一张照片为什么看起来像胶片

胶片感来自影调和颜色怎样形成，颗粒、暖色和发灰的暗部只是表面。

说一张照片“有胶片感”时，人们最先想到的往往是颗粒、偏暖的颜色和发灰的黑色。这三样在手机滤镜里最容易做出来，也最容易被认出是后加的。真正让人觉得像胶片的，是更底层的几件事。

影调曲线

胶片对光的反应可以画成一条特性曲线。暗部有一段“趾部”，亮度慢慢抬起；中间是一段斜坡；亮部有一段“肩部”，越亮越平缓。数码传感器在记录时接近直线，直到满阱为止。胶片照片里那种柔和的高光、连贯的过渡，大多来自这条曲线的两头。详见理解高光过渡。

颜色随亮度变化

彩色胶片用三层染料记录颜色，每层的感光和染料特性并不完美匹配。结果是颜色会随亮度轻微漂移：同一件红衣服，在阴影里和在阳光里不是同一种红。很多胶片在最亮和最暗的地方饱和度也会降下来。数码相机配置文件通常让颜色在各个亮度上更一致，这本身没有错，但看起来更“干净”。

颗粒跟着影调走

胶片颗粒是显影后的银粒或染料云，它的大小和可见程度随密度变化，在中间调最明显。后期加的颗粒往往在整张照片上均匀铺开，连纯白的天空和纯黑的阴影里也一样，所以看着像一层纱。见胶片颗粒和数码噪点。

扫描和冲洗也是一半

你在屏幕上看到的胶片照片，几乎都经过扫描。扫描仪、冲洗店的反转设置和之后的调整，对颜色和反差的影响可能比胶片本身还大。所以同一种胶片，在不同人手里可以很不一样。

拍的时候就决定的东西

还有一些和胶片无关，却常被归到“胶片感”里：老镜头较低的微反差、较慢的快门带来的轻微模糊、因为一卷只有 36 张而更慎重的构图。这些在后期里很难补出来。

FilmLook 的胶片感评分看的就是这些形成方式，而不只是表面效果。只加颗粒和暖色的照片，分数不会高。

下一篇：胶片颗粒和数码噪点

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All guides

What makes a photograph look like film?

The film look comes from how tone and colour are formed; grain, warmth and faded blacks are only the surface.

When people say a photo "looks like film", they usually mean grain, warm colour and faded blacks. Those three are the easiest to add with a phone filter, and the easiest to recognise as added. What actually makes a picture read as film sits deeper.

The tone curve

A film's response to light can be drawn as a characteristic curve. In the shadows a "toe" lifts brightness gradually; the middle is a straight slope; in the highlights a "shoulder" flattens as exposure rises. A digital sensor records close to a straight line until it saturates. Much of the soft highlight and smooth transition in film photographs comes from the two ends of that curve. See understanding highlight roll-off.

Colour that changes with brightness

Colour film records colour in three dye layers, and their sensitivities and dyes never match perfectly. The result is that colour drifts slightly with brightness: the same red coat is not quite the same red in shade and in sun. Many films also lose saturation in the brightest and darkest areas. Digital camera profiles usually keep colour more consistent across brightness. That is not a fault, but it looks "cleaner".

Grain that follows the tones

Film grain is developed silver or dye clouds, and how large and visible it is changes with density; it shows most in the midtones. Grain added in editing is often spread evenly across the frame, into a white sky and a black shadow alike, so it sits on top of the picture like a veil. See film grain and digital noise.

Scanning and processing are half of it

Almost every film photo you see on a screen has been scanned. The scanner, the lab's inversion settings and the adjustments after them can change colour and contrast more than the film itself. The same film can look very different in different hands.

What is decided when you shoot

Some things have nothing to do with film but get counted as "film look": the lower micro-contrast of older lenses, slight blur from slower shutter speeds, the more careful framing that comes from having 36 frames on a roll. These are hard to add afterwards.

FilmLook's Film Look Score looks at how these qualities are formed, not at surface effects. A photo with only added grain and warmth will not score highly.

Next: Film grain vs digital noise

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