Natural News

Natural News

Building the ANHC Herbarium's Imaging Station

Arkansas Natural Heritage Commission - Wednesday, January 29, 2020
by Molly Robinson

To the delight of its staff and volunteers, the ANHC Herbarium is now ready to resume imaging its collection of over 15,000 accessioned plant specimens as part of its digitization efforts. The ANHC Herbarium completed its first round of imaging in late 2018 (See ANHC Herbarium Digitization Underway).

In a little over a year, the ANHC Herbarium has accessioned approximately 3,000 additional specimens, making it the fastest-growing herbarium in Arkansas. These specimens and their labels have been mounted to archival paper, stamped with the official “Arkansas Natural Heritage Commission Herbarium (ANHC)” stamp, and accessioned with a stamped number in addition to a unique barcode number. The stamped number indicates the number of unique records in the collection; large specimens that need more than one herbarium sheet have the same stamped number to link them together. Each herbarium sheet has a unique barcode number, which is used to link the specimen image to the herbarium database record.

With several thousand more specimens in the queue to be accessioned and more specimens collected every year, there will be ongoing demand for imaging at the ANHC Herbarium. The new imaging station will meet this demand for ANHC and can even support the imaging needs of other herbaria in Central Arkansas. This would not be possible without the passionate volunteers who will be the primary operators of the ANHC imaging station. Trained herbarium volunteers and interns can image up to 100 herbarium specimens per hour.

Of the eight herbaria in Arkansas, ANHC is the first to have a permanent imaging station. The small market for ready-made herbarium imaging solutions demands designing and building an imaging station from scratch. An imaging station has three basic parts: a light box to stage the specimen inside with bright and even illumination, a digital camera, and a computer connected to the camera for shooting and uploading the images. Building ANHC’s imaging station required lots of research, networking, and manual modifications to commercially available equipment.

The ANHC Herbarium staff had to do extensive research while selecting a camera and its necessary accessories, as well as compatible photography software. ANHC Herbarium staff consulted dozens of written materials from other herbaria, reviewed many candidate camera models, and corresponded with leading experts in herbarium digitization. Special thanks to Diana Soteropoulos, the Arkansas Herbarium Digitization (AHD) coordinator (see ANHC Steps Up to Continue Arkansas Herbarium Digitization Project), for sharing her expertise in selecting a camera and imaging-related software.

The most challenging part of constructing the imaging station was the light box. Until 2015 it was possible to purchase a light box custom-designed for imaging herbarium specimens. Unfortunately, these specially designed light boxes and even the bulbs that illuminate them are no longer available in the United States. So, the ANHC staff reached out to other herbaria to learn which commercially-available light boxes have worked the best for imaging herbarium specimens.

Based on recommendations from Dr. Gil Nelson, director of iDigBio, and Katelin D. Pearson, project manager for the California Phenology Collections Network, ANHC ordered a light box designed for photographing e-commerce merchandise. It is large enough inside to stage herbarium specimens and is built with a window in the lid for photographing subjects from above. It also comes with a reflective curtain for covering the door on the front panel of the box, which helps retain light while photographing specimens. Still, the purchased light box was not designed for herbarium imaging and required a number of modifications before it could be used for this purpose.

First, the light box lacked equipment that would allow the position of the camera to be adjusted up and down and side-to-side. Manufactured camera stands and mounts can cost hundreds of dollars. Fortunately, other herbaria had already confronted this issue and found a budget-friendly solution: building a custom camera mount that could be secured to the lid of the light box. Using specifications provided by the Consortium of Pacific Northwest Herbaria, ANHC’s Conservation Data Specialist and carpenter extraordinaire, Scotty Winningham, generously constructed a custom camera mount for the herbarium.

Then, ANHC Herbarium staff removed the front wall panel from the light box to create a wider doorway for specimens to be safely maneuvered into and out of the box. A wooden dowel was sewn into the bottom of the curtain to make it easier to move the curtain out of the way while putting a specimen in the box. While the curtain is lowered, the weight of the dowel also encourages the curtain to hang flat, thus trapping more light. To achieve a black border around the specimen in the photos, the floor of the light box was lined with black felt. On top of the black felt, a ruler with the ANHC logo, a small color chart (used for color correction when editing photos), and a blank herbarium sheet were secured to guide the positioning of specimens in the box.

Initial testing of the imaging station revealed that the light box failed to provide enough light to help the camera pick up the fine details necessary to study plant specimens from images. The box also illuminated the specimens unevenly, leaving sections obscured by shadows. Herbarium staff researched ways to supplement the lighting inside the box to achieve the correct color temperature and level of brightness. After corresponding with Jason Best, director of Biodiversity Informatics at the Botanical Research Institute of Texas, it was decided to use about 16 ft. of LED-bulb strip lights, which were installed inside the light box to make the lighting throughout the box more even while also boosting the amount of light in the box.

These many modifications were well worth the effort. Specimens imaged with ANHC’s new imaging station are crisp, clear, and capture an even finer level of detail than herbarium staff anticipated. This is a major milestone for the ANHC Herbarium, which can now digitize its collection with in-house equipment. The ability to image specimens as needed on a daily basis will speed up the process of sending new specimens to researchers at other locations and make the data globally accessible with online images.

Imaging thousands of specimens in Arkansas would not be possible without dedicated interns, students, and volunteers. Thank you to the passionate individuals who support the ANHC Herbarium and other herbaria in the state.

Recent Posts