Canon EF 300mm f/4 USM L - Review / Test Report - Analysis
Lens Reviews -
Canon EOS (APS-C)
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As expected for a fix-focal lens the level of distortions is absolutely negligible (0.276%).
Same goes for EF 1.4x II tele-converter combination (-0.177%):
300mm + EF 1.4x II = 420mm:
The chart above has a real-world size of about 120x80cm. Possibly things may get a little worse with extreme close-ups.
Vignetting is basically a non-issue with the lens - at least on a 1.6x DSLR.
Wide-open the vignetting doesn't exceed ~0.3 f-stops which is pretty negligible.
When combined with the Canon EF 1.4x II tele converter the problem is even less pronounced.
MTF (resolution & chromatic aberrations)
The lens delivered a very impressive performance in the lab across the tested aperture
range. In its naked configuration the lens is capable to deliver excellent results without
any significant drop in corner performance. When
combined with the EF 1.4x II tele-converters the performance is (naturally) reduced slightly
but it still reaches very good figures here except at f/11 where we can already see
diffraction effects. So for tripod-based photography the lens is obviously superior to its
Below is a simplified summary of the formal findings. The chart shows in line widths per picture height (LW/PH)
which can be taken as a measure for sharpness. If you want to know more about it you may check out the corresponding
Chromatic Aberrations (CAs)
Similar to most other tele fix-focal lenses chromatic aberrations (color shadows at harsh contrast transitions) are
very low and usually nothing to worry about.
The situation gets a little worse when attaching the Canon EF 1.4x II converter but even here
the issue is still quite acceptable.