Glossary Archives - Page 7 of 16 - book❷net book scanners

Light spectrum

Posted on 20. June 202220. June 2022 by Karin

The light spectrum is the visible range of the electromagnetic spectrum that can be perceived by the eye. The spectral range visible to humans is between 380 and 780 nanometers, corresponding to a frequency range of about 4·10¹⁴ to 7.5·10 14 Hz.

Each wavelength produces a different color, for example green has a wavelength of about 540nm and blue is between 450 and 500nm. If all visible wavelengths are displayed next to each other, a rainbow-like color gradient appears. In addition, there are wavelength ranges that the human eye cannot see or perceive because there is no trigger for a pulse. These ranges are called ultra-violet (10-380nm) and infrared radiation (>780nm). The shorter a wavelength is, the more energy it has. This is also the reason why ultraviolet light is so harmful for our skin and our eyes, because in the long run it stimulates molecules to change their spatial structure and to split off single atoms.

Noise

Posted on 20. June 20223. July 2023 by Karin

Data that obscures or corrupts signal, as that term is used in the expression signal-to-noise ratio. Although noise is generally unwanted and signal is wanted, there are exceptions. In some circumstances, for example, dithering, which produces noise, is deliberately employed to counteract the aliasing that results when certain frequencies in a sound or image interact with the sampling frequencies applied by digital-capture systems. While noise is often thought of as a random phenomenon, it may be either random or systematic (patterned).

NARA

Posted on 15. June 202215. June 2022 by Karin

The National Archives and Records Administration (NARA) is an independent agency of the United States government charged with the preservation and documentation of government and historical records. It is also tasked with increasing public access to those documents which make up the National Archive. NARA is officially responsible for maintaining and publishing the legally authentic and authoritative copies of acts of Congress, presidential directives, and federal regulations.

For internal use only, involving their own holdings or project with other partner organizations, NARA has developed Guidelines for Digitizing Archival Materials for Electronic Access which can be viewed on the NARA website.

ICC profile

Posted on 14. June 202218. October 2022 by Karin

What is an ICC color profile?

Your photo looks different on the monitor than on your smartphone or printout? Does this sound familiar? Just as every person perceives colors differently, every imaging device (monitor, scanner, digital camera) reproduces colors individually. This is called color space. Each color space has a defined range of colors that it can represent. This means that each input or output device speaks a different “language”, so to speak, when it comes to the colors it can display. In order for them to “speak the same language”, they must be calibrated and a color profile must be created.

To enable consistent color management between input and output devices in the digital workflow, the International Color Consortium (ICC) has developed an international standard format for color profiles. With the ICC color profile, a color image created with an input device (digital camera, scanner) can be reproduced in true color on a monitor or by a printer.

The first link in the process chain is the camera or scanner. Especially in digital preservation, it is particularly important to calibrate the camera or scanner using standardized color templates (e.g. X-Rite ColorChecker) and to create a corresponding color profile to ensure color-accurate reproduction.

True color straight from the camera

The book2net scanners and repro-systems are the only systems on the market equipped with a so-called true-color color management. Directly from the camera, it is possible to generate true-color images according to the color spaces sRGB, Adobe 1998 RGB, ECI RGB V1 and ECI RGB V2 and an ICC color profile. The corresponding ICC profile can be embedded in the image file. There is no need to use additional software such as Photoshop or Lightroom.

This makes it possible to meet all requirements of the digitization guidelines and standards without any problems.

The big advantage of book2net True Color Management: Unlike the creation of an ICC profile, which is calculated e.g. by means of a 24-bit color scan of an X-Rite Color Checker by a “calibration software”, the book2net True Color Management takes advantage of performing all calculations and adjustments in the internal imaging area of the camera with a color and analysis depth of 48 bits. Colors are hit even more precisely and noise is minimized.

The result: METAMORFOZE, FADGI and ISO/TS 19264-1:2017 compliant scan results!

ECI-RGB color space

Posted on 13. June 202214. June 2022 by Karin

Why using the ECI-RGB color space?

The ECI-RGB V2 color space is one of the standardized RGB color spaces.

It is the working color space recommended by the ECI (European Color Initiative) and the Metamorfoze Preservation Imaging Guidelines for professional image processing.

