Are you an architectural or landscape photographer? This was the ultimate extreme wide-angle lens with the least distortion. The latter was achieved with a partially symmetrical construction on a breathtakingly short flange focal length. Schneider had pushed everything to the limit so that this lens could be used safely on the ALPA. The ALPA Helvetar 5.6/28 mm version is equipped with an exclusive HPF-like distance scale in meter and mirrored 180 degrees one in feet. Due to the square mount, the lens was usable in either position.
The image circle of 90 mm allowed generous movements with digital backs. But the extreme sensitivity to oblique ray paths challenged almost all digital backs with pixel sizes below 9 or 6.8 microns. The result was a very strong colour cast that was often difficult to correct. A special centre filter brought some relief.
Even today, this lens is still the ultimate in high resolution achromatic digital backs and black and white photography in terms of high imaging performance and low weight/compact dimensions.