(See Chart Features for general chart features - changing scales, copying to clipboard etc)
The Image Motion chart shows how the image of the FoCal target moves across the image sensor as the test is run.
- Green circles - image motion (in pixels) for individual shot
- Green area - the range of motion for all shots at each AF Microadjustment point
The Image Motion chart shows the absolute number of pixels moved for each image compared to the first image captured. This metric does not include a direction - simply the overall number of pixels the image has moved.
Typically, the Image Motion should be significantly less than 10 pixels, and a repeatable higher value could indicate misaligned lens optics, camera movement or vibration during the test or other environmental or lens issues.
The example above shows a good quality result, with movement of less than a single pixel.
The following example is from a low cost and quite old design lens (the Canon EF 28-90mm). You can clearly see the movement of the image across the test which is likely due to slightly misaligned optics and the fact that the front element rotates during focusing (common on cheaper lens designs):