MegaVision Archival and Cultural Heritage Imaging
Digital imaging’s impact on the guardians of our cultural heritage treasures is profound. Digital imaging has opened new avenues of research, offered new opportunities of service, and permanently altered perspectives on preservation and conservation. Digital imaging, while unquestionably nascent, offers such compelling promise that even in its infancy it is being widely deployed and is beginning to deliver on some of its promises. The many initiatives underway realize to varying degrees the promises; some would be well served with additional careful consideration of the goals. In a rush to deploy, the digital image data that is collected often leaves much to be desired. The EV™ system has been developed to provide digital imaging capabilities of sufficient integrity and scope as to more than satisfy a range of goals which other imaging technologies not only do not, but in large measure cannot, contemplate.
The EV™ system integrates two previously disparate imaging capabilities: High- resolution photography and multi-spectral imaging. It captures very high resolution, high dynamic range, and highly repeatable digital images over a range of 12 or more spectral bands from the near ultra-violet to the near infra-red. The spectral bands are created not by using band pass filters to filter the light after it is reflected from the treasured object, but by using narrow-band LED illumination which subjects the treasure to only the light energy that is required to expose a highly sensitive, unfiltered monochrome sensor. This strategy results in orders of magnitude reduction in the light energy to which the treasure is exposed, and provides images of unprecedented resolution, registration, quality, and spectral content. Because the capture process is highly repeatable and because the captured image metadata is replete with not only artifact and collection specific data but also with capture specific detail, the captured images are documentary milestones that will be used not only in current conservation, preservation, scholarly, and reproduction initiatives, but by those of future generations as well. The image datasets acquired by the EurekaVision™ technology become, in and of themselves, assets of scientific and historical value.
The EV™ multi-spectral imaging system is designed for preservation and scholarly studies of cultural objects, for studies of parchment, paper, papyrus, fabric, dyes, inks, paint, and other constituents of valuable objects, and for accurate color reproduction of cultural objects and art. The system includes an advanced large-format digital camera, a low-heat multi-spectral LED illumination system, operational software, and selected peripherals all operating as an efficient integrated system.
Digital Camera: MegaVision EV
The EV Camera, which includes MegaVision's Monochrome E7 50-megapixel back (other lower resolution digital backs are also available), computer controlled shutter, computer controlled aperture, custom hyperspectral lens (parfocal and responsive over the entire range of silicon sensitivity), and purpose-built technical camera body is at the heart of the EV multispectral system. Each element of the EV camera is designed to provide meticulous control and solve imaging problems encountered when imaging priceless objects of great importance over a large spectral range. Some key metrics of the EV camera performance:
Illumination: EV™ LED Illumination System
A revolutionary EV™ LED illumination system provides unprecedented opportunities in imaging and image quality. This system enables imaging in multiple distinct narrow spectral bands or combinations of spectral bands over a range of wavelengths from the near ultraviolet to the near infrared.
The lighting system is fully integrated with MegaVision’s Photoshoot™ software and typically include light emitting diodes (LED’s) with up to 13 specific wavelengths, including:
Choice of 2 different spectral bands for optional SideLong™ raking illuminators.
Advantages of LED illumination
Each light head is 19cm X 12cm X 5.2cm (7.4” X 4.7” X 2” ). The panels mount with standard professional light stand mounting studs. Inside each panel are modules that are configurable. Each panel may be configured to include up to 13 different spectral bands with a total power of about 240 Watts. For example, the panels may be configured with only 7 visible bands, or may additionally include several IR bands and a UV band. Custom configurations are available to satisfy specific customer requirements.
The panels are powered and controlled via a power pack with an integrated USB Hub. Up to 6 panels may be powered from a single power pack. A single USB cable from the power pack to the computer enables Photoshoot™ software to control multiple light panels. Panels may be tiled to form larger units. Photoshoot™ can simultaneously control up to 14 individual panels.
Software: MegaVision Photoshoot™
MegaVision's Photoshoot™ digital image capture software is a comprehensive capture program designed to work with MegaVision's line of digital camera backs. Photoshoot™ controls all aspects of image capture: shutter duration, aperture, light duration, light power, selected wavelength(s). Photoshoot™ transfers captured images in uncompressed raw format from the camera directly into computer memory at about 40 megapixels/second. A 12-band image capture typically requires less than one minute. Photoshoot™ immediately creates and places thumbnail previews into an "electronic proof sheet" on the computer monitor. Photoshoot™’s tools for measuring and setting exposure enable precise adjustment of illumination to guarantee the very highest image quality over the entire spectral range.
Photoshoot™ implements metadata support based upon EXIF and IPTC standards which may be customized to embed database information directly into the image files. Photoshoot™ enables automatic naming and organizing of captured images based on associated metadata.
Photoshoot™ software controls the EV LED panels and the digital shutter and aperture in an integrated fashion. Photoshoot™ also controls an optional color wheel should additional light modifications be desired (such as polarization or filtration to isolate fluorescence in concert with UV illumination).
Monochrome Image Capture
Color Capture With a Monochrome Sensor and LED Illumination
By coming at the problem from a different angle, namely, creating the color bands at the source of the light (using LED's), the EV™ system solves the intractable practical problems.
Capturing sufficient perfectly registered and highly repeatable spectral bands is an enabling technology for deploying semi-automated, high-quality color reproduction. With tri-stimulus capture, color matching over a practical range of commonly encountered dyes, pigments, plastics, and other materials is sufficiently poor that individual, scene-specific color adjustments must be performed to obtain the desired quality. This color-matching step is sufficiently time consuming and costly that it is practical to create high-quality color reproductions of only the most expensive originals. The EurekaVision™ approach can dramatically reduce the amount of labor intensive post-processing of the image data and provide highly accurate color reproduction of a very wide range of difficult subjects.
The EV system integrates two previously disparate imaging capabilities: High- resolution photography and multi-spectral imaging. It captures high resolution images over 12 or more spectral bands from the near UV to the near IR. The spectral bands are created not by using band pass filters to filter reflected light, but by using narrow-band LED illumination which subjects the treasure to only the light energy that is required to expose a highly sensitive monochrome sensor.
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