Intro to High Dynamic Range (HDR)

This post on photography tips is about HDR. HDR stands for High Dynamic Range and it is an art of photography that is getting popular in the world of digital photography these days. Surf around for photography tips and you're bound to stumble upon some HDR-related resources. A regular photo taken with a single shot has a limited dynamic range. This is how I understand it: imagine the darkest and brightest tones possible in this whole universe representing the furthest left and right corners of a histogram respectively. A camera's sensor is not able to capture the entire range of tones on this histogram. There is a point on the left beyond which everything is recorded as black and likewise, there is a point on the right beyond which everything is recorded as white. The range of tones between these two points is the sensor's dynamic range.

In a bright scene, the dynamic range shifts to the right and correspondingly in a dark scene, the dynamic range shifts to the left. The problem occurs when there is a scene with high contrast - some parts are very bright and others are very dark. With regular photos, setting the camera to correctly expose the bright parts will cause the dark parts to be under exposed. On the other hand, setting the camera to correctly expose the dark parts will cause the bright parts to be over exposed. Setting the camera's exposure in between the two has been the best solution before the advent of HDR photography. It resulted in slightly overexposed and underexposed parts but it was the lesser of evils.

With HDR, several shots are taken of the same scene but with different exposure settings. The idea is to have a set of identically composed photos where each correctly exposes a part of the scene. The pictures are then merged together using the appropriate software such as Adobe Photoshop. The resultant HDR image has a much larger dynamic range and ideally, everything of the scene is perfectly exposed. While it is possible to create a HDR image with only two or three photos in the set, I find that the best results require at least five. There was a group test in Digital Photo magazine a few months ago on HDR software. Photomatrix Pro v3.0 came out first. A free HDR software called Picturenaut was also reviewed. It didn't do very well in the group test but hey, it's free.

The picture on the top left is a HDR image composed from a set of five photos. It is a picture of the facade of Nymphenburg Palace in Munich. So, how did I take a set of photos with different exposure settings suitable for creating the HDR image above? I've found various photography tips on how to do this and settled for the method I feel is most convenient. First, I mounted up my camera on the tripod (since all photos in the set must be identically composed) and properly composed the shot. I set my camera to matrix metering, which is a Nikon proprietary light metering mechanism (Canon has an equivalent as well). I took the first shot without any exposure compensation i.e. 0 EV. Then I set the EV to -0.7, -1.3, +0.7 and +1.3 respectively for the next four shots. The picture on the right is also a HDR image. It was taken at the rear of Nymphenburg Palace.

HDR is not the best form of photography. There are benefits and drawbacks to it. In my next post, I'll share more pictures and thoughts on HDR photography from my outing to Nymphenburg Palace. I'll show you some HDR and non-HDR images for you to judge.

I hope you found this post on photography tips for HDR beneficial.

joel@shutteria.com