Lippmann (or interferential) photography is the first and only analog photography method that can capture the full color spectrum of a scene in a single take. This technique, invented more than a hundred years ago, records the colors by creating interference patterns inside the photosensitive plate. Lippmann photography provides a great opportunity to demonstrate several fundamental concepts in signal processing. Conversely, a signal processing perspective enables us to shed new light on the technique. In our previous work (G. Baechler et al., 2021), we analyzed the spectra of historical Lippmann plates using our own mathematical model. In this paper, we provide the derivation of this model and validate it experimentally. We highlight new behaviors whose explanations were ignored by physicists to date. In particular, we show that the spectra generated by Lippmann plates are in fact distorted versions of the original spectra. We also show that these distortions are influenced by the thickness of the plate and the reflection coefficient of the reflective medium used in the capture of the photographs. We verify our model with extensive experiments on our own Lippmann photographs.

中文翻译：

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李普曼摄影：信号处理视角

Lippmann（或干涉）摄影是第一个也是唯一一个可以在单次拍摄中捕获场景的全色谱的模拟摄影方法。这项发明于一百多年前的技术通过在感光板内部产生干涉图案来记录颜色。Lippmann 摄影提供了一个很好的机会来展示信号处理中的几个基本概念。相反，信号处理的观点使我们能够对这项技术有新的认识。在我们之前的工作中（G. Baechler等人。, 2021)，我们使用我们自己的数学模型分析了历史李普曼板块的光谱。在本文中，我们提供了该模型的推导并进行了实验验证。我们强调了迄今为止物理学家忽略其解释的新行为。特别是，我们表明由李普曼板产生的光谱实际上是原始光谱的扭曲版本。我们还表明，这些失真受板的厚度和用于拍摄照片的反射介质的反射系数的影响。我们通过对自己的李普曼照片进行大量实验来验证我们的模型。