HDR Creation
This page outlines the special workflow considerations when working with HDR photography.
Overview
Like with any other kind of photography, it is essential to have a consistent workflow with HDR images. Because of the large number of exposures, additional HDR files, and the larger amount of computing time compared to a RAW workflow, there are some important considerations. In addition to the basic difficulty of keeping all the files organized, metadata becomes a greater problem. Many tone mapping applications don’t pass metadata through to the tonemapped image, so it becomes the photographer’s responsibility to re-embed the correct information.
Filenaming
The choice that must be made when naming HDR files is whether to use sequentially numbered file names and rely on metadata and visual inspection to identify HDR brackets, to use batch names which separate each bracket, or to separate each HDR bracket sequence into its own folder.
Sequential numbering is a fast approach, but it will be harder to identify bracket sets. Sequential file numbers in a bracket sequence would look like: Stack_090729_8456, 8457, 8458, etc. Same scene, but different exposures. Bracket sequences are identified visually or by metadata (added during ingest or editing), and the merged HDR files are named after either the first number in the sequence or the "normal" exposure. (Stack_090729_8456.hdr).
The main advantage of sequential numbering is that it can get you right to work. Because merging bracket sequences to HDR files and tone mapping are so time consuming, it may be to the photographer's advantage to start producing final images as soon as possible. However, this approach can easily lead to post-production confusion if the HDR scenes look similar to one another or if there were multiple versions of a shot. Do you really want to examine each frame to figure out which sequence has the fork on the correct side of the plate? Sequential numbering can also become a problem if files from a shoot mix Low Dynamic Range (LDR) files and HDR bracket sequences. There is no way to identify which files are HDR sequences outside of an image browser, such as Bridge.
--screenshot of a folder of mixed LDR and HDR images in Bridge, and in the finder.
Using batch numbers to identify each bracket sequence will be more time consuming during image ingest and editing, but can help to identify the bracket sequences quickly: Stack_090729_029a, 029b, 029c. Merged HDR files would be named for the batch number (Stack_090729_029.hdr). Batch numbers can speed your workflow up in post-production, but will take time up front as each set of brackets will have to be renamed separately. The file naming process can be sped up with a workflow tool capable of sophisticated renaming such as Photo Mechanic. Batch names can also solve the problem of mixing LDR and HDR in a single shoot; files with a letter in their file name are easily recognized as HDR sequences.
--screenshot of mixed LDR and HDR files with batch names in the finder.
When shooting a large set of bracket sequences (such as for an HDR panorama), it is advisable to sort each set of images into discrete folders. Images are kept in a job folder, then shot folders for each bracket sequence. The HDR file is then named for the shot folder. While separating the files into folders can be time consuming when capturing to card only, it is easy to set up separate capture folders for each bracket sequence when shooting tethered. This method is recommended, particularly when shooting panoramas or when the files will be handed off to a retoucher or other post-production person who wasn't at the shoot.
--screenshot of HDR shot folders.
Breeze Systems offers a helpful solution for tethered HDR shooting on a Windows platform. DSLR Remote Pro allows the computer to control the camera to shoot an automated bracket sequence, which it can name with a batch number (123a, 123b, 123c, etc.). This can be used in conjunction with Photomatix's batch processing function to create HDR files on the fly.
Read more about file naming in the file management section...
Metadata
Files shot for HDR and the final, optimized images need to have embedded descriptive metadata just like any other image file. Because we have the ability to embed descriptive information, we can identify bracket sequences in our Digital Asset Management software by the inclusion of custom keywords and categories.
Many HDR tonemappers don’t pass a bracket sequence’s metadata through to the tonemapped image. Photomatix for instance will preserve partial IPTC metadata in a tonemapped image, but only through a session and only when using rendered files to create the HDR file (i.e. if the HDR file is created, saved, and closed, then reopened later, there will be no metadata, even if the file itself has metadata embedded, and there will be no metadata at all if the HDR is merged from RAW files).
It is essential to test the software you’re working with and maintain a consistant workflow. Constant vigilance!
HDR workflow
With the exception of file naming, and perhaps some additional folders, files shot for an HDR bracket should to be treated like any other files you shoot. HDR image creation will most likely resemble an optimized image workflow.
Read more about an optimized image workflow...
When to merge to HDR
Archiving HDR
The primary difference between an HDR and an LDR workflow is the creation of the HDR files themselves. Due to the time involved in the creation of an HDR file (particularly when the source images were shot handheld or are parts of a panorama), HDR files should be archived in the same manner as raw files. Keeping these files in your archive means that an HDR image can be revisited and re-tonemapped endless times, without having to take time to recreate the HDR file. As this technology develops and as HDR displays become commercially available, preserving these files may become a boon.
Depending on the time put into their creation, tonemapped images may be saved as an intermediate step between HDR and optimized masterfile. Alternatively, the tonemapped result might be preserved as the base layer in a masterfile.
HDR post-production
