Glossary of Terms
To convert data (microfilm, fiche, books, newspapers, etc.) to a digital form for use on a computer.
To cut off or remove the borders of an image. Scanners usually capture the area (dead space) around the target image. Cropping is the act of removing this unwanted data to a specific margin.
The act of rotating an image to compensate for off balanced or crooked images. The end goal is to make the image edges parallel with the edges of the materials in the image.
The act of removing noise (grainy dots throughout an image) through smoothing the image without blurring the edges. It is a filtering process that detects areas with noise and ignores complex smooth areas.
An adjustment to the intensity (brightness) of an image in order to match the output more closely to the original image. Gamma is the relationship between the density of the film image versus the film’s exposure to light. Gamma correction allows us to adjust the scanned images’ contrast for a variety of applications: to produce more natural-looking images, to “lift” or enhance text on dark film to make it more readable, to compensate for under- or over-exposure, etc.
When scanning bound works, a natural distortion appears from the curve of the pages into the binding. Curvature Correction is a software that allows us to flatten an image and remove that curve. The end result will create a rectangular image with straight text.
In production scanning, the operator may need to use a finger to hold down a page or document. Finger Masking software will detect the finger and remove it from the image so that it appears a finger was never in the original image.
(Optical Character Recognition) The process by which a scanned document is electronically analyzed, so that the text information can be extracted from the image and reproduced as a text file. Text generated by OCR is often input into text search databases, allowing retrieval of the original scanned image based on its content. This text information can also be embedded in your PDF or Word file to make these documents fully searchable as if they were pure text files.
The ratio between the size of the original document and the size at which it appears on your rollfilm. For example, an 8.5″ x 11″ document filmed at a 25x reduction ratio will appear as a 0.34″ x 0.44″ frame on the microfilm. It is helpful for the scanner operator to know the reduction ratio of the documents on the rollfilm as it makes setup time much faster.
Images on film can be placed sideways or upside down. Rotation is the act of turning the image 90°, 180°, or 270° so that the image can be easily viewed and read.
This is a filter that will increase the sharpness of microfilmed images. Images that were originally filmed out of focus can be blurry or fuzzy. With proper use of a sharpen filter, the readability of text can increase. However, care must be used when using sharpen filters as too much of the effect can produce unwanted, exaggerated edges or “halos.”
(Charged Coupled Device) are sensors used in digital scanners or cameras to capture the images. The CCD captures light and converts it to digital data that is recorded by the camera. For this reason, a CCD is often considered the digital version of film.
(Pixels per Inch or Dots per Inch) is a measurement of resolution in a digital image. You can determine the true resolution of an image by dividing the image size in pixels by the size of the document.
The amount of pixels in an image that are captured during the scanning process. Images that are captured at a higher resolution will contain more data and use more disc space, but not necessarily produce a better image. Ideal resolution will depend on a particular project and the images are intended to be used. 300 dpi is the minimum resolution for OCR, 200 dpi is usually ideal for web presentation, 300+ is typically used as an archival standard.
To put it simply, Interpolation is the use of software or hardware to scale the resolution of an image up or down. This is not the ideal technique as the software is adding or removing pixels to meet the desired resolution. Generally scaling down is acceptable, scale up is frowned upon. Image Retrieval only uses true optical capture for all of their imaging work.
In micrographics, duplex refers to film that contains two images within one frame. Usually stacked one on top of the other, a duplex roll will contain twice as many images as a regular roll.
In micrographics this refers to film that contains a single image within one frame.
In micrographics terms this describes one image below the other when film is held vertically. This may also be called landscape.
In micrographics terms this describes images next to each other if the film is held horizontally. This may also be called portrait mode.
In micrographics terms this describes the small marks on the edge of the film that indicates a frame or image. Blips come in 3 sizes; large, medium, small, and by default a fourth when none is present. The blip sizes normally indicate small page, medium-document and large-folder.
In micrographics terms this indicates the polarity of film. Negative film is black with white letters on the documents. When scanning microfilm this is the film poliarity of choice.
In micrographics terms this is the reverse of negative film and has white document and black letters. Although a microfilm scanner can scan positive film, the image quality is normally less than that of negative film.
Any adjustments that will be made to an image after the scanning process. This includes but is not limited to cropping, curvature correction, deskew, despeckle, OCR, file compression, and finger masking.
A file created as a secondary source to the master file. Many times, projects will require a TIFF master file and a derivative file such as .JPG, .PDF, .GIF, etc. IIRI will work with you to provide you all file types that are needed for your project.
Most images are captured as individual files and therefore need to be opened separately for viewing. A multi-page document is combining multiple images into one file. This is most commonly seen as a multi-page PDF or TIFF. Multi-page documents allow for easier viewing and searching for particular text over a number of different documents.
JPEG (Joint Photographic Experts Group) compression is superior to other formats such as GIF for reproducing full-color and greyscale images, but JPEG is still a 'lossy' form of compression, meaning that parts of the image are discarded in the process of converting it to a JPEG file. Conservative levels of JPEG compression can have negligible impact on the resulting image as far as the human eye is concerned, and still reduce the file to a fraction of its original size. At higher levels of compression however image blurring and 'artifacts' can appear, though this is the compromise necessary to achieve very small file sizes.
PDF is a file format developed by Adobe to allow documents to be viewed regardless of the original software, hardware, or operating system which the document was created on. This makes PDF a truly portable format, and as such it has become the de facto standard for the exchange of electronic documentation. Adobe makes their Acrobat Reader package freely available for download here.
TIFF (Tagged Image File Format) is a flexible standard that it is widely supported by many image processing applications. We use TIFF for black & white images as the TIFF compression algorithm used is best suited to this application. JPEG on the other hand is used for its ability to compress color image file sizes.