亮度信息，在后期一定可以实现亮度准确还原。所以“数码曝光正确”比传统的曝光准确，有更大的应用空间。","b":false,"xe":"Traditionally 'accurate' exposure may fail to record all detail and information; whereas recording all visible brightness information guarantees accurate brightness can be restored in post. So 'digital correct exposure' has a far wider application than traditional accuracy."},{"t":"h","x":"3","xe":"3"},{"t":"h","x":"数码时代如何正确曝光","xe":"How to Expose Correctly in the Digital Age"},{"t":"p","x":"如何保证场景暗部和亮部的信息都被完整的记录下来呢？当然你可以通过肉眼观察的方法，如果照片亮部不是死白一片毫无细节，照片暗部也不是一片漆黑，那么这张照片应该是“数码曝光正确”的。","b":false,"xe":"How do you ensure shadow and highlight information are both fully recorded? You can judge by eye: if the highlights aren't a featureless dead white and the shadows aren't pitch black, the photo is probably 'digitally correctly exposed'."},{"t":"p","x":"不过相机照片预览、后期软件、甚至某些相机的实时取景预览中，还有一个工具，可以帮助我们进行更科学准确的判断，那就是直方图（Histogram）。","b":false,"xe":"But there's a tool in your camera's playback, in post software, and even in some cameras' live view that enables a more scientific judgment: the histogram."},{"t":"h","x":"3.1","xe":"3.1"},{"t":"h","x":"直方图","xe":"The Histogram"},{"t":"p","x":"人们把照片的亮度分为0到255共256个数值，其中0代表纯黑色的最暗区域，255表示最亮的纯白色，而中间的数字就是不同亮度的灰色。","b":false,"xe":"Brightness is divided into 256 values from 0 to 255, where 0 is pure black, 255 is pure white, and the numbers in between are grays of different brightness."},{"t":"p","x":"当我们用横轴代表0-255的亮度数值，竖轴代表照片中对应亮度的像素数量，这个函数图像就被称为亮度直方图。","b":false,"xe":"Plot the 0-255 brightness values on the horizontal axis and the pixel count at each brightness on the vertical axis — that graph is the luminance histogram."},{"t":"img","f":"img-02","w":700,"h":376},{"t":"p","x":"对JPEG文件格式而言，直方图就代表了照片上记录的所有亮度信息。如果直方图两端有大量像素堆积，也就意味着照片中有大量死白或者死黑，许多细节信息丢失了。","b":false,"xe":"For a JPEG file, the histogram represents all the brightness information recorded in the photo. Large piles of pixels at either end mean large areas of dead white or dead black — much detail is lost."},{"t":"p","x":"对Raw文件格式而言，其记录下的信息范围比直方图表现的更广。直方图上有些显示溢出的高光和阴影细节，也是可以通过后期给拉回来的。但是能拉回来多少，跟环境的光比和相机芯片的能力有关，是个有点“看运气”的东西，所以并不作推荐。","b":false,"xe":"A RAW file records a wider range than the histogram shows: some highlights and shadows that appear clipped can be pulled back in post. But how much can be recovered depends on the scene's contrast and the sensor's ability — somewhat a matter of luck — so I don't recommend relying on it."},{"t":"p","x":"这样我们通过直方图，又可以重新描述我们的上面的三个定义。","b":false,"xe":"With the histogram, we can restate our three definitions."},{"t":"p","x":"数码曝光正确：当照片的直方图两端没有被切断的情况下，场景中的信息就被全部记录了下来，我们可以称这张照片“数码曝光正确”。","b":false,"xe":"Digital correct exposure: when neither end of the photo's histogram is cut off, all the scene's information has been recorded — the photo is 'digitally correctly exposed'."},{"t":"p","x":"所以下面两张都是“数码曝光正确”的照片。","b":false,"xe":"So both photos below are 'digitally correctly exposed'."},{"t":"img","f":"img-03","w":700,"h":440},{"t":"img","f":"img-04","w":700,"h":456},{"t":"p","x":"当然，现代“向右曝光”理论（ Exposure to the right），确认了相机在摄入光线越多的情况下，可以获得更多的细节和更少的噪点。所以第二张直方图是比第一张更好的，第二张后期压暗后可以比第一张得到更少的噪点。但是务必注意，向右曝光的前提是不“数码过曝”。","b":false,"xe":"Of course, modern 'expose to the right' (ETTR) theory confirms that the more light the camera captures, the more detail and less noise you get. So the second histogram is better than the first: darkened in post, it yields less noise. But note — ETTR's precondition is avoiding 'digital overexposure'."