DISCUSSION

A major advantage to using HDR techniques is the speed with which a researcher can ensure that they capture needed information in different lighting conditions, without investing time in minute adjustments of lights. While it is always preferable to create specimen photos in controlled settings with good lighting, HDR methods can be especially useful when specimens are mounted or otherwise difficult to move into better-lit conditions, such as large, fragile objects on shelving. It is also useful for any specimen or landscape where surface detail is important, and should be easy to carry out in field situations. In situations where speed is required, HDR techniques may make the difference between obtaining ten usable shots, or one traditionally well-lit shot.

It is important to note that, though HDR processing and detail enhancement tonemapping might not directly improve an image over the metered exposure, the added precision and workflow changes can be useful in any case. A HDR file can be virtually reexposed to produce exactly the exposure needed after the fact, and many image processing operations produce more accurate output when performed on floating point pixels. The simple act of shooting a bracket increases the likelihood of getting a usable image, even if no HDR assembly is done.

Furthermore, properly processed HDR-derived images show dramatically reduced noise and grain. As with the traditional photographic exposure blending technique, the random noise introduced by the photographic medium in one image will be overwhelmed by values from the other images. It is therefore sometimes worthwhile to shoot a bracket and generate a HDR image simply to re-expose it to the original EV value in software. If the additional detail recovered through HDR processing is not necessary, most HDR software also includes a pure exposure blending mode, which takes advantage of the software's alignment capabilities.

Shooting for HDR requires less equipment to be carried in field or museum settings, as the only required equipment is a camera, tripod or other stabilizer, and a larger than usual number of memory cards. The processing is relatively straightforward using the tools we tested, all of which are inexpensive. Much of the detail enhancement available in the software is automated, so refining the image is much simpler than a complex series of enhancements to a single exposure in Photoshop. With modern cameras, in addition, the shooting process is constant, regardless of illumination, and the researcher is able to get into an efficient rhythm.

Lastly, HDR processing reduces the number of irrevocable decisions that must be made when taking specimen photographs. The camera can be set up, and shots taken as quickly as the specimen can be repositioned. In exhibit spaces, usable images can be shot almost at walking speed, without inconveniencing museum visitors or staff.

However, for specimen photography that, by convention, has a specified direction of light to show particular features (more common in invertebrate paleontology), HDR cannot be used to add that directional light in processing. Any needed directional lighting should be added at the time of shooting the bracket.

For reference photos to accompany notes taken on museum visits, in field situations, or even for publication (depending on requirements), HDR can provide a significant visual advantage. In less constrained situations where copy stands, lights, and time are available, conventional single exposures can yield similar results to an HDR image—but the HDR image still has significant advantages, due to the greater post-processing flexibility and accuracy inherent in the format.