Abstract: A histogram preparing portion prepares a density histogram based on input image data. A reference value calculating and correcting portion calculates a white reference value and a black reference value for adjusting density on the basis of the density histogram. A reference value determining portion corrects one of the white reference value and the black reference value such that the black reference value is necessarily greater than the white reference value. An automatic density adjusting portion adjust the density of the input image data with the corrected white or black reference value. Thus, automatic adjustment for removing a background or darkening a light letter can be performed suitably without failure, so that a clear image can be provided.

Abstract: An image processing method includes inputting pixels into an input image data buffer. Each input pixel has an original value equal to one of n values representing n density levels. A first transforming step includes a defining step and a determining step. The defining step defines a pixel set including a plurality of non-processed pixels located adjacent to each other in a processed-pixel recording buffer. The determining step determines output pixel values from m values. Each of the output pixel values determined by the determining step is assigned to each non-processed pixel. A second transforming step transforms each of the input pixels to a transformed pixel which has an output pixel value equal to one of m values representing m density levels according to an error diffusion method. A selecting step selects one of resultant values produced by the first and second transforming steps in accordance with an original value of an input pixel currently being processed.

Abstract: A method and apparatus are provided for enhancing JPEG compressed digital image data wherein only the DC components of the compressed image data are required to obtain a statistical subsampling of the corresponding uncompressed image data. JPEG compressed image data are received that represent an input digital image, and the JPEG compressed image data include a plurality of DC components. DC components are extracted from the JPEG compressed image data, and the extracted plurality of said DC components represent a subsampling of the input digital image. At least some of the plurality of extracted DC components are input to an automated image enhancement system. The DC components input to the automated image enhancement system are used to derive at least one of a final correction tone reproduction curve and a sharpness filter for enhancement of the input digital image represented by the JPEG compressed data.

Abstract: In an image reading apparatus for reading an original image, an optimum charge storage time of a line image sensor (105) in generating shading correction data and an optimum charge storage time of the sensor in reading an original image using the generated data are stored in a storage time setting unit (103) in correspondence with each of the first reading mode in which the image of an original placed on an original table (201) is read while moving the sensor and the second reading mode in which the image of an original fed by an ADF one by one is read at a predetermined position while fixing the sensor at the position. To actually read an original image in the first or second reading mode, an optimum value is selected from the plurality of stored storage times and used.

Abstract: In a first image processing apparatus, a digital image signal representing an image before being subjected to shutting light processing, and an unsharp image signal representing an unsharp mask image used for shutting light processing are formed. The unsharp image signal is obtained from the digital image signal. Compression processing is performed on the digital image signal to form a compressed digital image signal. Compression processing is also performed on the unsharp image signal, thereby forming a compressed unsharp image signal. The compressed digital image and unsharp image signals are stored on a storage medium, and then delivered to a second image processing apparatus. In the second image processing apparatus, the compressed digital image and unsharp image signals are reproduced from the storage medium, and decompression processing is performed on the compressed digital image and unsharp image signals to obtain decompressed digital image and unsharp image signals.

Abstract: An image reader including an optical reading section that reads reflected light from a light source; a reference density member that is fixedly installed at an original document reading position, and that is read by the optical reading section for acquiring data for correcting the light amount of the light source; a correction coefficient setting section that sets a correction coefficient for every read page, based on reference data obtained by reading the reference density member in advance, and read data obtained by reading the reference density member during each time interval between two successive pages of the original documents fed to the original document reading position one page after another; and a light amount correction section that performs light amount correction according to the above-described correction coefficient corresponding a read page, for each of the pages of the original document images read by the optical reading section.

Abstract: During reading process, an image reading unit read a white pressing plate (reference member) under a state where no original exists between the white pressing plate and an original glass plate. On the basis of the read image data, it is judged whether dirt is detected on the glass plate or not. If dirt is detected, a page in which a black line appears is determined. Information of the page is displayed on a display section. An original of the page is reread by the image reading unit.

Abstract: There is described an image-reading apparatus, which reads an image residing on a document by controlling a main-scanning operation in response to an index period, a sub-scanning operation in response to a line-thinning rate and a reading velocity in a sub-scanning direction in response to a magnification factor for reading the image. The image-reading apparatus includes an inputting section to input the magnification factor, an index period changing section to change the index period, based on the magnification factor inputted by the inputting section, and a line-thinning rate changing section to change the line-thinning rate, based on the magnification factor inputted by the inputting section. The index period changing section selects a certain index period out of a plurality of various index periods, including at least a normal index period and a long index period, to change the index period.

