High-dynamic-range imaging (HDR) is a technique to produce images that have a greater dynamic range of luminosity (that is, contrast ratio) than could be displayed through the display medium, or captured with the camera using a single shot. There are two main ways to create such images—using special image sensors, such as an oversampled binary image sensor, or the way we will focus on here, by combining multiple Standard Dynamic Range (SDR) images to produce a combined HDR image.
HDR imaging works with images that use more than 8 bits per channel (usually 32-bit float values), allowing a much wider dynamic range. As we know, the dynamic range of a scene is the contrast ratio between its brightest and darkest parts.
Let's take a closer look at what the luminance values are of certain things that we can see. The following diagram...
