In color-key shots, an object of the photo composition is highlighted by making it appear in the original color, while the rest of the image is only shown in shades of gray or black and white. There are several ways to achieve this effect. You can work very precisely with the clipping tools and the layering technology of the photo editing programs Photoshop (Adobe) and Gimp (OpenSource). There are many tutorials that explain the sometimes very complex work steps involved in these programs.
Tamron SP 24-70 mm | f/2.8
The HDR display technology is primarily intended to compensate for the restricted dynamic ranges of digital sensors. If subjects have very bright and at the same time very dark areas, the details in the (overexposed) bright and (underexposed) dark areas disappear with a single shot. Just think of the window flooded with daylight, which - when properly lit - makes the surrounding objects disappear in the dark. With HDR technology, multiple shots of a subject with different exposure values are now taken and then offset by software so that the structures are retained in all areas.