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<strong>Imatest</strong> <strong>Documentation</strong><br />

Plot distortion figure selects the main distortion figure.<br />

The Plot intersection points and Detect points outside crop checkboxes are described below. If the first of them is checked,<br />

another figure is produced. They only work with the Grid pattern.<br />

Plot radius correction is described below.<br />

Display corrected image creates an additional figure with the corrected image calculated with the algorithm selected in<br />

Calculate line display using, above. It is most valuable for highly distorted lenses where the input image has been<br />

cropped. Choices are never, crop only (the default), and always. An example is shown below in the section on Severe<br />

distortion.<br />

Click OK . The calculations are performed, and the results figure(s) described in Results appears. You can zoom in by clicking on (and<br />

highlighting) the magnifier icon , then clicking on portions of the image of interest, as shown below. The detected points on the image<br />

are shown as red squares. The straightened line is drawn in magenta. Double-clicking restores the entire image.<br />

An enlarged portion of the results figure.<br />

When the calculations are complete the Save dialog box appears. The<br />

default directory is subdirectory Results in the data file directory. You can<br />

change to another existing directory, but new results directories must be<br />

created outside of <strong>Imatest</strong>— using a utility such as Windows Explorer. (This<br />

is a limitation of this version of Matlab.) The selections are saved between<br />

runs. You can examine the output figures before you check or uncheck the<br />

boxes. Select the items you wish to save, then click Yes or No . File names<br />

(where filename is the input file name):<br />

[filename]_distortion.png<br />

[filename]_corrected.png (only if displayed)<br />

[filename]_intersections.png<br />

[filename]_radius_corr.png<br />

[filename]_summary.csv<br />

[filename].xml<br />

The root file name ([filename], above) defaults to the image file name, but<br />

can be changed using the Results root file name box. Be sure to press enter.<br />

Checking Close figures after save is recommended for preventing a buildup<br />

of figures (which slows down most systems) in batch runs.<br />

The CSV and XML files contain EXIF data, which is image file metadata<br />

that contains important camera, lens, and exposure settings. By default, Save results dialog box<br />

<strong>Imatest</strong> uses a small program, jhead.exe, which works only with JPEG files,<br />

to read EXIF data. To read detailed EXIF data from all image file formats, we recommend downloading, installing, and selecting<br />

Phil Harvey's ExifTool, as described here.<br />

Results<br />

Main figure<br />

An example of Distortion output is shown below for the Sigma 18-125 mm f/3.5-5.6 DC lens (designed for APS-C-sized<br />

sensors, such as the Canon EOS-10D, 20D, Digital Rebel, Nikon D100, D70, etc. The Sigma is an excellent lens — a bargain —<br />

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