MTF Charts

MTF (Modulation Transfer Function) measures how well a lens reproduces contrast at different levels of detail. An MTF chart plots contrast (vertical axis, 0-1) against distance from the image center to the edge (horizontal axis). Higher values mean sharper images.

MTF charts typically show two line types: sagittal (parallel to a line from center to corner) and meridional (perpendicular to that line). When both lines are close together, the lens has low astigmatism. When they diverge, point light sources become elongated in one direction.

Charts are usually measured at two spatial frequencies: 10 lp/mm (line pairs per millimeter) for contrast, and 30 lp/mm (or 40 lp/mm on higher resolution tests) for fine detail resolution. The 10 lp/mm lines tell you about overall contrast and “pop”; the 30 lp/mm lines tell you about resolving power and fine texture.

A great lens shows both lines above 0.8 across the frame at 10 lp/mm, and above 0.6 at 30 lp/mm. A lens that starts high in the center but drops sharply toward the edges has good center sharpness but weak corners — common in fast primes wide open.

MTF charts have limitations: they are measured at a single aperture (usually wide open and f/8), do not capture chromatic aberration, coma, or flare, and lab conditions do not match real-world shooting. Use them as one input alongside field reports, sample images, and optical scores.

In Wuseria, the center/corner stopped and wide-open scores are derived from MTF data and lab tests. They are simplified to a 0-2 scale for quick comparison across the entire lens lineup.