},{"t":"p","x":"数码过曝：由于曝光量过大，导致成片亮部一片白色无法恢复，表现为直方图右侧大量像素堆积，像切断了一样，我们就称为数码过曝。","b":false,"xe":"Digital overexposure: excessive exposure blows the highlights to unrecoverable white, shown as a large pile of pixels cut off at the histogram's right edge — that's digital overexposure."},{"t":"img","f":"img-05","w":700,"h":421},{"t":"p","x":"同样的，数码欠曝光在直方图上，表现就是左侧被大量像素切断。","b":false,"xe":"Likewise, digital underexposure shows as a large pile of pixels cut off at the histogram's left edge."},{"t":"img","f":"img-06","w":700,"h":467},{"t":"h","x":"3.2","xe":"3.2"},{"t":"h","x":"大光比环境和宁欠勿过","xe":"High-Contrast Scenes and 'Underexpose Rather Than Over'"},{"t":"p","x":"上面讨论的时候，我们都假设照片要么欠曝，要么过曝。但现实中还有一些情况，比如逆光拍摄，由于光比过大，有可能照片会同时欠曝和过曝。","b":false,"xe":"So far we've assumed a photo is either under- or overexposed. But in reality — for example when shooting against the light — the contrast can be so great that a photo is simultaneously underexposed AND overexposed."},{"t":"p","x":"这是因为自然界中的最亮光线和最暗光线，他们的亮度比值非常的大（这个比值的对数，我们称为动态范围 Dynamic range 或者光比）。","b":false,"xe":"That's because the ratio between the brightest and darkest light in nature can be enormous (the logarithm of this ratio is called dynamic range, or simply contrast ratio)."},{"t":"p","x":"而相机能记录的最亮光线和最暗光线的差别，是在一定范围之内的。相机能记录的最亮光线和最暗光线亮度的比值，我们称为宽容度 (Exposure latitude)。","b":false,"xe":"The range between the brightest and darkest light a camera can record is limited. The ratio of brightest to darkest brightness a camera can capture is called exposure latitude."},{"t":"p","x":"当环境的光比大于相机宽容度时，我们就称这种环境是大光比环境。大光比环境相机无法单张完成“数码正确曝光”，在曝光适中的情况下，直方图左右两侧依然都会被切断。","b":false,"xe":"When the scene's contrast exceeds the camera's latitude, we call it a high-contrast scene. A single frame cannot achieve 'digital correct exposure' there: even at a middling exposure, both ends of the histogram get clipped."},{"t":"p","x":"前面我们说过，raw格式底片能记录的范围是比直方图显示的更大的。现代数码相机，对直方图中切断溢出的阴影部分，其记录还原能力，比直方图中切断溢出的高光部分更强（在索尼和尼康的型号中表现尤其突出）。","b":false,"xe":"As mentioned, RAW negatives record a wider range than the histogram shows. Modern digital cameras recover clipped shadows far better than clipped highlights (especially Sony and Nikon bodies)."},{"t":"p","x":"因此有人提出了“宁欠勿过”的理论：在大光比环境下，宁愿照片数码欠曝、直方图左侧溢出，也不要数码过曝、让直方图右侧大量溢出。这样后期时能恢复的细节会更多。","b":false,"xe":"Hence the 'underexpose rather than over' school: in high-contrast scenes, prefer digital underexposure with the histogram's left edge overflowing, over digital overexposure with the right edge massively clipped — more detail can be recovered in post."},{"t":"p","x":"请注意黑体强化部分，无论是“向右曝光”，还是“宁欠勿过”，都有各自的前提：","b":false,"xe":"Note the bolded parts: both 'expose to the right' and 'underexpose rather than over' have their own preconditions:"},{"t":"h","x":"正常光比环境尽量“向右曝光”，大光比环境“宁欠勿过”。","xe":"In normal-contrast scenes, expose to the right; in high-contrast scenes, underexpose rather than over."},{"t":"h","x":"3.3","xe":"3.3"},{"t":"h","x":"大光比环境的最佳解决方案","xe":"The Best Solution for High-Contrast Scenes"},{"t":"p","x":"虽然利用相机暗部宽容度，来“宁欠勿过”可以一定程度的解决大光比问题，但这并不是画质最好的方案，也不能应对超大光比的复杂情况。","b":false,"xe":"Although exploiting the camera's shadow latitude via 'underexpose rather than over' partially solves the high-contrast problem, it neither yields the best image quality nor copes with extreme contrast."},{"t":"p","x":"大光比环境，还有前期和后期的不同解决方案。","b":false,"xe":"High-contrast scenes have both on-location and post-production solutions."},{"t":"p","x":"前期平衡光比，在人像摄影中，最常用也是最好用的就是人工补光。