Cultural Heritage FAQ's

Can I get a system today?
Systems are currently being configured for qualified users and will be available soon.  System purchase is not required to take advantage of the system.  Services to capture and assess images from a single document to a large collection are available. We would be happy to discuss your needs.

How large an image can be captured?
Three things limit the size of a scene (document) that can be captured in one frame:
1.  How much light is available.
2.  How many pixels are available.
3.  Optics, together with how much working distance is available.
Two light panels are enough to uniformly illuminate a scene of about 50cm X 60cm (18” X 24”).  If this scene is captured in one frame, the captured resolution will be about 12 pixels/mm (300 ppi).  Greater resolution may be achieved by imaging smaller segments and stitching segments together.   600 ppi is a practical resolution that may be achieved with excellent optical resolution at reasonable working distance; e.g., a 120mm macro lens will provide good 600 ppi images at about 1 meter working distance.
An optional motorized stepping table can be provided for conveniently moving large work pieces whose image segments which will be stitched together.

The EurekaVisionTM System provides a digital image frame size of about 40 megapixels. If 12 wavelength bands are captured for one frame, the entire uncompressed image is about 1 Gbyte in size.   While large, it is not too large to be captured, processed and analyzed efficiently on most recent computer systems. 

Talk about Calibration
Extensive component, system and image calibration distinguishes MegaVison systems.
Components are calibrated  and characterized  prior to system assembly.  During operation, pixel-by-pixel dark field, pixel-by-pixel white field, neutral balance, and color calibration are ongoing processes integrated with image capture. 

To obtain intensity and color uniformity over the scene, a diffuse uniform white reference target (such as scintered PTFE [Spectralon], barium sulphate paint, matt ceramic, or, less controlled but still useful, a high quality white paper) that covers the scene is recommended.  An image is captured of the white scene, and pixel-by-pixel gain adjustment is performed for each spectral band.  

For color validation, we encourage the use of a complete Macbeth target, sliced in strips and laid along the edge of every picture.  Macbeth makes small targets just right for this purpose. 

For calibration of neutral balance, we typically use an equal energy white such as is found on a Macbeth Color Checker target.  We expand our 3-color white balance and color calibration software (MegaVision pioneered the concept of white balance over 20 years ago) to encompass N-colors. 
PhotoShoot includes tools to facilitate measuring and adjusting  illumination uniformity over the scene. 

If budgets allow, additional calibration is possible.   For example, MegaVision’s aerial customers perform and exhaustive radiometric and geometric camera calibration...they actually map the warping of the sensor surface, calibrate the lens radiometric fall-off, and characterize its geometric distortion. It is possible to apply this process to the EurekaVision System.  This is an expensive option, but if the need arises, it is possible.
LED's are quite consistent, close to manufacturer specs, but there is measurable variation. We can certify all spectral bands of each light panel with a spectrophotometer.  This optional certification is available if the need arises.  Additionally, wavelength requirements can be specified by the user when ordering Eureka!Light™ illuminators.

How close is the EurekaVision System to being a spectrophotometer? 
A spectrophotometer can record response over a large number of narrow spectral bands.  However, a spectrophotometer evaluates only a single spot: i.e., 1 pixel resolution.   The EurekaVision System, on the other hand, evaluates millions of spots;  39 million for the E6.  But practical considerations limit the system to a dozen or so primary spectral bands.

Is there any method to verify that spectral bands are precisely the same bandwidth as last night or last week? 
Each panel is serialized and the serial # is read by PhotoShoot.  Calibration data is tied to Serial numbered panels, so calibration information for each panel may be tracked.  By taking pictures of an equal-energy white reflectance calibration target on regular occasion, calibration can be easily tracked.  Color calibration profiles for each illuminator-camera combination can be acquired and utilized for post-processing as well.

How did the system come to be?
The LED light technology was developed and used successfully on a high profile investigation of the Archimedes Palimpsest.   (To read about it, Google "The Archimedes Palimpsest", go to http://www.archimedespalimpsest.org, or  get the fascinating  book by Reviel Netz and Will Noel, The Archimedes Codex: How a Medieval Prayer Book Is Revealing the True Genius of Antiquity's Greatest Scientist).  A high resolution monochrome camera was not available at the time the Archimedes Palimpsest was imaged. 