Abstract: An image reading apparatus includes an imaging unit which has a plurality of channels and which, for the channels, outputs effective signals output from photo-receiving sections for receiving light from a subject, and optical black signals output from light-shielding sections in which the light from the subject is shielded. The image reading apparatus also includes a monitoring unit for monitoring the optical black signal output from the imaging unit, a correcting unit for performing shading correction on the signals output from the imaging unit, and a controller for controlling timing with which the shading correction by the correcting unit is performed. In an image reading method for the apparatus, the shading correction is performed in response to a job start signal, and based on an optical black signal monitored thereafter, the shading correction is performed again.

Abstract: A dual digitizer for digitizing both transparent and reflective data mediums is provided where light from the reflective illuminator reflects off the transparent illuminator when the transparent illuminator is off to provide a white reference signal for use in calibrating the dual digitizer. A method of calibrating a dual digitizer for reflective scans includes: digitizing a transparent data medium; calibrating the dual digitizer to establish a white reference signal, the calibrating step including generating a light beam, reflecting a first portion of the light beam off a transparent illuminator, and utilizing the first portion of said light beam to establish the white reference signal; and digitizing a reflective data medium. The dual digitizer may be used in medical applications to digitize a transparent data medium such as an X-ray film.

Abstract: A non-coplanar calibration system exists when the calibration reference plane is offset from a document plane. Due to size, shape, or other factors attributable to a scanning system, it may not be feasible to place the calibration reference plane on the document plane, i.e., the platen glass. Lamp-fall off represents an effect that occurs as you get closer to the ends of the lamp and light energy is diminished. The profile difference between the calibration plane and the document plane in a non-coplanar system can be corrected for on a pixel by pixel basis. Illumination fall off due to the change in the distance from calibration plane to the document plane represents the main effect that must be corrected for. Also, the platen glass must be taken into account. A single calibration correction factor can be applied to each CCD element in a scanning system to account for the shift from calibration plane to document plane.

Abstract: An image processing apparatus and an image scanning apparatus detect a position of an abnormal pixel caused by obstruction to reflected light from a manuscript due to dust and others and correct the abnormal pixel by using data of normal pixels surrounding the abnormal pixel on the basis of a result of the detection. Based on image data read from a null-image prior to optical reading of a manuscript, an abnormal pixel detecting part detects the position of the abnormal pixel caused by the dust and others lying on a contact glass equipped between the manuscript and a CCD. An abnormal pixel correcting part uses pixel information at the position of the abnormal pixel detected by the abnormal pixel detecting part to correct image data read from the manuscript.

Abstract: A sheet-through document reader for reading an image formed on a surface of a document original being transported through a reading position. The document reader includes: a reading mechanism for performing main scanning to scan the surface of the document original in a direction perpendicular to a document transport direction at the reading position thereby to read an optical image of the document original, and converting the optical image into image signals; an abnormal value detection circuit for determining whether or not any abnormal value is present in image signals obtained by performing the main scanning by means of the reading mechanism, for example, before the document is read; and a reading position shifting mechanism for shifting the reading position in the document transport direction when the abnormal value detection circuit detects an abnormal value.

Abstract: An image reading apparatus includes a light source, a white basis plate, a first white basis data acquisition device that acquires a white basis data W1 by reading the white basis plate, with the light source that is fully cooled on, and a second white basis data acquisition device that acquires a white basis data W2 by reading the white basis plate with the light source on just before starting to read a first page of a document. The image reading apparatus also includes a compensation data acquisition device that acquires a compensation data K, based on the white basis data W1 and the white basis data W2 and a shading compensation device that outputs compensation image data P2 by compensating for a shading effect of each page of an image data P1 that is acquired by reading each page of the document, based on black basis data B, the white basis data W1, and the compensation data K acquired in advance.

