The lenses on the A610 and A620 are identical. We refer to the A620 here only because that's the camera used in this test. Unless you only intend to use the images for the web, we recommend downloading and printing the original large/superfine jpeg file and printing at your intended size to make a good evaluation of a lens you might be interested in. The appearance of an image on your monitor will not be the same as when printed.
Vignetting: It seems counterintuitive that some of the wide converters that didn't vignette on the G6 should do so on A620 which has a much smaller lens diameter. But the way the elements move in relation to each other, and difference in length of the lens going from wide to tele are very different too. There is only 1mm difference between the position of the zoom on the G6 between tele and wide. On the A620, the lens retracts 12mm going from tele to wide. This greater distance between the end of the zoom lens and the conversion lens increases the potential for vignetting with wide angle converters.
Asymmetrical vignetting: We used an A610 and 2 A620s for this test and the A610 and one of the A620s showed more vignetting on one side (both corners on one side). This is probably caused by a slightly off-center sensor, so when the image circle projected by the lens doesn't quite cover the rectangular mask over the sensor, the vignetting is asymmetrical. This won't be apparent unless certain converters are used, (it can also be seen as a teleconverter is zoomed back) and even the Canon recommended wide converter for the A620 (the WC-DC58N) darkened the right side corners on one of our A620s.
Barrel Distortion: The barrel distortion of the A620 is corrected almost perfectly by programs such as Imaging Factorys' Debarrelizer - see the corrected DCR730 image here (The A620s barrel distortion at the wide end is fairly uniform, but flattens out slightly near the corner). Barrel distortion can be counteracted by the optics of converters like the Raynox DCR6600 which produces a near-rectilinear image on the A620, or increased by converters like the Raynox DCR730. In all fairness, shooting tall buildings is a worst possible scenario for a wide angle lens, and many users will be shooting in a more natural setting in which barrel distortion is less noticeable.
Zooming: Some users like to use the whole zoom range of their camera with a wide converter mounted. For this reason, we show how well the wide converter handles the telephoto end of the zoom as well as the wide. All of the converters did very well in this respect. To calculate focal length with a converter added to the camera, multiply the focal length of the camera by the focal length of the converter. Example: It's known that the focal length of the A620s built in lens at full wide is 7.3mm (or 35mm in film equivalent). With the WC-DC58N .7x attached, the focal length is 7.3 X .7 = 5.11mm, or in film equivalent, 35 X .7 = 24.5mm. The multiplier therefore is 4.8.
