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Canon Powershot S70 By: Dave Etchells With the same wide angle lens as its predecessor, the S70 boosts resolution with its 7.1 megapixel sensor, but holds the line on image noise. Select a topic Reference: Datasheet S70 Sample Images S70 Imatest Results S70 Photo Gallery! --------------------------------- 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 --------------------------------- Digital Camera Comparometer (TM) --------------------------------- <-- Digital Cameras (Home) <-- Digital Camera Reviews Index <<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:Optics Review First Posted: 9/30/2004

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The S70 features an advanced built-in, 3.6x, 5.8-20.7mm telescoping zoom lens (equivalent to a 28-100mm lens on a 35mm camera). When the lens cover is opened, the camera powers on and the lens telescopes out from the camera body into its operating position, projecting about 31mm (1.22 inches) from the camera body. It retracts again when the camera is shut off. Focus can be automatically or manually controlled, with a range of 1.4 feet (44 centimeters) to infinity in normal mode. Macro mode features a focus range of 1.6 inches to 1.4 feet (4 to 44 centimeters) in wide-angle mode and 1.0 inches to 1.4 feet (30 to 44 centimeters) in telephoto mode. The greatest magnification in macro mode occurs with the lens at the wide angle end of its range, delivering an impressive minimum area of only 2.28 x 1.71 inches (58 x 43 millimeters). The lens aperture adjusts automatically or manually, with an f/2.8 to f/8.0 range, depending on the zoom setting. (The f/2.8 aperture is only available when the lens is at its wide angle setting. In telephoto mode, the maximum aperture is f/5.3.)

The S70 features some very advanced optics at its core, technology that allows this camera to achieve not only a wider angle of view, but a thinner profile as well. Canon calls it UA, which is shorthand for Ultra-high refractive index Aspherical lens. Canon says they have perfected a way to use highly refractive glass in aspherical lenses. This apparently has been difficult or impossible to do in the past, because highly-refractive glass warps considerably as it cools, introducing errors in the ultra-critical shape of the lens surface. Canon's technical reps say that they estimate that Canon is a year or more ahead of other lens manufacturers in the technology necessary to produce these optics in mass quantities. Because its advanced optics, the S70 has a wider angle of view and a thinner profile than its predecessors, whereas previous lens technology would actually have required a thicker camera to achieve such a wide angle.

In the manual exposure modes (that is, all modes but Auto), the S70 offers a manual focus option. Manual focus is activated by depressing the Manual Focus (MF) button on the left side of the rear panel. A distance indicator appears on the LCD monitor, providing a reference scale for focusing. While the MF button is held down, the up and down arrows of the Omni Selector can be used to adjust the focus (the top of the scale represents infinity). Whatever focus was selected remains in effect when the MF button is released. Autofocus operation can be restored by pressing the MF button a second time. The LCD scale displayed during manual focusing is marked numerically, and a Setup menu option changes the units to meters or feet. This numeric feedback is very handy for times when there's not enough light to see the image on the LCD screen, forcing you to guesstimate the distance. For those times when there is enough light, a small window appears in the center of the viewfinder, showing a 2x-enlarged view of the center of the frame. This helps greatly in determining when you've reached optimum focus, but it would be nice to have an option for even greater magnification, perhaps set via the setup menu.

The S70 offers nine active autofocus (AF) areas in Image Zone modes, arrayed around the center of the frame. In Auto mode, the camera chooses which of the nine to use for focusing, based on which has a subject closest to the camera that it can get a good focus lock on. In Creative Zone modes, the camera pays attention to a single point at the center of the screen by default. With the frame highlighted by pressing the Set button, pressing the right or left arrow buttons on the Multicontroller scrolls it more or less continuously around roughly the central 60 percent of the image area, letting you place it wherever you'd like. Pressing the Set button again locks-in the chosen AF area position and restores the frame to its normal white color. When the camera is focusing, a green highlight around the edge of the frame indicates that the image is focused, while a yellow highlight indicates that the camera is having trouble focusing. If dim subject lighting requires it, a very bright amber LED autofocus assist light on the front of the camera automatically illuminates whenever autofocus is active. (The AF-assist light can be turned off via a menu option.)

The S70's autofocus bracketing option captures three successive images with focus set for the current position, behind, and in front of the subject. The Focus Bracketing function is accessed via the Drive option of the Function menu, and requires that Manual focus be enabled and set. You can adjust the amount of the bracketing via the user interface, but the variation is in arbitrary units. (That is, you can change the relative amount, but there's no indication of just how much the focus is actually being varied. Probably reasonable, given that the variation in focus distance will vary quite a bit as a function of the manually-selected focusing point.)

The S70's 4.1x Digital Zoom must be enabled through the Record menu, as it is disabled by default. Once enabled, it is activated whenever you zoom past the maximum optical telephoto range with the Zoom rocker. Once the Digital Zoom function is activated, press the Zoom rocker to the right and hold it until it stops at maximum telephoto, then release the lever and press it toward the right again. I always warn readers that digital zoom only enlarges the center portion of the CCD image, and compromises the image quality by reducing resolution and enlarging noise patterns. Note that Digital Zoom is not available in the RAW file format.