Scanning



Scanning


Resolution:

Optical resolution: the maximum number of samples the scanner takes per inch.

Interpolated resolution: the increasing of samples through mathmatical relationship of the actual samples: (nearest neighbor, bilinear, bicubic*)

Bit Depth and Dynamic Range:

Bit Depth is one measurement of the number of tones a scanner can differentiate; the depth is a measure of how many colors can be represented in each sample captured by the scanner.

Dynamic Range expresses how broad a range of tonal values a scanner can capture; this is similar to the photographic measure of density. And tonal sensitivity describes how well tones are differentiated.

Scanner Types:

    Flatbed Scanner
    Film Scanner
    Drum Scanner
    Sheetfed Scanner
    Video
    Digital Cameras (linear array, area array)

BitMaps:

All scans are bitmaps. A "bit" is just the tiniest unit of computer storage, representing either a one or a zero. A "map" is jargon for a table, like a spreadsheet - the information is organized two-dimensionally, into rows and columns. A bitmap is a table that describes where bits are located - as in an image.

Characteristics of Bitmapped graphics:

    Dimension: rectangular grids - number of pixels.
    Resolution: the number of samples (or squares in the grid) in each unit of measurement.
    Bit Depth: number of bits used to describe each sample. (1,8,24, etc)
    Color Model: number of channels for bits. (RGB, CMYK, Index)

Figuring File Size:



Sampling Errors:

Morie Patterns: A murky herringbone or crosshatched or dotted pattern in your scanned images from printed material. Moire patterns are caused by interference between two sets of fine pattern grids, the scanner samples and the halftone screen in the original image. The solution is to account for the line screen in the printed material.

Newton Rings: Interference patterns resulting from the contact of film stock and glass. These are most commonly seen on drum scanners, where the film is taped up against ta cylinder, but high resolution flatbeds can demonstrate the same problem. Usually occurs at very high resolutions. The solution is to use a special mounting oil.