Most framegrabbers have hardware scaling to arbitrary resolutions. The only way to increase the horopter size and maintain range resolution is to increase the disparity search window size, which leads to more computation. Multiresolution methods, which use several sizes of an image, each with its own horopter, are one way to minimize computation. Give the discussion of stereo geometry above, it's easy to see that that range resolution is a function of the range itself. At closer ranges, the resolution is much better than farther ranges.
Range resolution is governed by the following equation.
The range resolution, delta r , is the smallest change in range that is descernible by the stereo geometry, given a change in disparity of delta d . Finally, the pixel size has a direct influence, so that smaller pixel sizes give better resolution. Typically, stereo algorithms can report disparities with subpixel precision, which also increases range resolution. The figure below plots range resolution as a function of range for the STH-V1 stereo head, given a baseline of 8 cm and 6.3 mm lenses. The range resolution is plotted on a log 10 scale to show more detail at closer ranges.