Canon EOS Rebel XTi

Manual Control Options
The Rebel XTi offers full manual control of aperture, shutter speed, ISO, white balance, focus and a range of image parameters. Its manual functions are as complete as its automatic ones.

Focus
Auto Focus (7.5)
The Rebel XTi's autofocus system is quick and accurate, and reasonably good in low light. Its 9 sites are arrayed in a diamond pattern that stretches about halfway out from the middle to the edges of the frame. The Canon XTi can be set to One-shot AF, which focuses once when the shutter is depressed halfway; AI Focus AF, which focuses once, but refocuses if it detects subject movement; or AI Servo AF, which continuously adjusts focus.

If there were a single feature we could compare directly between the Rebel XT and the Rebel XTi, it would be autofocus. The XTi seems to work significantly better.

Manual Focus (7.5)
It's hard to leave the frustrations of the kit lens aside for a discussion of manual focus because every time we move the focus ring, the image jiggles. Still, that's clearly a limitation of the cheap lens. The viewfinder screen is bright and contrasty. If the user presses the shutter partially, the autofocus system will confirm focus if detected by lighting up the site in focus and the focus confirmation dot below the image. Because of the relatively low magnification of the viewfinder image, the Rebel XTi is not as easy to focus as the more sophisticated Canon EOS digital cameras.

Exposure (8.5)
The Rebel XTi has 5 manual exposure modes: full manual, program, time-value (shutter priority), Aperture-value (aperture priority), and A-DEP, also known as automatic depth-of-field auto exposure. All the non-exposure settings on the camera can be manually controlled in the manual exposure modes.

Full manual works just as expected, with a meter indicator showing over and underexposure in the viewfinder and on the LCD. The only glitch is that the control dial does double-duty - used alone, it changes shutter speed; in combination with the AE compensation button, it controls aperture. The button must be held down while the dial is turned to change the aperture. Program sets both aperture and shutter speed automatically. In program, the control dial shifts the aperture and shutter combination without changing the exposure value, or, if the AE compensation button is pressed, it adjusts the exposure. In aperture value, users set the aperture with the control dial, and the Rebel XTi sets the shutter speed. With the AE compensation button pressed, the control dial changes the shutter speed to vary the exposure. In time value, the control dial varies the shutter speed, and the camera sets the aperture. With the AE compensation button pressed, the dial changes the exposure value by varying the aperture.

The depth-of-field exposure mode controls both shutter speed and aperture, but it does so with input from the autofocus system. The camera calculates the aperture required to get all of the autofocus points sharp simultaneously, sets that aperture, and then sets the shutter speed to match. The system worked well in our test, using the kit lens.

Metering (6.0)
Some users have moaned for years about how Canons don't have spot meters. The company listened, and put one on the EOS 30D earlier this year. Apparently, that was just a token effort – the Rebel XTi doesn't have one. It has evaluative, center-weighted averaging, and “partial” metering, which measures a sharply-defined circular area with a diameter from the top-center autofocus point to the bottom-center one.

The evaluative system takes several readings across the field of view, compares them, and arrives at an exposure. It should be able to detect backlighting and other tricky lighting. Center-weighted takes a single reading in the whole frame, but is more sensitive at the center of the frame. In practice, the Rebel XTi's evaluative and center-weighted modes gave us very similar, dark results with a backlit subject in the center of the frame, and partial metering performed much better. With a backlit subject to the side, center-weighted and partial both gave unacceptable, underexposed results, and evaluative was much better. It was still not as good as the centered backlit subject in partial mode. Evaluative modes compromised to some extent – it darkened the off-center subject while trying to retain detail in the background.

White Balance (8.0)
The Rebel XTi's presets are Sun, Shade, Overcast, Tungsten, Fluorescent and Flash. It also has an Auto setting. The Rebel XTi's custom white balance setting is like other Canon cameras'. Users must take a shot of something white in the lighting they want a custom balance for, and then have the camera analyze it. The system works well, but it's cumbersome – though it's possible to set the camera to the old custom balance without hitting the menu button, it's not possible to make a new one without the menu. It's a multistep process, and it should be faster.

ISO (7.5)
ISOs from 100 to 1600 are available on the Rebel XTi, in full-EV increments. The camera performs well at high ISO. Still, it would be useful to have 1/3-EV increments in the ISO range. In most cases, it's best to use the minimum ISO necessary, and a full-stop jump isn't always needed.

Shutter Speed (7.75)
The Rebel XTi offers shutter speeds from 1/4000 to 30 seconds with an electronically controlled focal plane shutter. The fastest normal flash sync is 1/200, and the shutter can be set in either ½ or 1/3-EV increments. The XTi also offers a bulb setting for exposures over 30 seconds. The shutter offers every setting a Rebel XTi user needs – there isn't a need for speeds faster than 1/4000, and shooting exposures over 30 seconds with a stopwatch and remote control is accurate enough.

Aperture (0.0)
The Rebel XTi can control aperture settings in 1/2 or 1/3-stop increments, and communicates electronically with EF and EF-S mount lenses. This section presents yet another occasion to note that the kit lens, the 18-55mm, f/3.5-5.6, isn't bright enough at the telephoto end.

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