Canon PowerShot SX40 HS: Performance

PERFORMANCE
The DIGIC 5 makes the SX40 a snappy performer overall, with responsive controls and displays. Shutter lag is very small, although we go over our concerns with the auto-focus system in the Shooting Performance section.

Shooting Performance
The SX40 offers a high speed burst shooting mode, called High Speed HQ mode. The high speed burst mode is closely coupled to the camera's scene modes. To activate it you turn the mode dial to SCN and use the rear menus to set "HQ." The utility of the High-speed mode is unfortunately reduced because the camera locks focus on the first image. So if you are trying to track a moving subject the later images in the burst are likely to be out of focus.

Shutter Lag (press-to-capture, pre-focused)

Camera	Time (seconds)
Kodak EasyShare Z990 Max	0.01
Nikon Coolpix P500	0.01
Fujifilm FinePix HS20 EXR	0.01
Canon PowerShot SX40	0.02

AF Acquisition (press-to-capture, no pre-focus)

Camera	Time (seconds)
Nikon Coolpix P500	0.30
Fujifilm FinePix HS20 EXR	0.33
Kodak EasyShare Z990 Max	0.38
Canon PowerShot SX40	0.46

Continuous Shooting

Camera	Framerate*
Kodak EasyShare Z990 Max	12.0 fps
Nikon Coolpix P500	10.0 fps
Fujifilm FinePix HS20 EXR	4.1 fps
Canon PowerShot SX40	2.3 fps

*Note: Continuous shooting framerates are based on the camera's fastest full-resolution JPEG continuous shooting mode, using the fastest media type available (300x CF, SDHC, etc.). "Frames" notes the number of captures recorded per burst before the camera stops/slows to clear the buffer.

Perhaps because of the large zoom range and relatively small maximum aperture the camera's auto focus performance was a little spotty. For example attempting to focus on very close objects - from one to three feet - often caused the camera to hunt back and forth and refuse to lock onto the subject. In our tests it actually focused more slowly than its predecessor the SX30.

There are a variety of autofocus modes - not necessarily an advantage as it means that the user is responsible for setting the right one for each situation, defeating some of the point of a simple, integrated camera. The first setting, AF Frame Mode, controls how the camera chooses the portion of the frame on which to focus. You can set it to Flexizone, where you set the size and position of the focus area, or Face Detect, or Tracking AF where the camera will attempt to keep focus on a moving object.

The image stabilization system trumpets six different modes, which is enough to make most people's eyes glaze over. Fortunately there is an "intelligent" IS mode which lets the camera select the appropriate one of the six modes for each shot. In my testing the default mode worked extremely well, as you can see from the 840mm hand-held images accompanying this review.

Canon advertises the camera as useful for photographing wildlife so I took it over to the local lake to give it a test. Certainly the zoom range is more than adequate, with 840mm being the equal of an ultra-high end 600mm lens on a typical DSLR - most of which have a 1.5 focal length multiplier due to their sensor size. And since a DSLR plus 600mm lens would set you back $10,000 the prospect of sub-$500 alternative is certainly appealing! For perching birds like this Great Blue Heron the SX40 produced excellent images:



The camera didn't fare as well with moving subjects. Even with the new Tracking auto-focus feature it was difficult to get the camera to focus on any flying bird or quickly moving animal.

Closer to home a mule deer buck conveniently appeared in our yard and made for a great test subject. He was silhouetted in a very tricky combination of light and shade which the SX40 handled like a champ. All I needed to do was turn the camera's mode dial to "Sports" to get a nice, high shutter speed of 1/400th and fire away.



Lens Performance
The zoom range of the SX40 lens dwarfs all its other specs. Physically measuring 4.3mm to 150mm, it has the same field of view of an equivalent 24mm to 840mm lens for a full frame (traditional 35mm) camera. That range forces a trade-off in maximum aperture so the lens has a mediocre f/2.7 aperture at the wide end and a weak f/5.8 at the long end. This affects AF performance especially at the long end and also limits your ability to isolate a subject from the background by shooting wide open.

The lens uses Canon's UD (Ultra-low Dispersion) glass to provide excellent image quality for an ultrazoom. One difference between the SX40 and a DSLR which may not be obvious at first is the way the zoom is controlled. The SX40 uses the traditional point and shoot system of a level near the shutter button for zooming, while DSLRs rely on the user to turn the zoom ring on the lens. If you are attempting to use the LCD to focus the lever has some advantages, as you can steady the body of the camera with both hands. But for serious use it is awkward to have to keep taking your finger off the shutter button to adjust the zoom. So for high-performance shooting situations a true DSLR will provide a performance advantage.

One difference from the SX30 is that there is no integrated lens cover. Instead the camera relies on a snap-on lens cap, the same way DSLRs do. Like the SX30 there are several focal lengths marked on the lens barrel so you can tell how far you've zoomed. For a lens with this zoom range distortion is remarkably minimal, as shown by these images of buildings on the Stanford campus:

At wide and typical focal lengths the integrated lens is quite sharp, even in the corners. Zoomed in, it is a little soft compared to higher end dedicated zoom lenses, but that is to be expected for a compact ultrazoom. Frankly with the relatively slow aperture of f/5.8 at the long end motion blur will be a bigger issue than lens sharpness for most users needing to zoom way in on a scene. And the camera's relatively slow shutter lag, compared to similarly priced cameras, make it less than ideal for serious action photograph. The good news is that under all these conditions the corners of the image hold up quite well, without any major light falloff, at least after they have been processed by the camera into JPEGs.