1. Photo: By taking multiple exposures at different exposures/apertures (f-stop) we can capture parts of the scene that were not included in any of the exposures. With multiple exposures the dynamic range of the scene will only be about 9 + 4 = EV 12, but by combining the exposures we can capture parts of the scene that were not included in any of the exposures. A sequence of 3 exposures can capture about 13 EV of dynamic range.
Each individual exposure can be viewed and edited in the camera monitor or you can merge the images into a single image later if needed. Photo: -2 EV exposure, -2 EV exposure, -2 EV exposure, -2 EV exposure, + 2 EV exposure, and + 2 EV exposure. Merge the exposures into a single image in an image editing program such as Photoshop. This new combined exposure has a dynamic range of 13 EV.
2. Expose for the highlights. Expose +4 EV to over expose the highlights to make sure the brightest parts of the image are not lost. Then increase exposure by 2 EV to under expose the shadows. Let's also assume we don't want to blow out the brightest parts of the image, so the last step is to bring these parts down to approximately the correct exposure. To accomplish this we use a combination of the +2 EV and -2 EV exposures. We can determine the correct exposure by using the histogram on the camera monitor or in post processing. To show you how the process works we will use a scene with a dynamic range of about EV 13.
A simple method to tone map the HDR image is to use the default settings for the HDR Pro plugin from RawTherapee. The plugin has a standard slider to control how the tones are compressed. The default is 100%, which is to not compress the tones at all (see first image below). If the dynamic range of the scene is very high (e.g. -10 EV) you will get a very surrealistic looking image.
I then take a second exposure at EV +2 (the same exposure time as the base) and I shoot a third exposure at EV 0 (a completely different exposure time). Now I have the EV 3 exposure for the highlights and the EV 0 exposure for the shadows. In most of the examples shown you can see both the highlights and shadows are captured in good detail. In order to get these exposures I use a tripod. I then combine the three exposures into an HDR image using Photoshop. The original three exposures or base images are shown below: 827ec27edc