When shooting virtual tours, we take three to nine images, each at a different exposure. Then we combine these images into one image. Yes, we use the M setting on our camera. And no, it doesn’t stand for missed another one. The reason we take multiple exposures is so that we can achieve what is called High Dynamic Range (HDR). HDR gives us expanded capabilities which enable us to capture the entire brightness range of the scene and adjust the final image to look just right.
In this image, the five exposures are each one stop apart. On the far left, you can see detail in the sky. On the far right, you can see detail in the shadows. When combined these images can have various outputs, depending on the editor.
We prefer the photographic look of the center image. Although the image on the left is useable, it doesn’t look realistic because the shadows are boosted too much. The image on the right is an art project, which is fine if that is the intent.
Where a single exposure gives a reasonable image most of the time, an HDR makes a good exposure possible in places where there is a high dynamic range. Imagine having to get the same exposure when shooting photos all the way around in a circle. Facing one direction, the photos would be directly into the sun. Facing the other, the sun would be lighting the scene. This is why HDR is important. It prevents the images from being a complete disaster. When we combine the HDR images into a panorama by careful adjustment, the entire scene becomes viewable. Special software also helps blend the exposure from one direction to the next. No one likes skies that are so blown out it looks like a blizzard is coming, or shadows that obscure large portions of an image.