theuerkorn's Full Review: Canon PowerShot SD900 / Digital IXUS 900 Ti Digita...
Canon is celebrating the 10th anniversary of its venerable Elph product line with a bang. What better statement than matching the years with say 10 million pixels? Starting in 1996 with the APS sized film camera that basically defined the class of ultra compact cameras. Now completely digital, the Elph also gets the honors of being one of the first in Canon's line-up to receive the new DIGIC III processor even before any of the currently vastly popular SLRs. Along with it comes an almost unbelievable 10 MPx sensor, which pushes the tiny Elph into serious pixel count areas. (Though Sharp just announced even 12 MPx in an only slightly larger sensor to be available in 2007.)
IN A NUTSHELL
The ten MPx of the SD900 might as well be considered to current limit based on achievable image quality relative to sensor size. Print quality improvements are far less than the 3 MPx difference over and above the SD800 IS suggests, and high resolution video takes its toll in lower frame rates and obviously limited capacity of the max. supported 4GB file size. The video is driven by the latest boom of HD television and not to forget about the incarnation of the two HD disc formats HD-DVD and Blue-Ray. (You're still much better off with a true HD camcorder like Sony's amazing HDR-HC3.)
Yet, the SD900 is a jewel even beyond the sleek titanium housing. It's tiny and fits in virtually any pocket. The face tracking alone makes for a great feature to enable common consumers to shoot sharp portraits. Limitations are typical for a small sensor as found in this class. Best picture quality is realistically only achievable under excellent light conditions (bright daylight) and a steady hand (no IS and tiny photosites kind of magnify camera motion = blur). One of the most impressive features might be the in-camera Stitching Assist which makes it very easy to create panoramic pictures in good quality. A camera like the SD900 is clearly designed to enable consumers to shoot good pictures without having to deal with the technical details.
If quality and control are concerns, an SLR (like the Canon EOS 20D) has a huge advantage of a much larger sensor and ultimately better color rendition as well as much less noise -- not to forget about the artistic freedom due to control over every aspect of taking the perfect picture.
The SD900 is also very similar to the basics of the new 10 MPx Powershot G7, an enthusiast's high-end point-n-shoot camera.
Ignoring the complex algorithms that ink jet printers use to simulate the full spectrum out of 3 - 8 colors, dye sublimation printers are slightly easier to understand (and similar to the professional services). Say you want very good photo quality (300 dpi). That's on the safe side and virtually indistinguishable from the established minimum for photo prints (240 dpi). So your camera should deliver ...
4"x6" -> 2.1 MPx (300 dpi) / 1.4 MPx (240 dpi)
5"x7" -> 3.1 MPx (300 dpi) / 2.0 MPx (240 dpi)
8"x11" -> 7.9 MPx (300 dpi) / 5.0 MPx (240 dpi)
11"x17" -> 16.8 MPx (300 dpi) / 10.7 MPx (240 dpi)
While this math kind of assumes perfect pixels, it's still quite obvious that 8 MPx are the most many of us would "ever" need. Of course that also assumes that you hit the composition just right, the height/width ratio matches and no cropping is needed. More pixels would give you more flexibility, but only in good lighting and with a tripod to minimize blur. Getting sharp pixels becomes increasingly harder the smaller each individual photosite gets -- especially when holding the camera in your hand.
Printing poses another issue that's hardly discussed. It's virtually impossible these days to determine the true (full color) resolution of a printer in ink jets, due to the secrecy most companies shroud their technology with. Further, even for those that have a known fixed resolution --like dye sublimation printers-- the digital picture rarely ever fits exactly and often requires resizing (from the original produced by your camera). That process is especially tricky when having to scale to an odd number like 93%. (When you have 10 pixels and you need to reduce it to 9, you affect information across all 9 pixels since you would try to retain the overall information and cannot simply omit pixels. Hence, even the most sophisticated algorithm introduces additional blur due to the needed interpolation. Say goodbye to your 10 MPx right there.)
Back to the sensor to put things in perspective: The SD800 IS sports 7.1 MPx while the SD900 has 10.0 MPx (Just like the Powershot G7). What sounds like an honest 30% advantage for latter camera is truly 3,648 x 2,736 vs. 3,072 x 2,304 or 16% in each direction. This can be significant, but only when everything is perfect (razor sharp image). Within the above print limitations, the difference is likely to be insignificant for a large number of users.
Body: [****-] - The SD900 is a top model and quite easy to the eyes. The satin finish of the Titanium cladding looks and feels great! The number of chrome coated parts is reduced compared to the SD800 IS which helps reduce fingerprints and makes for a more posh design. Most controls are placed in a convenient location, though the zoom rocker requires some getting used to (especially if you're not familiar with the Elph series). Further, the power button is relatively small (unlike the stylish and functional design of the SD800 IS. Yet, overall size is very similar to the original from 10 years ago -- tiny. There are hints of ergonomic features, but overall you're holding a polished block in your hand without resting areas for the fingers. Tiny buttons and especially a rounded mode selector are not the easiest to use. In other words, you better have your glasses handy and use the included strap to secure the camera to prevent accidental dropping. It's also harder to hold the camera steady. The optical view finder helps in situations where the LCD becomes nearly unreadable (bright light) or to preserve power (by turning the screen off).
