Using Imatest, industry-standard software designed to give quantifiable data demonstrating optical and photographic performance, we compared the sharpness, distortion, falloff, flare, and chromatic aberration of the lenses. We also ran a series of real-world autofocus tests, covering low contrast, low light, and speed performance.

MTF is a test procedure that gives us an evaluation of how the lens renders both resolution and contrast, two features that are inexorably linked in how a lens appears to render fine detail. Not only must a lens transmit the borders of a shape accurately, but it must transmit the tonal values, or contrast, of that shape as well.

SQF, on the other hand, gives us an evaluation of how a lens’ performance will be perceived within the limits of the human eye. Imatest actually cross-references the MTF values of the lens with the known MTF values of the human eye and give us an indication of a very practical criteria: how we see the results of the lens performance. This brings us back to one of our cornerstones of testing: if you can’t see the difference, how important is it when all else is said and done?

In addition to the optical data provided, we’ve included a few samples illustrating the effects of depth-of-field and the “bokeh” effect compared between the two lenses. This may, in fact, be one of the single most important comparisons to a photographer using these lenses for portrait or wedding applications. To the untrained eye, sharpness is often subtly distinguishable, the softness and texture of a good shot’s background is undeniable.

We ran the tests at three baseline apertures. First, we compared the lenses at the maximum apertures, f1.2 and f1.8. Our second comparison is at the same aperture, f1.8, to establish a real-world comparison based on the same exposure. Finally, we looked at the two lenses at f7.1, approximately two-thirds stopped down to minimum aperture, in an attempt to get an indication of how the lenses will compare when they approach maximum sharpness.