This page contains a Flash digital edition of a book.
Live Hydrated Specimens


Figure 5 : Immature strawberry fl ower (Fragaria, family Rosaceae) at 5 kV and 19 mm working distance. Immature fruit showing achenes with stigmas and styles protruding. Image taken in 1976 [ 7 ]. Image width = 2.54 mm.


Figure 6: Moth fl y (family Psychodidae) at 5 kV and 19 mm working distance. These harmless 1 mm fl ies can enter the house through a window screen and breed in sink and bathtub drains. Image taken in 1976 [7]. Image width = 271 µm.


at a place on the specimen that would be out of the recorded frame whenever possible. Images were generally recorded from the high-resolution recording CRT, which was calibrated and standardized at a lens aperture of f 8 and 2,500 lines per frame with a total record time of 60–70 seconds. Black levels and highlight saturation were experimentally determined for each type of fi lm used or calibrated to the dynamic range of the digital acquisition hardware.


Results


Figures 1 through 6 show that early trials and experimen- tation in 1973 and 1974 yielded results of surprisingly good quality. All these images were made of insects or fl ora in their natural state as live unfixed specimens. Many of these and later images were subsequently widely published in trade and consumer publications and shown in exhibitions [ 2 – 7 ]. Figure 7 [ 8 ] shows a more recent, digitally acquired, color image made with the Wideband Multi-Detector Color Synthesizer system [ 9 ].


Discussion


Figure 7: Anopheles stephensi mosquito (female) at 5 kV and 14 mm working distance. This species is predominant in Asia and is a disease vector for the Plasmodium protozoa that causes malaria. Color synthesized with the Scharf multi-detector color SEM. Image taken in 2006. Image width = 2.26 mm.


14


It was not uncommon for many live insects and arachnids to keep moving for quite some time while being observed, ruining many a still image. So beginning in 1988, some of the fi rst SEM, NTSC-TV video recordings were made direct to S-VHS and later to DVCAM format. T is was possible because the ETEC Autoscan allowed real-time NTSC or PAL video scanning with a separate video scan generator and alternate high speed defl ection coils used exclusively for the TV scanning system. T e TV scan rates resulted in lower beam dwell times at each image point and thus made possible the use of larger spot sizes with more current, improving S/N. Similar to the still images, as the magnifi cation increases, the spot size must decrease causing a smaller beam current and a lower S/N. T e remedy here was to use a larger fi nal aperture (150 to 200 µm) when needed and a video frame averager, which allowed video imaging with reduced


www.microscopy-today.com • 2017 January


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68