Dense cloud at lower resolutions

[timwhittome]

How does PS calculate the dense cloud at lower resolutions than Ultra High? For example, at High does the program look at every second pixel (or fourth pixel for Medium etc) or does it reduce the resolution of the photographs by successive factors of 2 and use averaged values for every pixel in the reduced images?And would this make a difference to the accuracy of resulting DEMs?

[madekwe]

Images are downscaled corresponding to the target quality selected:

    Ultra High - no scaling
    High - images are downscaled two times by each side
    Medium - downscaling four times by each side
    Low - eight times
    Lowest - sixteen times