Canon EF 300mm f/4 USM L IS - Review / Test Report - Analysis
Lens Reviews -
Canon EOS (APS-C)
Page 2 of 3
As expected for a fix-focal lens the level of distortions is negligible (0.205%):
The chart above has a real-world size of about 120x80cm. Possibly things may get a little worse with extreme close-ups.
Vignetting is almost a non-issue with the lens - at least on a 1.6x DSLR.
Wide-open vignetting doesn't exceed ~0.3 f-stops in the naked lens which is already on the verge of
being negligible. One stop down vignetting is basically non-existent. When combined with the Canon EF 1.4x II
tele converter the problem is even less pronounced.
Update 02/22/2006: Markus Stamm was so kind to provide a second sample of the EF 300mm f/4 USM L IS
for testing. Interestingly the new sample performed significantly better with
excellent quality straight from wide-open aperture.
The performance peak is reached one stop down with only an insignificant decrease
towards f/8. Combined with the EF 1.4x II there's a slight but visible drop in resolution
but the center remains in very-good territory followed by still good+ borders.
Subjectively (not measured) the combination also seems to suffer from a loss of contrast.
The characteristic of the 2nd sample seems more in line to what you can expect from
a lens in this price class. However, this second sample was serviced TWICE before reaching
its current condition.
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)
The CAs (color shadows at harsh contrast transitions) are well below disturbing limits both regarding the
naked lens as well as for the teleconverter combination.
The lens is capable to produce a very fine bokeh but flare in contra light is a weak point which can't be surprising
regarding the large number of elements in this lens.