Ricoh RDC-7A 3 megapixel "Image Capturing Device" for mobile professionals with some unusual capabilities!<<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:OpticsReview First Posted: 8/2/2000 |
OpticsA 3x, 7.3 to 21.9 mm glass lens (equivalent to 35 to 105 mm on a 35mm camera) is built into the RDC-7, with 10 glass elements in seven groups and three aspherical lenses. In normal shooting mode, the focal range extends from 9.4 inches (24 cm) to infinity. A macro mode allows focusing from an amazing 0.4 to 9.4 inches (1 to 24 cm). The camera uses a hybrid autofocus system which works both passively through the lens (TTL) as well as with an auxiliary infrared active autofocus sensor. This combined system seems to give better focus performance than just the passive system (used by most digicams) itself, but still doesn't permit operation in complete darkness. (We speculate that the active autofocus helps achieve "coarse" focus quickly, while the passive, CCD-based system provides the fine focusing.) Aperture is automatically controlled, with a maximum opening of f/2.6 to f/3.4, depending on the zoom setting. The documentation didn't specify the minimum lens opening, but our tests seemed to show that it ranged from f/5.3 to f/7.0, again depending on zoom setting. A manual focus option allows you to control the focus with the up and down arrows on top of the camera.
Distortion on the RDC-7 is moderate to high at the wide angle end, as we measured 0.74 barrel distortion at the widest zoom setting. Alternatively, the telephoto end had practically no distortion at all, we only noticed about a half a pixel of pincushion distortion. Chromatic aberration was also very low, we only noticed about a half to one pixel of coloration on either side of the black target elements in the corners of the resolution target. In total, this is quite a good performance from a digicam lens, relative to others we've tested: Barrel distortion at wide angle is about typical, but pincushion at telephoto and chromatic aberration overall are both better than average.
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