When the MegaVision E6 monochrome back became available and was used together with the LED lighting for the Waldseemueller map project at the Library of Congress we knew the combination was extraordinarily good.  (Google "Waldseemueller map”, or visit the site: http://en.wikipedia.org/wiki/Waldseem%C3%BCller_map)

After scholars at Oxford University observed our application of these techniques during the Archimedes Palimpsest project and saw results from our LOC map studies, they recognized how well matched our system would be to their studies of ancient papyrus and papyrus objects. We obliged by providing a customized system for this long-term project.

Discuss the lighting setup
A light source perpendicular to scene on the optical axis will tend to eliminate surface texture and increase flare, especially from specular surfaces such as illuminated parchments, which often use gold foil. So 45º incidence is the recommended lighting angle.  We can also supply SideLong™ illuminators for “grazing” or  “raking” incidence illumination, in which light coming out almost parallel to the surface can enhance surface texture or depth variation of a surface. SideLong illuminators take the form of linear arrays of visible and/or IR LED’s approximately 2" X 2" X 18", with LED's along the long axis.

How does PhotoShoot control the lights?
While there will typically be two panels, one for the left side and one for the right side, PhotoShoot can control a great deal more.  Since PhotoShoot supports up to 16 serial-mapped USB ports, and typically only 2 other ports will be used for other purposes, support for up to 14 Panels is will be normally available.    Each Panel gets a port assigned by the host computer operating system or application.

PhotoShoot interrogates all ports, sends strings to the ports, evaluate the responses from the ports and attempt to recognize each devise based on the returned values from the strings sent.  The model, version and serial #”s are reported in the Camera Status window. If PhotoShoot is set to Scan on Startup, PhotoShoot will scan all  ports each time it launches, interrogate each port and enable recognized devices for use with PhotoShoot.  The user will recognize each light panel by its name and unique number reported by the Panel.

Since the each light panel has a unique identifier that is discovered upon polling by the PhotoShoot, a unique name can be affixed to the exterior of the light panel whereby the user can know which panel is being adjusted in software.

Should the user choose to add additional panels or unplug a panel (either intentionally or unintentionally) while PhotoShoot is running, a user can update port assignments from within PhotoShoot simply by pressing a button in the “Serial Status” tab in the Camera Information Dialog box accessed under the Setup/Capture/Camera Status pull-down menu. This will scan all ports and assign recognized devices for use.  The user need not be concerned with the ports to which the devices are attached, only with the unique identifiers of the recognized devices attached to the ports.

What controls are available for the light panels?
Basic controls via USB are in PhotoShoot: What spectral band on what panel turns on, when it turns on, and how long it stays on.   An exposure table, called the N-Shot table is created that defines all the lighting and shutter (and optional color wheel) actions that will occur during an N-shot capture.  “N” is the number of shots of a scene, typically 12 but can be more or less. Various tables may be created for various capture requirements.  Once a table is created, capturing an N-shot series is a simple matter of pressing PhotoShoot’s shutter release button.  Multiple shots are automatically captured, named, corrected and saved.  The lighting setup of each shot is automatically invoked.

Future versions will control power as well as duration. Illuminator firmware can be updated as new features are introduced.

Will each color be discrete or are mixtures possible?
Mixtures are possible in any combination.

Any effort to merge or join the data from light and X ray?
Many cultural and heritage artifacts are susceptible to X-ray damage; consequently, exposure levels must be carefully considered during x-ray transmission and fluorescence studies.  In order to exploit x-ray fluorescence (XRF) to detect metallic constituents of iron gall residues in the original inks of the Archimedes Palimpsest, for example, an intense x-ray beam at the Stanford Linear Accelerator Center was employed using a scanning beam technique.  This data could be registered at high resolution (40 µm per pixel) with the optical hyperspectral imagery, thereby increasing the dimensionality of the data space used to identify key content of the documents.   Such multimodal investigations are expensive and require considerable expertise to accomplish.  MegaVision can arrange on behalf of EurekaVision System customers for such investigations.  We work with experts in this field who can guide and assist the client through the process.

