The apochromatic correction of the Digitar lenses reduces color fringing. This has more significance for digital than for conventional photography on film because of the pixel structure and interpolation that both enhance existing color fringes.
The meticulous flattening of the field curvature of this range of lenses does justice to the advantage of the perfectly plane sensor surface.
The recommended distance ranges from infinity up to an image scale of 1:3. Sharpness is still fine even at higher scales but you will probably find the Macro Apo-Digitars to be slightly superior.