Canon PowerShot SX40 HS: Video and Image Quality

Video Quality
The SX40 has full 1080p HD video and allows some specialty capture modes including simulating miniatures and creating super slow motion movies. The camera can also record in 720p and VGA resolutions if you need to save space or only need a lower quality version of the output. You can capture stills while you are shooting video simply by pressing the shutter button.

The 1080p HD video quality from the SX40 is in general excellent. Images are crisp and colorful. However, in my test situations, issues arose with auto-focus and low-light action recording. Video I shot of Occupy Wall Street protestors shows that the focus drifts in and out and doesn't stay locked onto the players the way it would with a quality camcorder. The actual image quality however is very similar to watching the same scene on one of the HD news channels that was covering the event with much more expensive equipment.

And in the low-light video of the train layout the panning becomes a little jerky and hard to follow. The moving train also becomes slightly blurred. For a point and shoot with a relatively slow lens these failings are hardly unique.



Image Quality
Understanding the SX40 starts with understanding just how large its zoom range really is. Below is a photograph of a model train layout at 24mm, the camera's widest field of view, and 840mm, its narrowest. The difference is almost mind-blowing. The tiny little yellow house in the first image is the same one that is full frame in the second image, just by using the lens zoom - a real zoom, without any digital effects.


Wide Angle

Telephoto

Just as impressive is that these images were taken hand-held in low light, at 1/30th and 1/20th of a second, respectively. Since the conventional wisdom is that a shutter speed of 1 over the f-stop is needed for a sharp image, the zoomed version should have needed a shutter speed like 1/750 or better to be tack sharp. 1/20th of a second is 5-stops slower, showing that the Vibration Reduction on the SX40 is capable of something close to 5 stops of assistance, an amazing number, especially for a sub-$500 camera.

While the lens on the SX40 may not be the fastest or even sharpest among high-end point and shoots, the combination of the lens and the on-board DIGIC5 processor create excellent images. Any light falloff that the lens may have appears to be nicely corrected by the time we see the JPEG out of the camera.

Similarly Canon's image processing does an excellent job of computing exposure and creating a clean, crisp image even at the default settings. My only complaint about exposure is that the SX40 has a slight tendency to expose for the shadows in high contrast scenes. This provides for excellent rendering of the subject in backlit conditions, but at the expense of blowing out the background highlights. In most cases that result will provide the best overall image, since we're usually interested more in the subject than the background, but for landscapes or other shots where the background is important, it may be necessary to dial in some minus exposure compensation.

One big problem for purists is the lack of a Raw shooting mode. All captured images are passed through the camera's own image processing and JPEG compression firmware. As good as that is with the new DIGIC 5 chip it limits the variety of post-processing options available. Now that other similarly priced point and shoot cameras - the Powershot G12, Powershot S100, and Panasonic Lumix LX5 for example - it is surprising that it isn't available in the SX40.

Without the option to capture Raw images, it is necessary to set the white balance prior to shooting. Since this is a somewhat tedious process, most of the time it gets left to the camera's auto white balance circuitry. Fortunately, the SX40 delivers well in this category. In all except the trickiest indoor lighting situations the camera did a good job of estimating the lighting conditions and providing a reasonable white balance. For scenes which are partially sunlit and partially in the shade it picked an intermediate value, similar to a "cloudy" setting.

Auto White Balance, 5500k fluorescent light

The relatively small sensor on the SX40 shows itself as increasing noise as we increased the ISO in our studio test shots. You can see from the cropped versions that at ISO 100 and 200 the image detail is excellent, but at ISO 400 not only is a little noise visible, but the noise reduction in the camera has reduced the sharpness of the image a little. For a casual print ISO 400 is still fine, and even ISO 800 is probably okay, but neither would look tack sharp or crystal clear in an enlargement.

ISO 100	ISO 100, 100% crop
ISO 200	ISO 200, 100% crop
ISO 400	ISO 400, 100% crop
ISO 800	ISO 800, 100% crop
ISO 1600	ISO 1600, 100% crop
ISO 3200	ISO 3200, 100% crop

Of course ISO 1600 and ISO 3200 show even more noise and reduced sharpness, so those speeds are really only usable when there is no alternative or you're only going to be using the image for a small space on the web or perhaps a small "snapshot" print.

Additional Sample Images