What we are familiar with on a small scale at home, when we have collected, dried and pressed leaves in the fall, also exists in science − albeit on a completely different level and with considerably more effort: In herbaria, plants or parts of plants are collected, the respective name is added, as well as the collector and the place of discovery. One of the purposes of such a collection is to compare the archived plant with others that are still growing. Herbaria play a particularly important role in botany, but other sciences, such as archaeology, can also benefit from them. Last but not least, such a collection also offers everyone who is interested exciting insights and orientation in the world of flora. Whether science or “just” amateur interest – when an herbarium is digitized, a large audience gains access to a huge database with detailed illustrations and associated information at the same time and without significant effort.
Impressive technology for the highest demands
One such digitization project is currently underway at the Thuringian University and State Library Jena (ThULB). The huge holdings (approx. 4 million plant specimens) of the Haussknecht Herbarium (JE) (https://www.thulb.uni-jena.de/thulb/standorte/herbarium-haussknecht) are being digitized here. The collection was named after the pharmacist and botanist Carl Haussknecht (1838-1903), who laid the foundation in 1896.
In addition to the collection of dried plants and other plant specimens, the Haussknecht herbarium (JE) also includes an important specialist botanical library and an archive on the history of botany. The digitized plant specimens are made available to the public via the virtual herbarium (https://www.herbarium.uni-jena.de/32/virtuelles-herbarium).
Thanks to generous funding from the Thuringian Ministry of Education, Science and Culture, the ThULB, together with the Senckenberg Institute for Plant Form and Function Jena (SIP), was able to purchase our high-performance scanner book2net Archive Pro A2+ to expand the digitization possibilities especially for herbarium specimens.
The book2net Archive Pro has been equipped with our M150 camera, which now also uses the new “Focus Stacking Tool” for the first time. This is an ingenious method for capturing every area of the objects to be digitized in detail and with absolute sharpness.
For a true-to-scale, brilliant image in high resolution, which also guarantees a constant depth of field across the entire area being captured, an even surface level is the ideal prerequisite. However, plants or parts of them, such as flowers, do not have flat surfaces, but three-dimensional structures. As it is unthinkable to “flatten” such precious unique specimens using a glass plate, focus stacking, also known as focal plane merging or focus blending, is used in this case to create images with exceptional depth of field.
The new focus stacking tool
Focus stacking is a method of maximizing the depth of field of an image.
Several images of an object are taken within a very short time, whereby the focus point is shifted slightly with each image. In this way, a new, very small area is precisely captured step by step for each image. These images are then stacked using the software, i.e. combined in such a way that only the sharp areas of each photo are integrated into the final image. The end result is a consistently sharp image with maximum detail.
We offer two methods for this: firstly, changing the focal plane by moving the camera to a new position on the camera slider, whereby the secure fixing on the slider also prevents any shifts or distortions, and secondly by controlling the lens and the focus setting via a motorized focus. In both cases, the process can be precisely programmed using presetting in our scanning software. The result is a razor-sharp image of incredible detail, which can provide scientists with new information for analysis and comparisons and is a real eye-catcher for aficionados.
However, focus Stacking is not only the ideal solution for the digitization of herbaria but is also suitable for all collections whose objects have three-dimensional structures and whose details are to be examined more closely: whether insects, coins, pottery fragments, textile fragments, etc. – there are virtually no limits to the possible applications.
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