NatureScapes.Net - The High Dynamic Range (HDR) Landscape Photography Tutorial

Published July 2006

Here is a comparison that shows the difference in processing a sequence of three 5D exposures. The input images were taken at +/-2 EV, then combined and tone mapped with default settings except for the Smoothing setting change to the second example. The third example was made by down-sampling the 5D files to 3072x2048 (the same size as 10D files). No other modifications have been made.

5D File, Smoothing “High”
5D File, Smoothing “Medium”
5D File Down-sampled, Smoothing “High”

I ran into this same problem in the snowy sunset example just above, which is based on 5D frames as well. I was able to side-step the tonal artifacts in that case by cropping a little from the bottom and right of the images before combining them into an HDR file.

MultimediaPhoto is looking into both of these issues, and hopefully fixes will be coming before too long.

In this section I provide an overview of my current workflow for creating multi-frame stitched HDR images. There are four main tools involved: Rawshooter Premium, Panorama Factory, Photomatix Pro and Photoshop CS2. Because of the complexity of working with everything, I will not go into details of any one tool, but will just mention some highlights at each major stage of work.

The example will produce a tone mapped image from the following sequence of 24 frames:

The base images were shot at 1/20s, f/16, ISO 400. (I did not really intend to shoot at ISO 400, but we will see how it turns out.) The camera used was a Canon EOS 5D with Sigma 12-24mm f/4.5-5.6 lens zoomed to 15mm. The camera was tripod mounted, and the shutter was tripped with a remote release cable. The exposure sequence was taken using auto-bracketing at each rotation point across the field of view, using an interval of +/- 2 EV. I did not adjust the camera to rotate around the nodal point. All images were shot in RAW mode.

The example screenshots in this section are taken from a desktop workstation (AMD Athlon 64 X2 4800+ dual core system with 3 GB of RAM visible) running Windows XP SP2.

The main difference in this workflow compared to the previous ones seen for processing single frame HDR images, is that stitching work also must be done. You will need to decide whether to stitch first and work on HDR second, or the opposite. I strongly favor stitching first because HDR processing involves a lot of tone curve and local contrast optimization work. As such it should only be performed across a set of fully integrated images covering the field of view. Otherwise the tone mapping will create localized enhancements within the frames that stop at the individual frame borders. This will do poorly when fed into the stitching software.

In order to stitch first and process HDR second, it is helpful if the stitching software has the capability of stitching several image sets using identical control points. This will cut down the amount of repetitive stitch work and also ensure better registration of the images fed to the HDR tool. It does presume that there is minimal or no motion of solid objects within the field of view. If any subject matter is moving, then the stitching can not be done with identical control points. It is best in this case to fine tune each stitch to ensure a seamless job, and then worry later about how to deal with blurring or ghosts introduced by the HDR tool when it combines the stitched images.

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