This loupe/magnifier with 4X power is specially designed to permit a viewer to simultaneously inspect the whole "picture area" up to 58 mm diameter. The image observed through the loupe is sharp from the center to the edge of the image field because of the critical optical correction for the astigmatism and the curvature of field as well as aberrations relative to the image at the center of the field. Ordinary magnifiers are corrected only for the central image, not for the edges of the field. The manufacturing process for the lenses is very similar to that used for astigmatic photographic lenses. One sees virtually zero distortion around the edges, an indication of the high quality of the optics.
One important feature that makes this loupe different from normal photo lenses is that the position of the effective pupil of the loupe has been placed as far as 25 mm above the upper pole of the loupe, so that an observer can inspect the whole image field by merely moving the eyeballs, without moving the head. This is an extremely beneficial feature for anyone examining many micrographs, in detail, because it makes possible the examination of many micrographs (generally negatives) in the fastest possible time frame and with minimal eye strain. Unit comes with metric scale reticule.