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formatdepx stsdas.hst_calib.foc.focphot



formatdepx -- Create a FOC format-dependent nonuniformity image.


formatdepx input f3image output illumratio


A format-dependent nonuniformity (FDNU) image characterizes the differences in large-scale nonuniformity between images of different formats (i.e., differences in image size and offset, and whether the image has rectangular or square pixels). It is believed that this effect is wavelength independent.

The FDNU image for an image of a certain format is calculated by dividing that image by the corresponding section of a full photocathode image. The assumption is that illumination is uniform over scales of the reseau mismatch between the two images, so the ratio should be independent of wavelength and source non-uniformity. The full format image must be dezoomed if the input images have square pixels so that the large image is 1024 x 1024. If, however, the input image has rectangular pixels, the large image should be 512 x 1024 zoomed.

The quotient image may optionally be smoothed. If the input and output lists contain more than one name, then the smoothed and divided images are averaged to reduce the effect of photon statistics and other nonfixed noise contributions.


input [file name template]
The input files from which format-dependent nonuniformity images will be made. If more than one file name is passed to input, all files must be of the same format and have the same offset and pixel shape (rectangular or square).
f3image [file name template]
Full format photocathode images. If only one file name is passed to f3image, it will be divided into each of the input images. A list of files can be passed to f3image, in which case the files are paired with the input files; if there are more input files than f3image files, the f3image files are reused cyclically.

The full-format photocathode images should have the same pixel shape as the input files, either rectangular or square. The ratio of header parameters CD1_1 to CD2_2 is checked for each pair. Typically, the input and f3image files would be pairs at the same wavelength.

output [file name]
File name for the format-dependent nonuniformity image created by formatdepx.
illumratio = 1. [real]
The ratio of illumination levels in the large format image to those in the small format images; this ratio is assumed to be equal for all image pairs.
(smoothing = boxcar) [string, allowed values: boxcar | convolve |
median | mode | none]

The type of smoothing function to be applied to the quotient of the input and f3image images.

(xwindow = 13) [integer, min=1]
The X side of the box---in pixels---for smoothing.
(ywindow = 13) [integer, min=1]
The Y side of the box---in pixels---for smoothing.
(kernel) [string]
Kernel to be used if smoothing = convolve. This parameter is used only if smoothing = convolve. The kernel parameter will accept either the name of a text file containing the kernel, or the kernel elements themselves as a list of numbers. If a string of kernel elements is entered, the individual elements are separated by a comma or whitespace and rows are separated by semicolons; elements are assumed to be in row order. If kernel is a text file, however, the last row of the kernel is the first row of the text file.
(title = "format dependent non-uniformity") [string]
Title to be used on the output image.
(low_reject = 0.) [real]
Lower threshold for rejecting low-valued pixels when calculating the average; this threshold applies only when averaging images, not when calculating an average for smoothing. If low_reject is less than 1, it will be treated as a fraction of the total number of pixels that are to be ignored. If low_reject is greater than or equal to 1, then it will be treated as the number of low values that are to be ignored. For example, 'low_reject = 8.' will ignore the lowest 8 values, but low_reject = .8 will ignore the lowest 80% of the pixels.
(high_reject = 0.) [real]
Upper threshold for rejecting high-valued pixels when calculating the average. If high_reject is less than 1, it will be treated as a fraction of the total number of pixels that are to be ignored. If high_reject is greater than or equal to 1, then it will be treated as the number of high-valued pixels to be ignored.
(boundary = nearest) [string, allowed values: nearest | constant |

Type of boundary extension to be used.

(constant = 0.) [real]
Constant to be used if boundary = constant.
(zerodiv = 0.) [real]
Value to assign to the quotient in case of division by zero. See help for the images.imdivide task for more information.
(verbose = no) [boolean]
Display details of the operations on the terminal screen?
(inimglist) [structure]
This is a task-defined parameter---it cannot be changed by the user.
(f3imglist) [structure]
This is a task-defined parameter---it cannot be changed by the user.


1. Create a FDNU image using two small format images:

	fo> formatdepx im1,im2 f3im out 0.25



This task was written by David Giaretta.



Type "help focphot option=sys" for a higher-level description of the focphot package.

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