The ACT-1 software provides the capability to display the scale of a captured or live specimen image. Scale can be specified in terms of the objective lens magnification and the intermediate magnification, or by specifying the measured distance between two pixels in the image. In addition, a scale can be drawn onto the image in terms of the specified length of an individual pixel.

The scale annotation feature can be accessed by clicking on the scale button located in the main menu toolbar (Scale Annotation; Figure 1). In the Scale Dialog Box (Figure 2), the Live/Captured Image Selector determines which of the captured and live images will display the scale annotation. The Settings Set Name pull-down menu (Figure 2) can record up to eight different scale settings that are readily accessible.

To specify a new scale setting or to change an existing scale setting, select the desired setting name from the Settings Set Name pull-down menu. The name of a setting can be changed by clicking on the text box of the setting name and entering the desired name.

Next, the pixel resolution must be specified from among the options available, which include Optical, Measurement, Pixel, and None (Figure 2). The Optical option determines the scale as a function of the optical resolution of the objective lens and the intermediate magnification. The Measurement option determines the scale based upon a measured distance between two pixels in the digital image. The Pixel option uses the specified size of an individual pixel to calculate the scale. Finally, selecting the None option will turn off the display of the scale.

The display orientation of the scale annotation can be set to vertical or horizontal by using the Scale Direction feature. The Line Parameter Settings control the unit of length, the line width of the scale, and the number of sub-divisions included in the scale. Use the Color Settings features to change the color of the scale annotation and its background color.

Clicking the OK button in the scale dialog box will insert the scale annotation into the live or captured image. Figure 3 illustrates the result of displaying the scale on the live image window. Once the scale annotation is in place, the user may move the annotation to any position in the image by dragging with the mouse. When a captured image displaying the scale is saved to the host computer hard drive, the scale becomes permanent and can no longer be edited. One limitation of this feature is that the scale cannot be displayed for images that are opened from the File menu or from the Open button on the main menu toolbar.