Abstract: An image forming apparatus with an image sensor for scanning a document to produce an electric signal; a converter for converting the electric signal into image data with a predetermined number of bits, m; a shading memory for storing output image data, scanned during a first mode operation with the converter, pixel by pixel, and also storing shading factors each corresponding to each pixel of the image data; a controller for reading the image data stored in the least significant address to the most significant address of the shading memory during the first mode of operation, finding shading factors for each pixel by dividing a preset maximum brightness value, M, by each of the sequentially read image data, then storing the shading factors in the shading memory, and for outputting the shading factors stored in the shading memory corresponding to each pixel of image data produced by the converter during a second mode of operation; a shading compensating circuit to multiply, pixel by pixel, the shading factors

Abstract: A white reference image is inputted to an image sensor with a light source lit up, and white reference data is set every effective photosensor element by inspecting the output signals of the image sensor as to the white reference image (steps S305 and S310). After the input of the white reference image, the light source is extinguished (point e in FIG. 1), a black reference image is inputted to the image sensor (step S315), and black reference data is set every effective photosensor element by inspecting the output signals of the image sensor as to the black reference image (step S320). After the light source is lit up (point f in FIG.

Abstract: An image reading apparatus is provided which includes a contact image sensor comprised of a plurality of sensor chips arranged in series, an analog image processor for processing an analog image signal from the contact image sensor, a unit for conducting black shading correction for each pixel and a unit for conducting white shading correction for each pixel. The image reading apparatus further includes a unit for digitally monitoring a black offset value corresponding to each chip with respect to the signal that has been processed by the analog image processor and a unit for adding and subtracting a black offset variation amount for each chip in the previous stage of the unit for conducting black shading correction for each pixel, and corrects black offset based on an instruction of a control unit.

Abstract: In an image reading apparatus according to the present invention, a black reference plate used for shading correction includes a light shielding plate. When the light shielding plate shields an optical path leading to a CCD sensor, the light emitted from an illumination device is prevented from falling on the CCD sensor.

Abstract: A gray scale scanning method and system. Three groups of gamma table data are downloaded into a color scanner. Each group of gamma tables includes a plurality of index addresses and each index address corresponds to a storage space. During downloading, the gray scale pixels are scanned to obtain corresponding digital data. The digital data includes the brightness value of the three primary colors belonging to each gray scale pixel. The brightness value of the three primary colors and corresponding index address of the three groups of gamma tables are compared to obtain an index address identical to the three primary color brightness values of the gray scale pixels. According to the three index addresses, color space conversion values belonging to the gray scale pixels are obtained. The values are transferred to the host for conducting two add operations so that the gray scale brightness values of the gray scale pixels are found.

Abstract: An image processing apparatus includes an image sensor formed from a plurality of areas each including a plurality of pixels, and a corrector adapted to correct signals from the plurality of areas of the image sensor. The corrector has a plurality of correction data smaller in number than the areas, and performs correction by selectively using the correction data for each area of the image sensor.

Abstract: An image reading apparatus, including an image sensor configured to receive light and output an image signal in accordance with image data carried in the light, an A/D converter configure to convert the image signal into a digital signal with reference to a reference voltage, and a reference white plate configured to be read so as to generate density data. Also included is a correction device configured to correct the digital signal in accordance with shading data, a reference member configured to define a readable density limit, and a detection device configured to detect a ratio of density of the reference white plate to that of the reference member as density adjustment data. The density is obtained by reading the respective reference member and reference white plate in substantially a same exposure condition. Further included is a control device configured to control the correction device to adjust the digital signal in accordance with the density adjustment data.

Abstract: An apparatus and method for correcting a scanning error in a flatbed scanner, can minimize the scanning error due to deviations in position or scanning of a CCD (charge-coupled device) module by determining a scanning position, a scan region, and a scan rate for each flatbed scanner. The scanning error correcting apparatus includes a white shading plate having a black patch, a reading module for reading the white shading plate and the black patch, and a controller that compares information about the black patch read by the reading module with a predetermined reference value to correct the scanning error in the flatbed scanner. Thus, the apparatus and method can secure a scanning region in horizontal and vertical directions as wide as possible for each flatbed scanner and prevent occurrences of errors in a scanned image due to deviations of the CCD module.

Abstract: An image reading apparatus comprises a correction coefficient determining circuit 4 for determining a correction coefficient per each bit of white reference data in a main scanning direction which are read immediately before reading an original image, a correction coefficient modifying circuit 5 for producing a modified correction coefficient, and a correction coefficient predicting circuit 6 for producing a predicted correction coefficient with reference to the modified correction coefficient. If an absolute value of a difference between the correction coefficient and the predicted correction coefficient is smaller than and not smaller than a predetermined threshold value, the correction coefficient modifying circuit 5 produces the correction coefficient and the predicted correction coefficient as the modified correction coefficient respectively. A correction coefficient memorizing circuit 7 memorizes the modified correction coefficient as shading correction coefficient data.

