the anaglyph to be perceived as graduations of bright to dark. Red and cyan color fringes in the anaglyph display represent the red and cyan color channels of the parallax-displaced left and right images. The viewing filters each cancel out opposing colored areas, including graduations of less pure opposing colored areas, to each reveal an image from within its color channel. Thus the filters enable each eye to see only its intended view from color channels within the single anaglyphic image. Red-green glasses are also usable, but may give the viewer a more strongly colored view, since red and green are not complementary colors. Red sharpened anaglyph glasses Simple paper uncorrected gel glasses, cannot compensate for the 250 nanometer difference in the wavelengths of the red-cyan filters. With simple glasses, the red filtered image is somewhat blurry, when viewing a close computer screen or printed image. The red retinal focus differs from the image through the cyan filter, which dominates the eyes' focusing. Better-quality molded acrylic glasses frequently employ a compensating differential diopter power (a spherical correction) to balance the red filter focus shift relative to the cyan, which reduces the innate softness and diffraction of red filtered light. Low-power reading glasses worn along with the paper glasses also sharpen the image noticeably. The correction is only about 1/2 + diopter on the red lens. However, some people with corrective glasses are bothered by difference in lens diopters, as one image is a slightly larger magnification than the other. Though endorsed by many 3D websites, the diopter "fix" effect is still somewhat controversial. Some, especially the nearsighted, find it uncomfortable. There is about a 400% improvement in acuity with a molded diopter filter, and a noticeable improvement of contrast and blackness. The American Amblyopia Foundation uses this feature in their plastic glasses for school screening of children's vision, judging the greater clarity as a significant plus factor. Anachrome filters Plastic glasses, developed in recent years, provide both the diopter "fix" noted above, and a change in the cyan filter. The formula provides intentional "leakage" of a minimal (2%) percentage of red light with the conventional range of the filter. This assigns two-eyed "redness cues" to objects and details, such as lip color and red clothing, that are fused in the brain. Care must be taken, however, to closely overlay the red areas into near-perfect registration, or "ghosting" can occur. Anachrome