Canon EF 17-40mm f/4L USM wide-angle uniformity using Canon EOS 5D
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To measure lens vignetting and light fall-off we photographed a white
target with a highly diffused custom filter. The lenses were tested at their
widest focal lengths with the aperture wide open using a Canon EOS-5D in
Aperture Priority mode. The images were analysed with Imatest and the full
areas presented here at a reduced resolution. Bigger percentages are better.
All three lenses performed similarly here, with light falling off by almost
two thirds by the time it reached the corners. Light fall-off is always
a problem with wide-angle lenses, but particularly so for those which have
to perform for a full-frame sensor or 35mm film.
Full frame sensors further accentuate the problem because with wide angle lenses, the light rays are striking the sensor's micro-lenses towards the corners at a shallower angle, effectively rendering them less sensitive. |
Canon EF 17-40mm f/4.0L USM |
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Canon EF 24-105mm f/4L IS USM |
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Canon EF 24-70mm f/2.8L USM |
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17-40mm at 17mm f4
Mean corner fall-off: 34.3% |
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24-105mm at 24mm f4
Mean corner fall-off: 33.3% |
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24-70mm at 24mm f2.8
Mean corner fall-off: 34.1% |
Canon EF 17-40mm f/4L USM telephoto uniformity using Canon EOS 5D
To measure lens vignetting and light fall-off we photographed a white
target with a highly diffused custom filter. The lenses were tested at their
longest focal lengths with the aperture wide open using a Canon EOS-5D in
Aperture Priority mode. The images were analysed with Imatest and the full
areas presented here at a reduced resolution. Bigger percentages are better.
Once again, the full-frame coverage presents a challenge to any lens, with
all three scoring lower than many equivalent focal length lenses would on
cropped bodies. That said, the 17-40mm delivers the best result here with relatively little fall-off compared to the others. |
Canon EF 17-40mm f/4.0L USM |
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Canon EF 24-105mm f/4L IS USM |
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Canon EF 24-70mm f/2.8L USM |
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17-40mm at 40mm f4
Mean corner fall-off: 63.1% |
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24-105mm at 105mm f4
Mean corner fall-off: 54.5% |
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24-70mm at 70mm f2.8
Mean corner fall-off: 52% |
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