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Modulation Transfer Function (MTF)

The Sigma-supplied MTF chart indicates a lens with very good contrast wide open, indicating well-controlled aberrations. It’s not clear if MTF is computed or measured. Zeiss measures MTF and doesn’t ship a lens unless it meets specifications—computed MTF means that’s the best possible result, and real lenses might not perform as well.

The red lines are at 10 line pairs/mm and the green lines are at 30 line pairs/mm. The Sigma description states that the MTF chart is wide open (f/1.4), which is an outstanding MTF curve for an f/1.4 lens, and field shots do tend to confirm it. Compared to the Zeiss ZF 50/1.4 Planar MTF chart, the Sigma maintains notably higher contrast over much of the field at 10 lp/mm, a remarkable performance. Beyond that it’s hard to be sure; Sigma’s results may be computed (not measured) and are at 10/30 lp/mm vs 10/20/40 lp/mm for the Zeiss. Interpolating, fine detail MTF is probably a bit better with the Sigma at f/1.4.

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Diglloyd DAP is DSLR-oriented, but also contains workflow and other topics. Much of the focus is on Canon and Nikon but also Pentax and Pentax medium format.

Special emphasis is placed on lens evaluation, focusing on Canon and Nikon and Sigma lenses, but with a few others like Rokinon/Samyang.

  • Make better images by learning how to get the best results right away.
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  • Optical quality analysis of field curvature, focus shift, sharpness, flare, distortion, and performance in the field.

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Sigma 50/1.4 MTF, 10/30 lp/mm @ f/1.4

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