Image Quality of Canon EF 100-400mm f/4.5-5.6L

This post shows a quick comparison of the image quality of our Canon EF 100-400mm f/4.5-5.6L zoom lens in comparison with our Canon EF 400mm f/5.6L prime lens which is somewhat of a gold standard for resolution and images free of chromatic aberration.

To perform the test, I mounted a scanner-bed test target on the wall and mounted the lenses on a tripod. Images were taken with a Canon 60Da using center-point AF and mirror lockup to ensure best focus. I performed a series of tests at f/5.6, f/8, and f/11.  Both lenses worked well fully open and didn't improve significantly in either resolution or CA as the lens is stopped down.

Here is a pixel-peeping comparison of the image at the center of the frames:

Canon EF 400mm f/5.6L - Center frame at 400mm, f/5.6

Canon EF 100-400mm f/4.5-5.6L - Center frame at 400mm, f/5.6

... and in the upper right corner of the frame:

Canon EF 400mm f/5.6L - Upper right corner at 400mm, f/5.6

Canon EF 100-400mm f/4.5-5.6L - Upper right corner at 400mm, f/5.6

As expected, the prime lens wins in contrast, resolution, and color-free image. However, I am pleasantly surprised by how well the zoom lens is doing. At 100mm and 200mm, the test results look better than the 70-200mm f/4L lens which I have been using for astro-photography. It looks like the 100-400mm will also be worth star testing.