# Absolute Difference Mode

Absolute Difference mode determines the sharpness of an image by computing the difference between each pixel and a corresponding pixel at a user-specified offset. Sharper images tend to have a greater difference in pixel values:

By examining your images and specifying meaningful X Distance and Y Distance offset values, you can have the tool examine the image efficiently in determining the difference of the offset pixel pairs.

The tool returns a sharpness score by calculating the average difference between pixel pairs at all locations within the image and scales the value to the range 0.0 to 1.0.

Some notes about Absolute Difference mode:

- Performs faster with larger offsets, but performs slower than Auto-Correlation mode for smaller offsets
- Requires that you know the size of features of interest in the image in order to return reliable results.
- Cannot determine the sharpness of an image containing diagonal features
- Might not return reliable results on high-freqency images, where pixel values change rapidly on a short distance scale