A few new features have also popped up with the 40D. Most notably, it offers a Live View mode, with a better, more flexible implementation than that of the 1D Mark III -- or most others, for that matter. Unlike its big brother, you can autofocus in Live View; when you press the AF-ON button, it flips the mirror down, focuses, then flips the mirror back up so the focus-corrected view appears on the screen. On the downside, it focuses only using the centre AF area. And regardless of focus mechanism, it uses only evaluative metering.
As with a point-and-shoot camera, you can pull up a magnified view to help with manual focusing. In addition, three so-called 'silent shooting' options allow you to control the shutter curtain reset to delay the noise and minimise vibration. Though hardly 'silent', the 40D does have one of the quieter Live View modes we've encountered. You can also set the metering timer, how long the camera holds and displays the metering information after you release the shutter button, anywhere from 4 seconds to 30 minutes. We'd love this feature to be available for general shooting rather than limit it to Live View.
All that said, Live View shooting continues to be a bit of a niche application for dSLRs; generally, it's suitable only if your subject matter allows for a tripod and optimally a connected PC for remote control. Keep in mind that the sensor can become warm in this mode, and as Canon warns, increased heat will result in increased image noise.
For more quotidian changes, the 40D now supports Auto ISO in all modes beyond full Auto, which comes in handy every now and then. The new viewfinder system supports interchangeable focusing screens and, for all you four-eyed photographers, offers a relatively high 22mm eyepoint and slightly greater magnification than that of the 30D, 0.95 versus 0.9. Canon also added an sRaw format, which shoots small, 2.5-megapixel raw images. We don't see the point of this feature, but it's easy enough to ignore. Not so easy to ignore is the increased spot size for the spot meter, up to 3.8 per cent of the viewfinder from the 30D's 3.5 per cent.
Other features -- and the 40D has plenty -- remain pretty much unchanged. These include three nine-point autofocus modes: Single-shot, AI Servo tracking autofocus, and AI Focus, which switches between Single and AI Servo if it detects that the subject has moved. Unfortunately, the AI Focus can't tell the difference between subject movement and the photographer doing a focus-and- recompose, so you're usually better off picking Single or Servo and sticking with it. Four metering modes -- evaluative, partial metering (approximately nine per cent of the viewfinder), the aforementioned 3.8 per cent spot, and centre-weighted average metering -- provide reasonable flexibility.
It's got a full slate of white-balance settings, including bracketing and custom corrections along the blue, amber, magenta and green axes; colour temperature; and manual. A few scene program modes -- portrait, landscape, macro, sports and night portrait -- augment the semimanual program, aperture- and shutter-priority, automatic depth-of-field AE, and manual exposure modes. Relevant maximums include a top shutter speed of 1/8,000 second and top flash sync speed of 1/250 second.
Though the 40D isn't missing any feature in particular -- though we could make a case for mechanical image stabilisation -- one feature we'd really like to see trickle down from the 1D series, and which we think makes a lot of sense in a camera of this class, is the ability to define acceptable ranges for aperture, shutter speed and ISO sensitivity when shooting in one of the exposure-priority modes.