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Trace: Resolution


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If by some reason horizontal or vertical scale of the image is misrepresented, you are able to correct it. Use menu command ViewResolution to do it. It is availiable if a surface image, curve, section, or histogram is active.

If you use Resolution… command to work with a surface image without any distances or sections plotted, the following dialog box will appear:

You can specify new vertical and horizontal units using Units fields. The maximum height difference on the surface may be corrected in the Size Z field.

Let us show in more details what is meant by Bit size field. In Femtoscan RAW-data files (*.spm) Z values are kept as short integers (short int = 2 bytes = 16 bits). Embeaded coefficients are used to convert this integers into real height values. If you open a file of a different format, containing height or some other information (intensity, for example) in different state, Femtoscan will transform it to the standart two-bytes format automaticaly. The height corresponding to one bit may be corrected in Bit size field.

Image sizes in XY plane may be changed in Size X and Size Y fields. If an option Constant proportions is selected, then X-Y proportions will be constant, otherwise you will be able to change them independently. If an option Apply to all images in the document is selected, then the same scale will be set for all subimages, otherwise all changes will affect an active image only.

Other fields in the dialog box become availiable when a segment is plotted on the image, or when the command Resolution… is run for section, curve or histogram.

A typical use of Resolution… function is the scaling of images obtained by electron microscopy. They are usually written in *.tif format and contain a measuring scale:

When you Open a TEM image in Femtoscan its color shows the intensity in RGB units, and its X-Y scale is usually misrepresented. Select the scale bar (or any other known distance) with the linear tool, call the menu function Resolution… and set the correct values in Distance and Units fields (100 nm in our example):

After this operation it will be possible to measure distances in XY plane correctly.

The same dialog window will appear if you call Resolution… function for a section or for a histogram. In this case the field Height shows the height difference between vertical marks on the section profile or on the histogram. Similarly the Distance field shows the distance between vertical marks in XY plane, and Dx and Dy fields show X and Y proections of this distance.

If you want to change XY scale only (or vertical scale only), leave label Z (or XY) unmarked to avoid the automatic change of resolution in the second direction.