Canon EOS 40D Exposure

The Canon 40D provides as little or as much exposure control as you could want. Standard exposure modes include the usual Program, Aperture-Priority, Shutter-Priority, and full Manual modes, as well as some "Image Zone" (scene-based preset) modes, an Automatic Depth-of-Field mode, and three Custom modes, which users can program for quick access to their favorite functions. The "Image Zone" exposure modes include Portrait, Landscape, Close-up (macro), Sports, Night Portrait, and Flash Off modes. These modes preset a variety of camera parameters to make it easier for non-expert photographers to achieve good exposures in a variety of standard shooting situations. The Flash Off mode simply disables the flash and external Speedlite (if attached), and puts the camera under automatic exposure control. The full Auto mode takes over all camera functions, turning the Canon 40D into a very easy to use point-and-shoot camera, albeit a very capable one.

The Aperture Priority and Shutter Priority modes work much the same as on any other camera, allowing you to adjust one exposure variable while the Canon 40D selects the other for the best exposure. Program mode keeps both variables under automatic control, while Manual mode gives you full control over everything. The Automatic Depth-of-Field mode (A-DEP) uses all nine autofocus zones to determine the depth of field in the active subject area. Once the Canon 40D has determined the range of focusing distances present across the nine zones, it automatically computes the combination of aperture and shutter speed needed to render the nearest and furthest points in sharp focus.

Canon 40D Metering & ISO Options

Here you can see the concentrations of three of the four meter settings. Center weighted is on the left, Partial in the center, and Spot on the right. Spot isn't much different from Partial.

Exposure metering options include Evaluative, Partial, Spot, and Center-weighted options. The Canon 40D offers variable light sensitivity, with ISO equivalents of 100, 200, 400, 800, 1,600, and 3,200 (Hi), or you can set it to move between settings in 1/3 stops (100, 125, 160...).

For adjusting the exposure, the Canon 40D's Exposure Compensation setting increases or decreases overall exposure from +/-2 EV in one-third or one-half EV increments.

An automatic exposure bracketing feature lets you set the total exposure variation (across three shots) at anywhere from +/- one-third or one-half EV all the way up to +/- 2 EV. The nice part is that the automatic variation is centered around whatever level of manual exposure compensation you have dialed in. Thus, you could manually set a positive exposure compensation of 0.7 EV, and then have the camera give you a variation of +/- 2/3 EV around that point.

AE/AF Lock

Another feature deserving comment is the Canon 40D's separation of the autoexposure and autofocus lock functions. In consumer-level digital cameras, half-pressing the Shutter button locks exposure and focus simultaneously. You can use this to deal with an off-center subject by pointing the camera at the subject, locking exposure and focus, and then reframing the picture before finally snapping the shutter. The only problem is that you sometimes need to perform a more radical recomposition of the subject in order to determine the proper exposure. For instance, you may want to zoom in on the subject, grab an exposure setting, and then zoom back out before taking the picture. Situations like that require locking the exposure independently of the focusing, and the Canon 40D provides for just such eventualities by way of a separate AE lock button on the back of the camera, right under your right thumb. Through the Canon 40D's Custom menu, you can specify the operation of the AE Lock button, as well as the AF/AE locking function of the Shutter button. A very handy feature indeed.

AF-ON button

New to the Canon semi-pro series, the AF-ON button, also called AF Start, allows you to set focus before depressing the shutter button. When in Live View mode, which has no default autofocus option, you can press the AF-ON button to have the camera flip the mirror down so it can focus and return to Live View mode. The LCD will be blank momentarily.

With Custom Functions, you can reprogram the behavior of the AF-ON button, as well as switch functions with the AE/AF Lock buttons.

White Balance Options

The Canon 40D offers a full range of White Balance settings, including six presets, an Auto setting, and a Custom setting. The six presets include Daylight, Shade, Cloudy, Tungsten, Fluorescent, and Flash. The Custom setting bases color balance on a previous exposure, meaning you can snap an image of a white card and then base the color temperature on that image. A White Balance bracketing option snaps only one image, then writes three successive files from that single image. Bracketing steps are from -/+ 3 stops in whole-stop increments. (Each stop corresponds to five mireds of a color conversion filter, for a total range of +/- 15 mireds. This corresponds to about a +/- 500K shift at a normal daylight color temperature of 5,500K.)

The WB Bracketing is set on the same grid as the White Balance correction grid. Fairly sophisticated, the white balance correction tool lets you shift the color balance toward more or less green, amber, magenta, or blue, using a +/-9 step grid format. You move a highlighted square through the grid to adjust the color balance. It's a slightly more advanced interface than I'm used to seeing on digital cameras, but a useful one that greatly extends the camera's color corrective abilities.

The Canon 40D also offers a Picture Style option through the LCD menu, which lets you select from Standard, Portrait, Landscape, Neutral, Faithful, Monochrome, or three User Defined settings. In each of the preset modes, the contrast, saturation, sharpness, and tone are set for specific conditions. The three User Defined options let you manually adjust each variable, then save it as a custom parameter. Finally, you can set the camera's color space to sRGB or Adobe RGB.

Continuous Shooting Mode and Self-Timer

The Canon 40D's Continuous Shooting mode is rated by Canon at 6.5 frames per second in high speed mode, for a total of 75 Large Fine JPEG shots or 17 RAW before the buffer fills; or 3 frames per second in low speed mode for a total of 205 Large Fine JPEG shots, or 20 RAW images before the buffer fills. Do note, though, that the number of consecutive shots could be limited by CompactFlash space, if your memory card is nearly full. Also, when shooting JPEGs of a very complex scene with a lot of sharp, fine detail may also compress less and result in lower buffer capacities.

The camera's Drive setting also accesses two Self-Timer modes, which open the shutter 10 or 2 seconds after the Shutter button is pressed, giving you time to dash around in front of the camera. A Remote Control mode works with the dedicated and wireless remote units as well.


The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Canon EOS 40D Photo Gallery .

Not sure which camera to buy? Let your eyes be the ultimate judge! Visit our Comparometer(tm) to compare images from the Canon EOS 40D with those from other cameras you may be considering. The proof is in the pictures, so let your own eyes decide which you like best!

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