Abstract: These methods for correcting density characteristic and color store previously a reference measured value obtained by measuring a reference original with a reference measuring instrument, read the same reference original with an image reading apparatus which is a target to be corrected, compare an statistic obtained by analyzing the thus read value with the stored reference measured value and calculate at least one of an input density characteristic correction parameter and an input color correction parameter, based on the obtained result. As a result, these methods can suitably correct the unevenness of the various characteristics, the unevenness of the spectral sensitivity or both of the image reading apparatus (scanner) caused by light sources, optical filters, image sensors or the like and perform the correction of the density characteristic which is a basis of an appropriate color reproduction in accordance with the original image, the color correction for obtaining a constant color reproduction or both.

Abstract: A method for correcting for defects in a digital image taken by an image sensor when there are pre-existing defects in two pixels in adjacent columns of the image sensor which causes two adjacent lines of pixels in the digital image to have corrupted data.

Abstract: An apparatus for forming an image includes a photosensitive body, an optical write unit which scans a light beam along a main scan path on a photosensitive body to create a latent image thereon, the light beam having power levels corresponding to multi-level image data, and a shading correction unit which corrects shading along the main scan path by making adjustment to the multi-level image data along the main scan path, and changes the adjustment on a condition-specific basis.

Abstract: In a document reading apparatus having a scanning exposure reading system by which a document placed on a platen is scanning exposed by an optical system and a document image is read out, or a document reading system by which a moving document is read out by an optical system, at the first collection position and the second collection position which are different in the sub-scanning direction of the scanning expose on a reference density plate, the first shading correction data and the second shading correction data are respectively read in the main scanning direction, and the shading position is corrected on the basis of the read first and second shading correction data.

Abstract: An image reading apparatus is provided which is capable of determining an image reading start position without using expensive members such as photo sensors, nor needing positional adjustments. The image reading apparatus of the present invention sets a first carriage 21 at an image reading start position PS upon initialization thereof, carries out shading correction, sets again the first carriage 21 at the position PS, and reads, upon receipt of an image reading instruction, an image of a document placed on a document mounting glass plate 11 by means of the first carriage 21.

Abstract: An image processing circuit is provided in which a clock signal is divided according to bits of data input thereto and supply or interruption of the divided clock signals is controlled according to the value of the input data. Therefore, it becomes possible to interrupt the clock signal which is to be supplied for a bit among the bits of the input data which is not used for a long period of time and reduce the power consumption of the circuit.

Abstract: In a photographic film digital image scanner, long term adverse effects on image scanning system response are compensated for by establishing an initial gain calibration profile in advance of commencing image scanning operation. A reference Dmin value is established at the same time, preferably from film Dmin regions associated with the bar code pattern located in the leader portion of the film. When image scanning operation is commenced, an updated Dmin value is established for the frame being scanned and the initial gain calibration profile is adjusted by multiplying the pixel-by-pixel values in the profile by the ratio of the reference Dmin over the up-dated frame-specific Dmin value. Preferably, the same image sensor photosites used to establish the reference Dmin value are used for establishing the frame-specific Dmin value and the readings are taken from Dmin regions of the film associated the bar code pattern adjacent the frame to be scanned.

Abstract: In an image scanner, an optical image is formed on a CCD image sensor through a lens unit from rays traveling through a picture frame placed in a film carrier, so image signals are picked up from the picture frame. The image signals are corrected with shading correction data that are read out from a memory in accordance with the magnification of the lens unit. The memory previously stores shading correction data for frequently used magnification steps. Shading correction data for less frequently used magnification are previously stored in a hard disc. If the lens unit is set at a magnification for which the memory does not store suitable shading correction data, the suitable shading correction data are read out from the hard disc, and written on the memory.

Abstract: An apparatus for scanning a matter in a document scanner such as a facsimile machine, includes a passage through which said written or printed matter is transferred, a scanning plate with a reference scanning surface positioned over said passage means, and an adhesive scanning tape having a reference color adhered to said reference “scanning surface. The adhesive scanning tape is readily detachable from the screen scanning surface.

