Capturing images of types presents many challenges if the end results are to be scientifically valuable, virtual representations of physical specimens. A primary reason for undertaking such an effort is to enable scientists in remote locations to examine types without the need to handle them, with the ability to compare high-quality visual representations. This will only be worthwhile if the images carry sufficient information for the remote taxonomist to be able to state that the specimen in hand being compared with the type image is NOT of the same species. The effort will be of even higher value if the images allow for positive identification. If neither criterion is met, the imaging effort has little value.
In an attempt to present the best possible virtual access to types, two basic principles should be followed:
- Always consult specialists for the taxonomic groups being imaged to determine which characters need to be documented in order for the images to be scientifically informative.
- The images produced should faithfully represent the specimen as closely as possible.
The size and type of specimen will determine the most appropriate imaging system. In generally, with decreasing specimen size, problems with a lack of depth of field increase. This is particularly true when imaging subjects such as tiny insects using a microscope system. When specimens are very small (3 mm and less), optical limitations of equipment preclude obtaining an image with depth of field that spans the entire specimen in a single shot. The process of imaging insect specimens and other small groups is very different from capturing image data for other biological specimens, such as herbarium sheets, which are virtually two-dimensional and require simple scanning, or vertebrate specimens that are sufficiently large to reduce or eliminate the depth of field problem.
following are imaging systems that have been successfully
used by the Museum of Comparative Zoology for imaging insects
- other imaging hardware and software could certainly be used,
and may be more appropriate for other taxonomic groups.
1. Specimens >= 15 mm long
D1X digital camera with NikkorMicro 105 mm lens
by incandescent light (large specimens and those with high
with the Microptics
ML-1000 system (small specimens, those with low reflectivity,
and microscope slides)
2. Specimens < 15 mm
3. Specimens <15 mm that require full depth of field image
KY F75 digital camera mounted on a Leica
data fed directly to Syncroscopy Auto-Montage
image processing system
with a Fostec fiberoptic light source
With the first two systems, captured images are virtually ready for incorporation into the image database, requiring only size modification and change of file format, both processes largely automated. For the third situation, each final image is the result of a digital assembly of a stepped series of images of the same structure taken at different focal distances, using the Auto-Montage image processing software.
Digital Documention Procedure
- The type specimen is located in the collection and its label data are compared with the entry in the type database. Even with a complete database, occasionally type specimens may be absent from the registry, such as specimens recently returned or donated to the collection, or specimens not initially recognized as primary during compilation of the database. Also, species in the type database may be a syntype series, in which case the specimen in best condition should be selected for photography. In the event that another specimen is subsequently designated the lectotype by a specialist, that specimen should be photographed as well.
- The specimen and all its labels are photographed - each imaged specimen receives a label indicating that it has already been documented.
images, captured as high resolution, archival-quality TIFF
files or low compression jpeg files, are assigned unique
codes and placed in directories named with a combination
of the species original name and its unique catalog number.
- Large image raw files (TIFF and low compression JPEG files) are converted into smaller, lower resolution JPEG images for incorporation into the online database. Two JPEG versions are made: small (max. 500 pixels wide) and large (max. 900 pixels wide). Both the original raw files and processed smaller files are stored in two copies of hybrid format (readable on any platform) CD ROM's and a single copy data DVD. This ensures that there are at least three independent copies of each image, stored at different locations. A database of raw image files can be maintained in addition to the taxonomic database where processed images are stored. It may also be prudent to store image databases at remote sites, similar to the Harvard University Library's centrally managed Digital Repository Service. These services typically include back-up, monitoring to prevent format obsolescence, and strategies for data migration. It's entirely conceivable to have massive databases that exceed 1000 GB.
- JPEG versions of images are linked to individual species records in the type database and assigned captions describing the structure or shot.
this endeavor will require a well-trained technical staff
with competence in imaging and computers. The average number
of type specimens a properly trained technician is capable
of documenting in one day varies greatly depending on the
taxon, size of specimens, number of required shots, the need
to create composite images, and the type of equipment used.
For example, photographing relatively large animals such as
butterflies, fish, frogs and crabs requires no composite imaging,
and one can expect to document between 30 to 50 species a
day. At the other end of the spectrum, very small specimens,
such as many ants, gastropods, flies and small crustaceans
require multiple images (between 5 and 20) for each final
composite photograph. In such cases only 4 to 14 species per
day can be documented. Typically, 3 to 5 image views of each
specimen are captured, in addition to associated labels. This
includes dorsal, ventral, lateral and frontal views. Certain
groups (e.g. some scarab beetles) require up to 8 individual
specimen images if such action is suggested as a requirement
for positive identification. Close-ups of the head, mouth
parts, legs or other areas may then be needed.
here for more information
on family-specific requirements.