在风光摄影中，渐变灰镜和摇黑卡是过去的解决方案。","b":false,"xe":"For balancing contrast on location, portrait photography's most common and effective method is artificial fill light. In landscape photography, graduated ND filters and black-card dodging were the old solutions."},{"t":"p","x":"现代风光摄影中，曝光合成的技术已经非常成熟。最简单的方法就是包围曝光再后期合成。","b":false,"xe":"In modern landscape photography, exposure blending is a mature technique. The simplest method: bracket exposures and blend them in post."},{"t":"p","x":"包围曝光，顾名思义就是在正常曝光的基础上，再故意拍摄几张过曝和欠曝的照片。这样大光比场景中的亮部信息，虽然在正常曝光的照片丢失溢出，但是在欠曝的照片中得以保留。同时大光比场景中的暗部信息，虽然在正常曝光的照片同样丢失，但是在过曝的照片中得以保留。","b":false,"xe":"Exposure bracketing, as the name suggests, means deliberately shooting over- and underexposed frames alongside the normal one. The highlight information lost in the normal frame is preserved in the underexposed one; the shadow information lost in the normal frame is preserved in the overexposed one."},{"t":"p","x":"最后我们再把这一系列照片用HDR自动合成软件、手动蒙版以及亮度蒙版等技术后期合成，就得到了所有细节都得以保留的场景。","b":false,"xe":"Finally, blend the series with automatic HDR software, manual masking or luminosity masks — and you get a scene where every detail is preserved."},{"t":"p","x":"包围曝光的核心思路，是在一张raw底片无法记录全部场景信息的情况下，用多张底片，分别记录下场景中的高光、中间调和阴影细节。从而用多张照片来完成“数码正确曝光”，最大化的记录下场景信息。","b":false,"xe":"The core idea of bracketing: when one RAW negative can't record the whole scene, use several negatives to record the highlights, midtones and shadows separately — achieving 'digital correct exposure' across multiple frames and maximizing the recorded information."},{"t":"p","x":"数码相机大都自带包围曝光功能，可以设置连拍张数，和每张之间的曝光值差异。到底设置连拍几张，曝光差值多少，还是可以参考直方图来决定：","b":false,"xe":"Most digital cameras have a built-in bracketing function where you set the frame count and the EV difference between frames. How many frames and what step to use? Again, refer to the histogram:"},{"t":"p","x":"连续包围曝光的系列照片中，最暗的那张左侧直方图没有被切断，最亮的那张直方图右侧没有被切断，这组照片就记录下了场景中的全部亮度信息，符合“数码正确曝光”。","b":true,"xe":"In a bracketed series, if the darkest frame's histogram isn't clipped on the right and the brightest frame's isn't clipped on the left, the set has recorded the scene's full brightness range — satisfying 'digital correct exposure'."},{"t":"img","f":"img-07","w":700,"h":457},{"t":"img","f":"img-08","w":700,"h":457},{"t":"img","f":"img-09","w":700,"h":455},{"t":"p","x":"上面第三张直方图合理的照片，就是由第一张欠曝和第二张过曝的照片进行合成得到的。","b":false,"xe":"The third, well-formed histogram above was produced by blending the first (underexposed) and second (overexposed) frames."},{"t":"p","x":"关于如何后期合成不同曝光值的照片，托马斯会在以后的教程中再详细阐述。","b":false,"xe":"How to blend frames of different exposures in post will be covered in detail in future tutorials."},{"t":"h","x":"总结","xe":"Summary"},{"t":"quote","x":"1. 数码时代，我们并不需要准确曝光，我们只需要用单张或者多张照片，记录下场景的全部亮度信息。直方图可以辅助我们确认，是否完整记录下了场景的亮度信息。 2. 正常光比环境，提倡“向右曝光”。大光比环境，记住“宁欠勿过”。 3. 人像前期补光，风光曝光合成，是解决大光比场景的最佳方案。","xe":"1. In the digital age, we don't need 'accurate' exposure — we need to record the scene's full brightness information with one or multiple frames, and the histogram helps confirm nothing is missing. 2. In normal contrast, 'expose to the right'; in high contrast, remember 'underexpose rather than over'. 3. Fill light for portraits, exposure blending for landscapes — the best solutions for high-contrast scenes."},{"t":"p","x":"欢迎关注@Thomas看看世界，","b":false,"xe":"Follow @Thomas Chu Photo,"},{"t":"p","x":"每个周日，学会一个摄影技能。","b":false,"xe":"and learn one photography skill every Sunday."},{"t":"img","f":"img-10","w":640,"h":313}],"titleEn":"How to Expose Correctly in the Digital Age"}