Abstract: An image processing apparatus and image processing method of the present invention are characterized in that, if a platen cover is opened, image data of a non-original region is erased from data obtained by reading the original, and thereafter density of the image data of the original is sensed and a histogram is made. Thereby, it is possible to avoid the situation wherein a bad influence such as unnatural density variation is caused to an output image.

Abstract: The present invention provides a transforming method for increasing bit number of digital image signals generated by a scanner. The scanner comprises a scanning module having a plurality of linearly arranged sensors for scanning a document and generating a plurality of corresponding analog image signals, an A/D (analog to digital) converter for converting each of the analog image signals into a digital image signal with a first bit number, and a white calibration area and a black calibration area for calibrating the scanning module.

Abstract: A a shading correction apparatus and method for an image scanning system are provided. The shading correction apparatus of an image scanning system includes: an analog/digital converter for converting the analog image signals into digital image data having a preset number of bits; a shading memory for storing a shading factor matrix prepared from a first shading reference pattern at the preset storage time; a time determination corrector for periodically generating correction determination data as shading data achieved from a second shading reference pattern to determine the correction time for optical parts, and informing whether deviation data between correction data at the present time and preset standard data is above a certain allowed value; and a shading corrector to perform shading correction on receipt of the output from the analog/digital converter using the shading factor matrix when the operation of the image scanning system is in a real scan mode.

Abstract: In a document handler associated with an input scanner, such as for a digital copier or facsimile machine, an image-bearing sheet is moved over a relatively narrow window, through which the image is recorded by a photosensitive chip. When a spot of dirt attaches to the window, a streak results in the image data. This streaking problem is addressed by detecting image data consistent with such a streak, and applying a suitable correction algorithm to the image data. The suitable algorithm is chosen based on the thickness of the streak and the nature of the image data.

Abstract: A method of calculating shading correction coefficients for an imaging system from a non-uniform and unknown calibration standard is disclosed. The standard may be of two or more dimensions and divided into several parts. The standard is imaged in an initial position to obtain a set of initial image intensities corresponding to defined regions on the standard. The standard is then repositioned and imaged in one additional re-arrangement for each of its dimensions. For each re-arrangement, an set of re-arranged image intensities are obtained. The initial and re-arranged image intensities are combined mathematically to determine a shading error for each of the defined regions, based on a value selected for one or more of the shading errors. The shading errors are inverted to provide a set of shading correction coefficients. Either of the shading errors or the shading correction coefficients may be normalized to eliminate the effect of the selected value.

Abstract: An image-reading device is provided. The image-reading device comprises a photoelectric converting element reading a first image from a subject copy, a reference-white member functioning as a reference white used in a white-shading correction, reading means for reading a second image from a constant range on a surface of the reference-white member by using the photoelectric converting element, averaging means for dividing image data of the second image into a plurality of blocks in a sub-scanning direction so that each of the blocks includes a plurality of lines and obtaining average values of image data of the lines in the blocks respectively, peak-value determining means for obtaining a peak value of the average values, and white-shading correcting means for performing the white-shading correction to image data of the first image by using the peak value as white-shading data.

Abstract: This invention causes an image which has been read out by a CCD sensor during a first scan to be converted into an electric signal corresponding to the density of the image. A CPU forms by calculation a graph of the magnitude of density and the frequency thereof, namely a density histogram based on the electric signal obtained by the conversion. The contrast of the image is calculated, based on the density of the blank base part and that of the image formed part of the image which are calculated from the density histogram. The CPU sets the adjustment width based on this contrast and calculates the luminous energy of a lamp being used during a main scan in accordance with the adjustment width so set and the value of density set by a setting key. Thus, the present invention infallibly allows perfect density adjustment in an image of any degree of contrast.

Abstract: Shading correction data used in an image reading apparatus for shading-correcting image data obtained by reading an original image by a line sensor is acquired. A defect position on a white reference plate and a defect correction coefficient for correcting shading correction data at this defect position are obtained, and the shading correction data at the defect position is corrected by using the defect correction coefficient. Shading correction is performed by using the corrected shading correction data.

Abstract: In an image scanning system which includes an image scanning apparatus for scanning an image using a solid-state image sensing element, and an image processing apparatus, the scanned image undergoes image correction. The image scanning apparatus informs the image processing apparatus of image scan characteristic data such as linearity characteristic data unique to itself. The image processing apparatus executes a correction process of an image scanned by the image scanning apparatus using the received image scan characteristic data.

