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Canon PowerShot S20 Canon packs 3 megapixels and a 2x optical zoom into their "smallest digicam" body! Select a topic Reference: Datasheet PowerShot S20 Sample Images --------------------------------- 1. Intro and Highlights 2. Executive Overview 3. Design 4. Viewfinder 5. Optics 6. Exposure & Flash 7. Shutter Lag & Cycle Time Tests 8. Operation & User Interface 9. Camera Modes & Menus 10. Image Storage & Interface 11. Video, Power, Software 12. Test Results & Conclusion --------------------------------- Print-Friendly Review Version Additional Resources and Other Links Reader Comments on PowerShot S20 Review --------------------------------- Digital Camera Comparometer (TM) --------------------------------- <-- Digital Cameras (Home) <-- Digital Camera Reviews Index <<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:Optics Review First Posted: 4/4/2000

Optics
The S20 features a 6.5 to 13 mm, F/2.9 to F/4.0, 2x zoom lens (equivalent to a 32 to 64mm lens on a 35mm camera), a slight change from the S10's 6.3 to 12.6mm lens. Focus ranges from 26 inches (66cm) to infinity in standard mode and from 4.7 to 26 inches (12 to 66 cm) in macro. As we mentioned earlier, the lens automatically retracts when the camera is switched off, leaving a very smooth front. The actual lens is protected by a mechanical, sliding lens cover that retracts when the camera is turned on and the lens pops out. A bright red autofocus assist light comes on in dim lighting situations which really helps when focusing on dark subjects but can blow your cover in candid shots.
A 4x digital telephoto feature can be turned on and off via the Record menu, giving the S20 zoom capabilities up to 8x. While digital zoom always comes at the expense of image quality, in the form of significantly reduced image resolution, the higher CCD resolution of the S20 means that larger digital zoom images can be produced with less degradation than would be the case in lower-resolution cameras. A quick word of explanation: "Digital Zoom" just crops-out the central portion of the CCD array, and expands the resulting data to fit whatever file size you've selected. Given that the base resolution of the S20 is 2048 x 1536, a 2x digital zoom will still produce an uninterpolated 1024x768 image. Likewise, you can go all the way to 4x digital zoom, and still get a fairly sharp image at 640x480 image size.
The way the digital zoom works on the S20 is the same as on the S10, and sufficiently different from most digicams that it deserves some explanation. On most digicams, digital zoom works fairly independently of the optical zoom: You set the option, and the subject's image suddenly jumps to 2x or 4x its previous size in the LCD viewfinder. The S20 (and earlier S10) work much more the way an uninitiated person would expect them to: With the Digital Zoom option enabled, you control it entirely via the rocker-toggle zoom control, and you have a smooth, continuous range of magnifications available to you. The way this works (going from wide to telephoto, for instance) is that the lens will first cover its 2x optical range. Once the optical zoom reaches its 2x limit, there's a pause, while the lens racks back to its wide-angle position, and the 2x digital zoom cuts in. When this happens, there's no visible change in the viewfinder display, but the camera is now operating in 2x digital zoom mode, with the lens set to wide angle. Continued zooming runs the lens out to its telephoto position, now resulting in a total of 4x magnification (2x optical and 2x digital). If you continue to zoom, the process repeats itself, the lens racking back to the wide-angle position, and the digital zoom jumping to 4x. In this way, you have a continuous zoom range of 8x (2x optical times 4x digital), but as noted earlier, the digital zoom trades off resolution directly for magnification. Still, a very intuitive interface, and the pause as the lens changes settings provides a good cue that you're switching to digital zoom.
The telescoping lens design means the S20 can't accept threaded accessory lenses, but there's fortunately an excellent third-party solution, available from CKC Power. This machined, anodized aluminum bracket screws into the tripod socket, and provides 37mm filter threads directly in front of the lens. (A sample is shown above attached to the camera, holding a 2x telephoto adapter lens.) When screwed on, it's quite secure, and has the added advantage of protecting the extended lens from bumps and knocks. (It of course adds to the cameras bulk, but could easily be carried off-camera in another pocket. A very nicely-made accessory, and one we think should be standard equipment for all S20 owners. (But then we have a freely-admitted fetish for macro lenses and other optical accessories that may not be shared with more "normal" photography enthusiasts...) We don't normally review third-party accessories as part of our camera reviews, but the CKC Power lens adapter for the S20 fills a gap in the basic camera design, by permitting the use of accessory optics. Very highly recommended!
Optically, the lens is of very good quality, showing moderate (0.61%) barrel distortion at its wide angle setting, and slight (0.31%) pincushion distortion at the telephoto end of its range. In another measure of lens quality, the S20's lens shows almost no chromatic aberration (the tendency for a lens to produce colored fringes on objects at the edges of the frame). At wide angle, chromatic aberration is quite low, with just a little color showing around elements in the corners of our resolution target, and almost none at all in telephoto mode. Overall, the S20's lens seems to be of unusually high quality.