How about backlighting and opacity?
Backlighting is definitely used; correlating back-lit images with front-lit images gives more clues to what lies beneath (or within translucent materials).

Who would use a hyperspectral picture system?
Individuals and institutions responsible for reproduction, conservation, and preservation such as conservationists, archivists, museums, and libraries will find considerable use.  Additionally, collectors of valuable objects such philatelists and numismatists seeking  to assure value and provenance  of objects.

Do we have PCA or other quantitative postprocessing algorithms in Photoshoot? 
While the EurekaVision System approach was designed to provide images well-suited to sophisticated postprocessing techniques, we don't include such post-processing tools in PhotoShoot.  We are focused on capture-look-organize-save.  Our efforts are to provide images of sufficient quality, documentation and provenance to enable a wide range of post processing.  Our team can provide expert quantitative processing on a custom basis.

Explain a little about the camera itself
MegaVision has built lots of E6 backs with the 39megapixel CCD for other markets.  Most fly in airplanes and take geo-referenced pictures of stuff on the ground.  Some fly in tactical theater.

We do the dark and gain adjustments on the fly.  User doesn't need to get sullied.

Because the pixels are getting pretty small (6.8 microns on the 39megapixel E6), and because adjacent pixel response to light  is 100% (i.e, a pixel doesn't care what it's neighbor sees), and because there is no need to low-pass filter the light to reduce Bayer pattern under-sampling artifacts, the choice of lens is critical.  The camera is completely predicated on choice of lens.  The best lenses for typical EurekaVision System applications are available with copal mounts, so that means we need a camera which accepts a copal lens/shutter.  We built a USB interface to the Schneider digital shutter, which is a copal mount shutter that will accept copal-mount lenses and let us control the aperture and shutter speed from the computer.  The shutter is highly reliable with extremely low vibration so as not to contribute to shake and affect image registration.

We can mount the lens/shutter to any lens board on any view camera.  A unit like the Mamiya RZ or the Fuji GX 680 would work, since we usually don't need the swings and tilts of a view camera.  Unfortunately, such units don’t accept standard lens-board-mounting copal shutters and lenses.    View cameras and other technical cameras, such as the Toyo VX 23D and Linhof M679 with fine focus adjustments work well.

What about file formats?
There's only one kind of file that PhotoShoot recognizes: .DNG (Adobe's Raw "Digital Negative" file format).
Some professional cameras create out raw files in the form of DNG’.  Adobe makes translators for other proprietary raw formats (like Canon) to DNG.

It’s mostly just raw files that we shoot with our cameras...which PhotoShoot will develop into TIFF (8 or 16bits/color) or JPG, or export as raw DNG's to PhotoShop or other DNG compliant applications (which are growing in number). 

Developing a DNG file which is from a monochrome sensor is much different than developing a DNG file from a color sensor.  No interpolation is required for the monochrome sensor image, so the developed image retains the purity of the raw file.

Talk a little more about PhotoShoot.
PhotoShoot is just what its name implies; it's an application for capturing pictures.   PhotoShoot intimately couples with the camera and the lights to enable precise control of each.  PhotoShoot’s tool box enables optimization of the scene, light, lens, aperture, shutter, and digital back.  PhotoShoot controls the capture, references the image data to objective imaging standards, and enables rapid and convenient inspection of captured images to verify image quality.

Metadata in the header of the picture file facilitates organization, naming, and searching.

We adapt standard (IPTC and EXIF) metadata formats and optimize the fields where necessary to store all kinds of searchable information into the header of each file.  File naming and organization can be automatically determined by metadata. 

How can I be assured the system will work?
Only customers with appropriate requirements will be considered. A detailed assessment of a customer’s requirements will be made prior to configuring a system.  Installation and training will certify system performance and customer familiarity.

A full year warranty is provided and extended warranty is available.