Abstract: An image reading apparatus has an automatic document feeder and a flat bed, wherein a backing part which is read so as to ensure that a leading edge of an original is read is configured to have a white area and a gray area, either the white area or the gray area being read depending on a type of the original, and the original being read subsequently.

Abstract: An image reading apparatus includes a housing provided with a light passage, a transparent plate mounted on the housing, a light source for emitting light into the light passage, a lens array facing the image reading section on the transparent plate, a plurality of light-receiving elements arranged in an array extending in a primary scanning direction, and a light reflector formed on the transparent plate. The light reflector is offset from the image reading section in the secondary scanning direction, which is perpendicular to the primary scanning direction.

Abstract: A document reading apparatus that includes a white platen roller and image sensor positioned at an image reading portion of the apparatus. The white platen roller is used to provide white reference data used for shading correction when reading an original document. The image sensor selectively reads the white platen roller and outputs signal characteristic data after reading the white platen roller. The apparatus also includes a controller configured to control the reading of the white platen roller so that the image sensor reads the white platen roller a predetermined number of times. The controller also controls movement of the white platen roller so that a motor used to move the white platen roller is de-energized when the image sensor reads the white platen roller.

Abstract: An optical scanner and a method of operating an optical scanner comprising: a light source, a line detector detecting pixel intensity information, and a computer having a memory wherein the computer is capable of controlling the optical scanner such that the detected pixel intensity can be adjusted and wherein the memory holds a procedure comprising the steps of: initially generating line profile data comprising pixel intensity information by scanning a reference, initially generating first smoothed line profile data comprising pixel intensity information by scanning a background, whenever required generating second smoothed line profile data comprising pixel intensity information by scanning a background.

Abstract: In an image reading apparatus having a light source for illuminating a document, an image sensing element for outputting an electrical signal in accordance with an input light quantity, a first reference member, and a second reference member, shading correction data is acquired. A time since the light source is turned on is measured, and when the measured time does not reach a predetermined time, shading correction data is acquired by a first method using the first reference member. When the predetermined time has elapsed, shading correction data is acquired by a second method using the second reference member.

Abstract: In an image read apparatus which reads an image from a recording medium, such as a film, and outputs image data, and shading correction data is set. Time elapsed since the shading correction data is set is counted. Before performing main scanning, whether or not the elapsed time is longer than a predetermined period is determined, and if it is, the shading correction data is updated. The read image data is processed with shading correction using the shading correction data which is updated as time elapses.

Abstract: A color type determining device is made up of a difference detecting section, a density distribution determining section, a density distribution correcting section, a color line counter, and a color/monochrome determining section. In the difference detecting section, the color type determining device finds, from read data of an original read by a scanner section, a color density for each pixel. In the density distribution determining section, the color type determining device finds a color density distribution for each line, and, based on the color density distribution for each line, determines whether that line is a color line. In the color line counter, the color type determining device counts the total number of color lines, and in the color/monochrome determining section determines from the total number of color lines whether the original is a color original.

Abstract: An illuminating unit illuminates a plurality of different types of color original images. A line sensor reads each color original image and outputs an image signal. An AD-converting unit AD-converts the output image signal from the line sensor based on a reference voltage. A storage unit stores digital data corresponding to the reference voltage of the AD-converting unit. A converting unit converts the output from the AD-converting unit into an output voltage from the line sensor (CCD) based on the digital data. An operating unit performs at least one of a shading correction operation, a color conversion operation, and a gradation conversion operation based on the output from the converting unit. High-quality images are obtained regardless of the types of color originals by performing equal shading correction processes regardless of the types of color originals.

Abstract: Gain factors for correcting pixel to pixel variations in system response in a multi-pixel scanner array are determined by calculating gain factors for a so-called “open gate” condition (with no film present), by calculating gain factors for a so-called “Dmin” condition (looking at the minimum density of the film), and by selectively combining the “open gate” gains and “Dmin” gains to create composite set of gain factors which overcome the shortcomings of using either original set of gains alone. The composite gain factors can be a proportional sum of the two original sets of gains with the proportionality changing on a pixel-by-pixel basis to select more of one set of gains or the other set of gains. A number of discriminating functions are disclosed which may be used to calculate the proportionality based on some understanding of how the presence of film changes the characteristics of the scanning system.