Olympus C-50 ZoomOlympus packs a 5.0-megapixel CCD into an ultra-compact body, with a host of advanced features too.<<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:OpticsReview First Posted: 11/26/2002 |
Optics
The
Olympus C-50 is equipped with an all-glass lens, with seven elements in six groups.
The 3x, 7.8-23.4mm lens provides a focal length range equivalent to a 38-114mm
zoom on a 35mm film SLR. (That's a moderate wide angle to a normal telephoto.)
Apertures range from f/2.8 to f/8, with the maximum aperture setting ranging from
f/2.8 to f/4.8 as the lens is zoomed from wide angle to telephoto. Normal focusing
distance extends from 1.6 feet (0.5 meters) to infinity. A Macro setting focuses
from 0.7 to 1.6 feet (0.2 to 0.5 meters). The Macro / Spot button on the back
panel adjusts the focus range for closeup subjects, and includes an option for
spot metering in either Macro or normal focusing mode.
Autofocus is determined through the lens, using a contrast detection method. A green circle lights solid in the viewfinder display whenever focus is set, and flashes if the camera is having trouble adjusting focus (as does the green LED lamp next to the optical viewfinder). The C-50 doesn't offer a manual focus option, and there's no autofocus-assist light, but it still managed to focus pretty well in dim lighting. During my low-light test, the C-50 often indicated that it could not accurately determine focus, but the resulting images turned out to be well-focused. As to what the camera thought its low light limit was, the focus indicator on the LCD display indicated that the camera could focus down to a light level somewhere between 1/2 and 1 foot-candle. The C-50 should thus be able to handle night scenes under typical city streetlighting, a light level of roughly 1 foot-candle. Still, I'd really like to see an AF illuminator on the camera, as it could greatly extend the C-50's usefulness under dark indoor shooting conditions.
While the C-50's lens provides up to 3x optical zoom, the camera's 4x Digital Zoom increases that magnification to a maximum of 12x (albeit with the usual digital-zoom-induced quality degradations in the resulting images). Digital zoom is activated through the Record menu and controlled by the Zoom Lever on top of the camera. Since digital zoom just crops out and enlarges the central pixels from the CCD's image, it directly trades resolution for magnification. This will result in very soft images if you're working at the camera's maximum five-megapixel file size, but can be useful if you're only shooting at 640 x 480 anyway. (For web or email use.)
Optical distortion on the C-50 was quite high at the wide-angle end, where
I measured approximately 1.05 percent barrel distortion. The telephoto end fared
much better, as I measured only three pixels of barrel distortion (about 0.1
percent). Chromatic aberration is also moderately high, showing about five or
six pixels of coloration on either side of the target lines. (This distortion
is visible as a very slight colored fringe around the objects at the edges of
the field of view on the resolution target.) At telephoto focal lengths, I also
saw quite a bit of flare in the corners of the frame. (Visible on my resolution
target shots, where the boundaries of some of the dark target elements become
fuzzy in the corners of the frame.)
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