As a working color space for professional image processing ECI-RGB V2 covers practically all monitors/display technologies and the vast majority of printing systems/printing processes (without being unnecessarily too large).

At first glance, the largest possible RGB color space may seem ideal, since it covers all other color spaces. However, since many color values have to be truncated or interpreted during the computational conversion to much smaller color spaces, inaccuracies can slip in.

The corresponding ICC profile for integration in image processing programs can be downloaded free of charge from the ECI website and allows constant color reproduction on all output devices. ECI-RGB thus particularly fulfils the requirements for true color reproduction.

Color-accurate directly from the camera:

Thanks to the unique True Color Management of book2net scanners and repro systems, it is possible to create color-accurate scans directly from the camera in the color spaces sRGB, Adobe 1998 RGB, ECI-RGB V1 and ECI-RGB V2. Thus, all requirements of digitization guidelines, specifications and standards can be easily fulfilled.

The big advantage of the book2net True Color Management: In contrast to the production of an ICC profile, which is computed by a “calibration software” on the basis of a 24 bits color scan by a X-Rite Color Checker, the book2net True Color Management uses the advantage of all computations and adjustments in the own image area of the camera with a color depth and analysis depth of 48 bits. As a result, colors are captured even more accurately and signal noise is minimized.

Chromatic abberation

Posted on 17. November 202113. October 2022 by Karin

In optics, chromatatic aberration (also abbreviated to CA) is a failure of a lens that occurs when light of different wavelengths or colors is refracted to different extents. This can lead to lateral chromatic aberration, which manifests itself primarily at image edges in green and red or blue and yellow color fringes at light-dark transitions. Longitudinal color errors can also occur in the form of different discolorations in front of and behind the focal plane.

Comparison of an image without and with chromatic aberration, in this case a lateral chromatic aberration.

Source: Wikimedia Commons (unchanged)
Copyright: Creative Commons Attribution-Share Alike 3.0 Unported.

Since such color errors should be avoided when digitizing, our systems work with a chromatic-corrected lens that compensates for this phenomenon. Otherwise, colored fragments would show around the edges of black letters, for example, and the scan would not be identical with the original.

RGB color space

Posted on 16. November 202115. June 2022 by Karin

What is a color space?

Most likely you are reading this article on the screen of your computer, laptop or your smartphone. Do you see the colors in the illustrations? These colors are defined on your screen by the use of a color space. A color space is a defined range of colors. Color space means the use of a specific color model. A color model is a method of generating many colors from a defined group of primary colors. Each color model has a range of colors that it can generate. This area is the color space. The most common systems are RGB and CMYK.

When choosing which color space to use, the basic question is: Are you working in digital or print format? Digital devices such as cameras and monitors use a color space called RGB.

The RGB color space is composed of three basic colors to which the light-sensitive cones in the human eye react most sensitively: red, green and blue. Theoretically it is possible to decompose every visible color into combinations of these three “primary colors.” Color monitors, for instance, can display millions of colors simply by mixing different intensities of red, green and blue. It is most common to place the range of intensity for each color on a scale from 0 to 255 (one byte). The range of intensity is also known as the “color depth”. Multiplying all available color gradations per channel results in 2563 or 16,777,216 color combinations. One often finds the statement: 16.7 million colors.

The possibilities for mixing the three primary colors together can be represented as a three-dimensional coordinate plane with the values for R (red), G (green) and B (blue) on each axis. This coordinate plane results a cube called the RGB color space.

Source: Wikimedia Commmons Copyright: GNU-Lizenz für freie Dokumentation.

The RGB color space is based on colored light. The three colors of light combine in different ways to create color. It is an additive process, a look at the pictures shows why:

If all three color channels are set to their maximum values (255 at a one byte color depth), the resulting color is white.

If all three color channels have a value of zero, it means that no light is emitted and the resulting color is black (on a monitor, for example, it cannot be blacker than the surface of the monitor producing 0 light).

This type of color mixing is also called “additive color mixing”.

What types of RGB color spaces are existing?

Source: Wikimedia Commons (unbearbeitet)
Copyright: Creative Commons Attribution-Share Alike 3.0 Unported

Different color spaces allow for you to use a broader or narrower range of those 16.7 million colors used in an image. If you think about it, there is a nearly infinite number of ways you can mix different colors together. If you add just a little more green here or there, you have got a new color. Take away a bit more red, and you have just created yet another color. What most people do not know is that they can choose the level of color detail their camera records. A bigger color space captures more colors than a smaller one.

