The Powershot A610/620 has a zoom range of 35mm - 140mm, or 4x. When longer focal lengths are necessary, a teleconverter can be attached via the Lensmate lens adapter. We've tested several teleconverters and the results are presented here. The converters range from 1.54x to 2.2x To calculate the effect of a teleconverter, simple multiply the power of the converter by the focal length of the A610/620s lens. For example, the A610/620 at full tele is 140mm. Multiply 140mm x 1.54x = 216mm focal length (35mm equivalent). The exif information from the camera records the actual focal length as 7.3mm to 29.2.mm. To convert to 35mm equivalent, multiply this number by 4.8.
These samples were taken using the Lensmate 52mm and 58mm adapters and the teleconverters described below. The first image of the pair is the converter with the camera at full telephoto zoom, and the second image shows that point at which vignetting begins to appear (approximate only since the zoom has 7 steps). If the lens was zoomed back further toward the wide setting, the corners would darken and the image would eventually become circular.
