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Canon PowerShot A640 wide-angle uniformity comparison
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To measure and compare the Canon PowerShot A640's
lens vignetting and light fall-off we photographed a white target with a
highly diffused custom filter using it and a number of rival models.
Here are the results for each camera with their built-in lenses set to their
widest focal lengths with the apertures wide open and the focus set to infinity.
The images were analysed with Imatest and the full areas presented here
at a reduced resolution. Bigger percentages are better.
The image left was taken with the Canon PowerShot A640 zoomed-out to 7.3mm with its aperture wide open. |
7.3-29.2mm at 7.3mm f2.8
Mean corner fall-off: 67% |
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| Here the light falls off in the corners to an average of 67% of the center
measurement, which is below the results of the other cameras tested here. That said, it's not so bad you'd notice it in most day-to-day shots, but the Fujifilm F30 and Sony N2 are both comfortably superior in this respect. |
Fujifilm FinePix F30 |
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Panasonic Lumix DMC TZ1 |
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Sony Cybershot DSC N2 |
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8-24mm at 8mm f2.8
Mean corner fall-off: 80.8% |
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5.2-52mm at 5.2mm f2.8
Mean corner fall-off: 72.8% |
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7.9-23.7mm at 7.9mm f2.8
Mean corner fall-off: 79.6% |
Canon PowerShot A640 telephoto uniformity comparison
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To measure and compare the Canon PowerShot A640's
lens vignetting and light fall-off we photographed a white target with a
highly diffused custom filter using it and a number of rival models.
Here are the results for each camera with their built-in lenses set to their
longest focal lengths with the apertures wide open and the focus set to
infinity.
The images were analysed with Imatest and the full areas presented here
at a reduced resolution. Bigger percentages are better.
The image left was taken with the Canon PowerShot A640 zoomed-in to 29.2mm with its aperture wide open. |
7.3-29.2mm at 29.2mm f4.1
Mean corner fall-off: 77.7% |
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Here the light falls off in the corners to an average of 77.7% of the center measurement, which while again the worst result of the group, would still be hardly noticeable in general-use. Once again the Fujifilm F30 and Sony N2 deliver the best results in this test. |
Fujifilm FinePix F30 |
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Panasonic Lumix DMC TZ1 |
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Sony Cybershot DSC N2 |
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8-24mm at 24mm f5
Mean corner fall-off: 88.1% |
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5.2-52mm at 52mm f4.2
Mean corner fall-off: 81.8% |
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7.9-23.7mm at 23.7mm f5.4
Mean corner fall-off: 86.9% |
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