# Auto-Correlation Mode

Auto-Correlation mode determines the sharpness of an image by calculating the normalized correlation coefficient between an image and a slightly offset portion of the same image. A higher value between the two locations indicates a greater chance the sharpness of the image can be improved.

The tool calculates the normalized correlation at four offsets within the image. The tool takes the smallest value of the four offsets as a measure of blur in the image:

The tool returns a sharpness score in the range of 0.0 to 1.0, where higher scores indicate a higher degree of image sharpness.

Some notes about Auto-Correlation mode:

- Works well for most images
- Good for low-contrast images
- Larger images typically more processing time to generate a sharpness score than other Image Sharpness modes