Film scanner
Encyclopedia
Scan
Scan may refer to:Acronyms:*Schedules for Clinical Assessment in Neuropsychiatry , a psychiatric diagnostic tool developed by WHO*Shared Check Authorization Network , a database of bad check writers and collection agency for bad checks...
ning photographic film
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...
directly into a computer without the use of any intermediate printmaking. It provides several benefits over using a flatbed scanner to scan in a print of any size: the photographer has direct control over cropping and aspect ratio from the original, unmolested image on film; and many film scanners have special software or hardware
Hardware
Hardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....
that removes scratch
Scratch
Scratch may refer to:* A mark or indentation on a surface: Abrasion It may also refer to:- Recordings :* Scratch , by Kaela Kimura* Scratch , the soundtrack to the 2001 documentary Scratch...
es and film grain
Film grain
Film grain or granularity is the random optical texture of processed photographic film due to the presence of small particles of a metallic silver, or dye clouds, developed from silver halide that have received enough photons. While film grain is a function of such particles it is not the same...
and improves color
Color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...
reproduction from film.
Film scanners can accept either strips of 35 mm or 120
120 film
120 is a film format for still photography introduced by Kodak for their Brownie No. 2 in 1901. It was originally intended for amateur photography but was later superseded in this role by 135 film...
film, or individual slide
Transparency (photography)
In photography, a reversal film is a type of photographic film that produces a positive image on a transparent base. Also known as dias or slide. The film is processed to produce transparencies or diapositives instead of negatives and prints...
s. Low-end scanners typically only take 35mm film strips, while medium- and high-end film scanners often have interchangeable film loaders. This allows the one scanning platform to be used for different sizes and packaging. For example, some allow microscope slide
Microscope slide
A microscope slide is a thin flat piece of glass, typically 75 by 25 mm and about 1 mm thick, used to hold objects for examination under a microscope. Typically the object is placed or secured on the slide, and then both are inserted together in the microscope for viewing...
s to be loaded for scanning, while mechanised slide loaders allow many individual slides to be batch scanned unattended.
Dust and scratches
Dust and scratches on the film can be a big problem for scanning. Because of their reduced size (compared to prints) the scanners are capable of resolutions much higher than a regular flatbed scanner; typically at least 2000 samples per inch (spi), up to 4000 spi or more. At these resolutions dust and scratches take on gigantic proportions. Even small specks of dust, invisible to the naked eye, can obscure a cluster of several pixels. For this reason, techniques have been developed to remove their appearance from a scan, see film restoration.The simplest is the median filter
Median filter
In signal processing, it is often desirable to be able to perform some kind of noise reduction on an image or signal. The median filter is a nonlinear digital filtering technique, often used to remove noise. Such noise reduction is a typical pre-processing step to improve the results of later...
, often called despeckle in many graphic manipulation programs, e.g. in Adobe Photoshop
Adobe Photoshop
Adobe Photoshop is a graphics editing program developed and published by Adobe Systems Incorporated.Adobe's 2003 "Creative Suite" rebranding led to Adobe Photoshop 8's renaming to Adobe Photoshop CS. Thus, Adobe Photoshop CS5 is the 12th major release of Adobe Photoshop...
and the GIMP
GIMP
GIMP is a free software raster graphics editor. It is primarily employed as an image retouching and editing tool and is freely available in versions tailored for most popular operating systems including Microsoft Windows, Apple Mac OS X, and Linux.In addition to detailed image retouching and...
. It works by examining a pixel in relation to the pixels surrounding it; if it is too different from the surrounding pixels then it is replaced with one set to their median
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
value. This and other methods can be quite effective, but have the disadvantage that the filter cannot know what actually is dust or noise. It will also obliterate fine detail in the scan.
Infrared cleaning
Infrared cleaning works by collecting an infraredInfrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
channel from the scan at the same time as the visible colour channels (red, green, and blue). This is done by using a light source that also produces infrared radiation, and having a fourth row of sensors on the linear CCD
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
sensor. Photographic film is mostly transparent to infrared radiation (no matter what the visible image contains) but dust and scratches aren't, so they show up in the IR channel. This information can then be used to automatically remove the appearance of dust and scratches in the visible channels and replace them with something similar to their surroundings. A major limitation of this technique is that it can only be used on dye-based (color and chromogenic black-and-white) films; the image-forming silver particles in most black-and-white film stocks are opaque to infrared radiation.
Scanner manufacturers usually have their own name attached to this technique. Kodak developed Digital ICE
Digital ICE
Digital Image Correction and Enhancement is a set of technologies related to producing an altered image in a variety of frequency spectra. The objective of these technologies is to render an image more usable by Fourier or other filtering techniques...
at their Austin development centre, and is licensed by Epson, Nikon
Nikon
, also known as just Nikon, is a multinational corporation headquartered in Tokyo, Japan, specializing in optics and imaging. Its products include cameras, binoculars, microscopes, measurement instruments, and the steppers used in the photolithography steps of semiconductor fabrication, of which...
, Microtek
Microtek
Microtek International Inc. is a Taiwan-based manufacturer of digital imaging products and other consumer electronics. Among its current product line are Microtek branded plasma and LCD TVs, LCD flat panel monitors, LCD and DLP projectors, and digital cameras as well as their flagship line of...
and some others. Canon
Canon Inc.
is a Japanese multinational corporation that specialises in the manufacture of imaging and optical products, including cameras, camcorders, photocopiers, steppers and computer printers. Its headquarters are located in Ōta, Tokyo, Japan.-Origins:...
developed its own FARE (Film Automatic Retouching and Enhancement) system. LaserSoft Imaging
LaserSoft Imaging
LaserSoft Imaging AG is a software developer designing software such as SilverFast for scanners and digital cameras. The company's headquarters are located in Kiel, Germany, north of Hamburg, and another office in Sarasota, Florida, United States....
is developing the iSRD Dust and Scratch Removal, on which among others Plustek
Plustek
Plustek is a computer hardware company established in 1986 that manufactures image scanners. They have the MobileOffice, SmartOffice, OpticBook, OpticPro, OpticFilm, and OpticSlim line of products.- Competitors :*Canon*Epson*Fujitsu*HP*Lexmark*Microtek...
is relying.