About measurement (Photoshop Extended)
Using the Photoshop Extended Measurement feature you can measure any area defined with the Ruler tool or with a selection tool, including irregular areas selected with the lasso, quick select, or magic wand tools. You can also compute the height, width, area, and perimeter, or track measurements of one image or multiple images. Measurement data is recorded in the Measurement Log palette. You can customize the Measurement Log columns, sort data within columns, and export data from the log to a tab-delimited, Unicode text file.
For a video on measurement features, see www.adobe.com/go/vid0029.
Measurement scale
Setting a measurement scale sets a specified number of pixels in the image equal to a number of scale units, such as inches, millimeters, or microns. Once you’ve created a scale, you can measure areas and receive calculations and log results in the selected scale units. You can create multiple measurement scale presets, although only one scale can be used in a document at a time.
Scale markers
You can place scale markers on an image to display the measurement scale. Scale markers can appear with or without a caption displaying measurement scale units.