Color spaces differ in the number of colors that can be visualized within a color space. When it comes to working with digital devices, sRGB, AdobeRGB and ECI-RGB are among the most important and well-known color spaces:

The smallest of these color spaces, is sRGB. The sRGB color space was originally developed as a color space for CRT monitors in order to display images created in sRGB as similarly as possible on all monitors.

AdobeRGB is able to represent about 35% more color ranges than sRGB is able to. The color gamut was primarily improved in the green tones, including the blue-green area, i.e. the so-called cyan tones.

The ECI-RGB V2 color space is one of the standardised RGB colour spaces. It is the recommended color space in the Metamorfoze Preservation Imaging Guidelines and the only one allowed at the highest level of these imaging standards. As a working colour space for professional image processing ECI-RGB V2 covers practically all printing processes as well as all widespread display technologies. ECI-RGB thus particularly fulfils the requirements for true colour reproduction. A corresponding ICC profile for integration in image processing programs can be downloaded free of charge from the ECI website and allows constant colour reproduction on all output devices.

Exposure time

Posted on 11. November 202115. June 2022 by Karin

When scanning, the exposure time determines the length of time light falls on the sensor. If all other parameters remain constant, the picture becomes brighter with increasing exposure time. In inexpensive cameras, the exposure time is regulated by a mechanical shutter and it is set how long the shutter stays open to let the light through when taking the picture. The shutter then closes and no further information reaches the sensor.

In contrast, in our systems, we are using our X71 camera, which works with an electronic shutter. The 71 megapixel camera was especially designed for demanding continuous use in the digitization sector, providing a long service life. Therefore, the camera does not work with a mechanical fastener that is susceptible to wear. In order to regulate the time in which the sensor receives information, the sensor is electronically darkened and hence completely motion-free. This guarantees constant and reproducible exposure times even with high-volume digitization projects. The use of highly sensitive area sensors also reduces the duration of the necessary exposure time and, as a result, the scan time, thus supporting the most gentle and productive scanning.

The exposure time can also be individually regulated using our Easy Scan scanning software, which is very helpful, for example, when digitizing transparencies. Due to the changing film and transparency templates, it may be necessary to adjust the exposure time individually in order to obtain optimal results, regardless of the film density, material or pigment type.

Distortion

Posted on 11. November 202115. June 2022 by Karin

When digitizing, one speaks of distortion whenever the geometry of the original is not reproduced true to the original. The most common templates for scanning are documents, books, files or single pages. These usually consist of right-angled pages, the exactness of which should of course be maintained during the digitization process. However, depending on the optics used, it can happen that an actually rectangular A4 page looks, for example, “bulbous” or “pillow-shaped” in the scan. The edges and angles are then no longer straight and right-angled, but rather curved, too pointed or too blunt.

For this reason, it is imperative to use high-quality lenses for digitization that counteract this effect. In our scanning systems, the lens and sensor are matched to one another in such a way that a distortion-free capturing is guaranteed and no subsequent image processing or correction calculations are carried out using software.

Vignetting

Posted on 11. November 202115. June 2022 by Karin

In photographic technology, optical vignetting (edge decoration) is an effect that may be wanted in artistic photography, but is not desired when digitizing documents, which require a true-to-original capturing. Vignetting is essentially a decrease in brightness towards the edge area of the image, which is caused by the light guidance through the objective and the axially arranged openings connected to it.

The resulting images are significantly darker due to the drop in light from the edge and mostly the “lighter” center of the image is shown in a circle.

In order to avoid this effect with our scanners, we work with special lenses in which this effect has already been corrected, unlike conventional camera lenses. Subsequent image manipulation or correction using software is therefore not necessary.

Vignetting

When taking a picture with a microscope through the eyepiece. This photo was taken “freehand” with a compact camera above the microscope eyepiece.
Due to lack of optical adjustment, the edge of the camera sensor cannot be exposed.

Source: Wikipedia Commons (unchanged) Copyright: Creative Commons Attribution-Share Alike 3.0 Unported

Related Topics

Related Topics

Related Topics

Related Topics

Related Topics

Related Topics

Related Topics

Related Topics

Related Topics

Vignetting

Related Topics