# Image Requirements

In addition to the requirements for the design of the calibration plate, there are also specific requirements for the acquired image of the plate:

- The dots must be between 10 and 40 pixels in diameter.
- The grid must contain no less than 16 and no more than 2000 dots.
- There must be at least 8 pixels between dot centers.
- The center-to-center distance between any two adjacent dots in any row or column may not exceed 512 pixels for plates with fiducial marks or 1024 pixels for plates without fiducial marks.
- No dot may be closer than one-half the diameter of a dot to the edge of the image (there must be a quiet zone containing no dots around the image edge, and this quiet zone must be at least half as wide as a dot).
- The optical axis of the camera used to acquire the image must be within 30 degrees of perpendicular to the plate. Note that this requirement does not exist for checkerboard plates.

If the acquired image does not meet these requirements, the tool may not operate correctly.

In general, the greater the number of visible dots within the image, provided that the image and plate meet the listed requirements, the more accurate the calibration will be.