HDR preview

1) You have to take different photos in different exposers by yourself. Manually change the ISO and shutter speed

2) HDR blending software, a camera, and a tripod.

3) Taking better pictures is why someone may take an HDR photo. With a landscape of buildings and sky, you can get the dark and light versions and combine them together to look 3D or more realistic. 

4) After combining the photos you can see how the effect really goes into play. You can see the contrast between the different photos that you can't see in just one normal photo.