Olympus Camedia C-770 Zoom4.0 megapixels, a sharp 10x zoom lens, a unique flash head, and loads more features!<<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:OpticsReview First Posted: 07/06/2004 |
Optics
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The
Olympus C-770 is equipped with an all-glass lens, with 11 elements in seven
groups. The 10x, 6.3-63mm lens provides a focal length range equivalent to a
38-380mm zoom on a 35mm film SLR. (That's a moderate wide angle to quite a long
telephoto.) Apertures range from f/2.8 to f/8, with the maximum aperture setting
dependent on the lens zoom position, ranging up to f/3.7 at the maximum telephoto
position. The C-770's normal minimum focusing distance supposedly extends from
3.9 to 6.6 feet (1.2 - 2.0m) as the lens ranges from wide angle to telephoto,
but in practice, I found that there was no difference in behavior between "normal"
focusing and "normal macro" mode: The camera always seemed to focus
as close as about three inches at wide angle, and around four feet at telephoto
focal lengths. - The close end of this range matches Olympus' spec for closest
focus in normal macro mode at wide angle, but the minimum distance in telephoto
mode is quite a bit further than the 2.0 feet that Olympus claims. Through the
Record menu, a Super Macro option lets the camera focus as close as 1.2 inches
(three centimeters), but the lens focal length in this mode is fixed at an intermediate
focal length near the wide angle end of the lens' range.
Autofocus is determined through the lens, using a contrast detection method. This means that the autofocus will work properly with auxiliary lenses, although it should be noted that add-on lenses will usually affect a camera's focusing limits: Don't expect the C-770 to focus as close as it usually does when it has a telephoto adapter attached. A green dot lights solid in the viewfinder display whenever focus is set, and flashes if the camera is having trouble adjusting focus. An optional Full-time AF mode continuously checks focus and refocuses as conditions change. This assures that the camera is more likely to be focused on a moving subject when you're ready to shoot; but it also uses more battery, so use this feature wisely. Also, note that, with stationary subjects, the continuous AF option does nothing to reduce shutter delay. Two AF area modes are available as well, iESP and Spot. In iESP mode, the camera bases focus on the entire frame, automatically determining the primary subject, based on proximity to the camera. Spot mode looks at only the very center of the frame, the area within the black AF target marks on the viewfinder display. The C-770 also lets you adjust the AF area, through an option in the Record menu. Once enabled, you use the arrow keys to move the AF target marks anywhere in the frame (though only while in Spot AF mode). Finally, the C-770 features a manual focus option. Pressing and holding the "OK" button displays the AF/MF focus menu, as well as a distance scale that you can set to meters or feet. You then adjust focus with the up and down arrow keys. As an aid to accurate focusing, the center portion of the view enlarges whenever you're actively adjusting the focus setting..
The C-770's lens barrel incorporates body-mounted filter accessory threads that couple to Olympus' range of accessory lens kits, which extend the camera's telephoto, wide-angle, and macro shooting capabilities. (Note that an Olympus adapter tube, part number CLA-4, is required to permit mounting the auxiliary lenses beyond the furthest extension of the C-770's telescoping lens assembly.)
While the C-770's lens provides up to 10x optical zoom, the camera's 4x Digital Zoom increases that magnification to a maximum of 40x, although the digital zoom brings with it the usual reduction in resolution. Digital zoom is enabled through the Record menu and controlled by the Zoom Lever on top of the camera. Since so-called "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 four-megapixel file size, but can be useful if you're only looking for 640 x 480 pixels for web or email use.
As an alternative to the blurring effect of the interpolation used with normal digital zoom, the C-770 offers a "Super Zoom" mode. This seems to be an unusual combination of digital telephoto and optical zoom. In Super Zoom mode, image resolution is forced to 1600x1200, and the zoom range is extended by about another 40%. This sounds a lot like a digital zoom function, where the image is being cropped to 1600x1200 to give the greater telephoto effect. What's different about the Super Zoom mode though, is that there's obviously some motion of the lens elements as you zoom from the normal maximum telephoto position to the "super tele" setting. My guess is that the C-770 uses a combination of cropping and optical zooming in its Super Zoom mode, to achieve a smooth 14x zoom range from wide-angle (where it uses the full sensor area, resampling the full frame to 1600x1200) to maximum telephoto (where it uses only the central 1600x1200 chunk of sensor pixels, but does no resampling). An interesting concept, basically giving you an option to use the camera as either a four-megapixel, 10x zoom model, or two-megapixel, 14x zoom model.
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