Canon Lens EF 400mm 1:4.0 DO IS USM

Aperture Range [f] 4.0 to 32 Closest Focus 3.5m / 11.5 ft.
Dimensions 233mm x 128mm / 9.2 in. x 5 in. Magnification Ratio 0.12x / 1:8.3
Weight 1.94kg / 4.3 lb Filter Size 52mm drop in or 6" to cover the hood

Analysis of this lens resolution chart revealed that it is the sharpest at f/5.6. The image quality on a camera's chip depends on the distance from the center, as shown below, with the average resolution in hundreds of line widths per picture height (LW/PH) given below each chart.

lens quality test

The sharpness is relatively uniform throughout the entire frame, and even reaches the theoretical maximum (resolution of "37" is the max. theoretical number in this test) at f/5.6 in the center. Contrast suffers slightly at wide open aperture (note also that the red center dot as well as the thick black circle are not even in color).

The lens vignetting is negligible. Chromatic aberration is minimal. The size of the circles remain constant trhoughout the frame, with well below 1% difference. The circles have also perfect proportion (no ellipses). The lens has virtually no distortions.

This is a high quality lens, better than 400mm f/5.6 lens, because it's brighter and has the image stabilization, and not because of its sharpness (that is comparable). Evenness of the colors at wide apertures (off center only) may be a reason of concern.

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