Canon EOS 400D / Digital Rebel XTi lens upgrade wide-angle uniformity
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To measure and compare light fall-off at wide angle, we photographed a white target using a
highly diffused custom filter with each lens at its
shortest focal length and the aperture wide open.
The images were then analysed with Imatest and the full
areas presented here at a reduced resolution. Bigger percentages are better.
As with the previous Geometric distortion results, the EF 17-40mm performs best here since it's corrected for a larger and more demanding full-frame body. Interestingly the second best result actually comes from the budget EF-S 18-55mm, followed by the EF-S 17-85mm and finally the EF-S 17-55mm, which loses just over half of its brightness in the extreme corners. To be fair, the EF-S 17-55mm offers an f2.8 aperture throughout its range, but if light fall-off and dark corners really bother you, the EF-S 17-55 and EF-S 17-85 are best avoided at wide angle.
Note: to see how the EF 17-40mm performs on a full-frame body in this respect, check the uniformity results of our Canon 24-105mm review. |
Canon EF-S 17-55mm f/2.8 IS USM |
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Canon EF-S 17-85mm f/4-5.6 IS USM |
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Canon EF-S 18-55mm f/3.5-5.6 |
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Canon EF 17-40mm f/4.0L USM |
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17-55mm EF-S at 17mm f2.8
Mean corner fall-off: 46.8 |
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17-85mm EF-S at 17mm f4
Mean corner fall-off: 57.8% |
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18-55mm EF-S at 18mm f3.5
Mean corner fall-off: 68.8% |
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17-40mm EF L at 17mm f4
Mean corner fall-off: 79.4% |
Canon EOS 400D / Digital Rebel XTi lens upgrade telephoto uniformity
To measure and compare light fall-off at telephoto, we photographed a white target using a
highly diffused custom filter with each lens at its longest focal length and the aperture wide open.
The images were then analysed with Imatest and the full
areas presented here at a reduced resolution. Bigger percentages are better.
Our last optical result actually sees the budget EF-S 18-55mm perform best of all, although the EF 17-40mm is right behind it; this is still a great result for the EF-S 18-55mm though, as the EF 17-40mm is an 'L' model that's also designed for a full-frame body. Following the wide angle results above, the EF-S 17-85mm comes third and the EF-S 17-55mm last in this test. Again you have to take the latter's f2.8 aperture into account, but either way, images taken with both of these lenses can noticeably darken in the corners.
Note: to see how the EF 17-40mm performs on a full-frame body in this respect, check the uniformity results of our Canon 24-105mm review. |
Canon EF-S 17-55mm f/2.8 IS USM |
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Canon EF-S 17-85mm f/4-5.6 IS USM |
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Canon EF-S 18-55mm f/3.5-5.6 |
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Canon EF 17-40mm f/4.0L USM |
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17-55mm EF-S at 55mm f2.8
Mean corner fall-off: 60.8% |
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17-85mm EF-S at 85mm f5.6
Mean corner fall-off: 77.5% |
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18-55mm EF-S at 55mm f5.6
Mean corner fall-off: 83.8% |
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17-40mm EF L at 40mm f4
Mean corner fall-off: 82.2% |
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