Lens: [***--] - The zoom lens ranges from 7.7mm to 23.1mm with a maximum aperture of f/2.8 (wide) - 4.9 (tele). In 35mm film terms the zoom would be a equivalent 37-111mm. Only slightly "longer" than the 105mm equivalent of the SD800 IS, the wide angle is less impressive. This is pretty much the status quo of the compact cameras, but the SD800 IS does better. This is especially surprising since the SD900 lens extends significantly further (a result of the larger sensor). On the bright side, the SD900 has a slightly faster lens which helps out at the tele setting, but is essentially no match for the missing IS. In general I dismiss the digital zoom (4x) on any camera since it doesn't buy anything, the computer software couldn't do. The digital Macro works from 5 to 50cm in the wide setting. Distortion at the wide angle is as expected (~ 1%) and sharpness falls off in the corners, but less than the SD800 IS -- mostly a function of the focal length difference. At the long zoom setting the SD900 is virtually free of distortion. For enthusiasts, the short optical focal length (7.7 - 23mm) is the root cause for a relatively large depth of focus (even at the widest aperture). This helps out in overall sharpness, but also keeps the background for portraits in focus. (Not always desired.) The zoom motor is relatively noisy -- at least compared to Canon's USM drive found in SLR lenses. The integrated lens cover provides only basic protection, but an optional case is highly recommended.
Flash: [***--] - Virtually identical to the SD800 IS the integrated flash is rated to reach up to 4 m, but overall no miracles are to be expected due to close positioning relative to the lens (red eye) and size (power). Hence the SD900 has to rely also on the preflash to reduce the pupil size. There is no hot shoe for an external flash which could solve this problem. The camera software does not provide a tool to post process red eyes (as seen in some other models). The power of the flash does not seem to be regulated and is not distance dependent -- the root cause for overexposed pictures (unless you chose Auto ISO, another way to adjust sensitivity. Generally the flash does a surprisingly good job in macro photography and to support existing light. Difficult light conditions, however, easily upset the little device.
Display: [****-] - The 2.5" screen is identical to the SD800 IS and does a good job in normal daylight, but also has the typical problems in direct sunlight. Viewing angle and resolution (207,000 pixels) are very good. The dreaded color and brightness variation is virtally non-existent within roughly 70 degree ( /-35 mm) and only mild up to rougly 140 degree ( /- 70). All settings are accessed via on-screen display and the menu is easy to navigate, though difficult at first because of the not so obvious structure (categories change via up/down buttons while options can be modified via left/right button). The anti-glare coating is very effective, but also reduces overall brilliance of the colors. (A welcome trade-off.) As usual, an optional case is highly recommended.
Sensor: [****-] - Bigger is better! Marketing apparently focuses on the number of pixels rather than physical size. I already discussed the 10 MPx background, so at this point just the short form. The sensor used on both the the SD900 and the Powershot G7 is slightly bigger (0.556") than the one in the SD800 IS (0.4"). Ultimately that's the reason for similar performance in color gamut and sensitivity, but the SD900 still shows slightly more noise (only noticeable at extremes). This is most likely a result of thermal properties due to higher density. The bayer sensor configuration signs partially responsible for the chromatic aberation that can be observed at extreme contrasts (purple fringes). A general problem for cameras in this design (with exception of the Foveons and Fuji's SuperCCD). Each pixel captures only 1/3 of the color spectrum (either R, G or B), and sophisticated algorithms fill in the missing colors. Artifacts are guaranteed and sharpness on a pixel level reduced.
Processor: [*****] - Canon's new processor is DIG!C III and it also provides the heart beat for the SD900. Supposedly it helps to reduce power consumption and ultimately battery life. The claimed faster operation is easily absorbed by the higher resolution. The face recognition function allows to automatically focus on a person in a picture. With this being the biggest problem in snapshots, there is finally some intelligence to keep the background from taking center stage in perfect sharpness. Other than that, the brain work pretty transparent and is hardly noticeable. Unfortunately, Canon did not add a cache for a burstmode, and the succession is limited by internal processing and the maximum write speed to the memory card.
Quality: [****-] - Considering the the small size of both the camera and the photo sensor, the picture quality in bright light is actually quite good but often not achievable without a tripod. In fact, the results under perfect conditions are quite impressive (in super fine setting to reduce JPG artifacts), but the image quality degrades quickly when using under less ideal conditions (camera shake & low light). The Auto sensitivity ranges from ISO 80 to ISO 400 and the combination of CCD sensor and sophisticated noise reduction algorithms allow for relatively low noise. However, ISO 800 and especially 1600 show significant noise levels. So be sure to know that you need the speed before sacrificing picture quality. Further, the JPG recording finalizes the picture and it's a good idea to review both white balance and exposure histogram before taking it home. Even the best pictures show slight halos around bright features (blurred edges).
Speed: [***--] - The start-up speed consists to a large degree of the lens extension (which also open the lens cover). It takes the SD800 little more than 1 sec. to be ready. Auto Focus is by no means instant but good for the class with roughly 0.2 - 0.4 sec. Once in focus, the SD900 has a minimal delay (0.1 sec of "shutter lag") from pressing the button to actually taking the picture. Not fast enough for action shots, but good for everything else. The exposure time ranges from 15 sec to 1/2000 sec. The SD900 IS is capable of capturing pictures every 0.5 seconds. Ultimately, a camera like this is geared towards that precious snapshot. Unfortunately, the limitation give you two chances per second -- not exactly a candid kind of mode but no slouch either since there is no burst mode and the SD 900 can keep this up until the memory is full (I use a 2 GB RiDATA 150x SD card).
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