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Digital documentations of microscopic images are very important in routine examinations as well as in fields of research. In comparison with conventional analogues images, digital techniques have various specific advantages. Images are immediately seen on the camera display and poor images can be retaken immediately. The ISO speed level can be changed for each image according to the brightness of the specimen, in most cases up to ISO 400 when compact or bridge cameras are used and up to ISO 1600 or 3200 when a digital mirror reflex camera is available. In high ISO speed levels effects of noise in digital images are lower than effects of visible grain in analogue images. Some high end digital cameras can be used with a flash and off-camera shoe for high speed synchronisation up to 1/2000 or 1/ 4000 s in automatic TTL mode. Digital images can be optimized by post-processing with the help of standard image optimizing software. Thus, fundamental parameters which determine the image quality can be influenced (gradation, brightness, contrast, colour saturation, white balance, sharpness). Moreover, perturbing structures such as dust particles, artificial bubbles etc. can be removed by software based retouching. Digital images can directly be printed or integrated into other presentations or documents (e.g. scientific or medical letters). Moreover, they can be directly transferred to other addressees by the web. In special fields, e.g. histopathology, cytopathology, hematology, onkology and other medical areas, interesting findings can be directly discussed by long distance conferences based on telemedicine when digital images are available. Decades ago, manufacturers of light microscopes had already developed connection modules that allow their microscopes to be used with analog cameras for photomicrography. For digital cameras, similar modules have not yet been widely developed. For digital microphotographic documentations specialised microscopy cameras are predominantly available which are utilizable just for photomicrography. From an economic standpoint, consumer digital cameras are an attractive alternative solution for photomicrography as they are much cheaper and produced in high numbers. Moreover, high-end consumer digital cameras can produce high resolution images, similar to analogue or film images. However, not all digital cameras are suitable for photomicrography because of potential artifacts, vignetting effects, deficiencies of coverage or sharpness and several other reasons. Therefore, some technical solutions for digital photomicrography were elaborated that have been rigorously and successfully tested in practice, using several models of current digital cameras with various designs (compact, bridge or prosumer, and single-lens or mirror reflex). All aspects of mechanical and optical adaptation, exposure, manual focus, image control, potential artifacts, automatic and manual flash light control, monochrome techniques and other modes of light filtering based on various astronomic interference filters were evaluated using several suitable digital cameras. The qualities of the respective images were visually compared using high resolution monitor images and colour prints. In addition to this, several software-based methods in postprocessing were evaluated, including stacking and sandwich techniques. These evaluations lead to the result, that several digital cameras (compact, bridge, mirror reflex) show good qualities when used for photomicrography. Thus, such cameras can be regarded as practicable and attractive technical solutions, cheaper than specialized microscopy cameras and useful for other photographic purposes, too. The image quality is comparable with the quality of conventional analogue images taken on a 24 x 36 mm film when the CCD- or CMOS-sensor is at least 6 or 8 megapixels. When monochromatic green filters are used, the quality of monochrome digital images can be optimized furthermore. Especially contrast, sharpness and resolution can be improved because any chromatic aberration is eliminated. Several astronomic filters, especially contrast-booster filters and apochromatic filters work as RGB-intensifiers; by these filters, the primary colours (red, green, blue) are enhanced selectively. UV- and IR-cut filters and fringe killer filters can block ultraviolet and infrared or violet and short-wave blue radiation. By these means, the quality of colour images can be fundamentically improved; colour saturation, colour purity, contour sharpness and resolving power can be enhanced, visible in life microscopy as well as in photomicrography. Moreover, some modern digital compact cameras are suitable for video documentations of dynamic processes in microscopy.
Figure 1: Native epithelial cell, objective oil 100x, phase contrast,
Figure 2: Native epithelial cell, objective oil 100x, phase contrast,
Figure 3 and 4: Asteroid-arm, stereo-microscope, epi-illumination, objective 4x,
Figure 5: Comparison of several digital cameras, suitable for photomicrography
Figure 6: Bacillus megatherium, phase contrast, objective oil 100x, several green filter techniques
Figure 7: Software-based modification of the gradation histogram, small scratch on a polymer layer,
Publications: Piper, J.: Technical realisation of digital photomicrography using digital cameras for consumers Piper, J.: Technical realisation of digital photomicrography using digital cameras for consumers Piper, J.: Adapting consumer digital cameras for photomicrography: Piper, J.: Advanced techniques of software-based three-dimensional reconstructions and optimizations in sharpness of microscopic images (in German) Piper, J.: Benefit of astronomic filters in microscopy and photomicrography (in German) Piper, J.: Annular artifacts in mikroscopy and digital photomicrography Piper, J.: Use of astronomy filters in light microscopy and photomicrography Piper, J.: Software-based three dimensional reconstructions and enhancements of focal depth in microphotographic images Piper,
J.: Documentation of large-area specimens in
photomicrography - comparative tests of optical and
software-based methods (in German) Piper, J.: Wide field and deep focus
imaging in photomicrography - optical and
software-based techniques
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