Canon EOS Digital Rebel XTi Digital Camera Review
Canon EOS digital rebel xti, CMOS sensor, picture styles, dust removal, DIGIC processor
Testing / Performance
We test cameras' color accuracy by photographing an industry-standard GretagMacbeth color chart, and analyzing the result with Imatest software, which is the leading tool for testing digital cameras. The chart is made up of 24 squares of color. In our tests, we reward color accuracy – the closer a camera comes to reproducing the chart's color exactly, the better it does. Many manufacturers boost saturation and flesh tones, sacrificing accuracy for splashy, flattering color.
We show two Imatest charts to illustrate each camera's color performance. The first is a modified version of the camera's image of the chart. Imatest superimposes a smaller square inside each patch, showing the ideal color adjusted for luminance, and a vertical rectangle of the ideal color.
The second chart shows a color space. Each small square plots the point on the chart where one of the GretagMacbeth patches ought to appear. The square is linked by a line to a circle, showing the point representing the XTi's color rendition. The length of the line indicates the amount of error in the Rebel's color. The middle of the chart is completely unsaturated – that's where the white, gray and black patches belong. The colors are progressively more saturated toward the edges of the chart. So, if the circle is closer to the middle than the square, the XTi undersaturated the color. If the circle is on a line clockwise or counter-clockwise from the square, the hue is wrong.
We tested the Canon Rebel XTi in its "Faithful" picture style, and we set color balance manually. Canon says the Faithful style optimizes color accuracy, and the XTi's performance is excellent. Its saturation score is 100.3 percent – very close to perfect. Its 5.45 mean color error is better than the more-expensive Canon EOS 30D. It's rare for a camera to do as well as the XTi on this test.
Still Life Scene
Click on the image above to view the full res. file
We test resolution and sharpness by shooting an ISO resolution chart designed for digital cameras, and running the images through Imatest software. We shoot at a variety of focal lengths and apertures, looking for the camera's best performance. The Canon Rebel XTi did best at f/10 and 22.28mm and did well compared to the competition.
Click on the chart above to view the full resolution image
Imatest reports resolution in line-widths per picture height (lw/ph), a measure that's independent of the camera's sensor size, and therefore comparable from camera to camera. The Canon Rebel XTi resolved 1531 lw/ph horizontally with 18.6 percent undersharpening, and 1662 lw/ph vertically, with 17 percent undersharpening. With optimal sharpening, done in post processing, or in-camera, its results ought to be very crisp.
Noise – Auto ISO(4.2)
Our test for noise at the auto ISO setting is run just the way our manual ISO test is done. To an extent, it depends on the camera's metering system, because the meter reading influences the algorithm used to set ISO automatically. Because the Canon Rebel XTi lacks a spot metering mode, the camera set the ISO high when we shot the chart against a black background. The auto noise result is roughly equivalent to the XTi's performance at ISO 600. That's a high ISO for this test, but because the camera does well on noise even at high ISOs, the final result isn't that bad.
Noise – Manual ISO(11.49)
Image noise is the electronic equivalent of grain in film or static in a radio signal – it's simply stuff that interferes with the real data. Noise increases as ISO rises on any camera, but the XTi's noise starts relatively low and increases relatively slowly. It has a noise reduction setting, which shows a good effect above ISO 800. Imatest generates our test results by analyzing our shots of the GretagMacbeth chart.
We shot our low light tests with the Canon Rebel XTi set to ISO 400, and adjusted the shutter speed for exposures at 60 lux which is just enough to be comfortable for reading; 30 lux, which is like a gloomy basement; 15 lux, which is like the light from a few candles; and 5 lux, which is very dim.
Low light images were shot at ISO 400, adjusting just the shutter speed to see how the Canon Rebel XTi handles long exposures. As with any camera, we see increasing noise with longer exposure, and decreasing saturation, but the XTi does very well, compared to other cameras. First, it controls noise better than many DSLRs. Second, it maintains color better than others. Even at 5 lux, its colors , though muted, look accurate. The XTi doesn't suffer big color shifts in long exposures, which is a common problem.
Our dynamic range test measures a camera's ability to render detail over a range of subject luminosity. Digital images have a limited range of brightness, but the visible world has an effectively unlimited range, from the dark side of a coal scuttle to the surface of the sun. We test cameras by photographing a Stouffer test chart, which is a calibrated series of patches of gray, reproduced on film and lit from behind. Imatest software analyzes the images, yielding ranges in EV. The high-quality range has a noise level up to 0.1 EV, and the low-quality range has noise up to 1 EV. The low-quality range is important because it indicates whether there will be texture in the brightest highlights and darkest shadows.
The Canon Rebel XTi performs very well in our test. Both high and low quality are excellent at ISO 100. They drop significantly at 200, but both are still good scores. At 400 through 1600, the XTi retains excellent range.
Speed / Timing
Start-up to First Shot (9.46)
The Rebel XTi started up and took a shot in an average of 0.54 second. That's much quicker than most compact cameras, but not outlandishly fast for a DSLR. Still, most users won't be cramped by waiting less than half a second for the Rebel XTi to start up.
Shot to Shot Time (9.62)
The Canon Rebel XTi shot 2.7 frames per second for 69 shots. Though its rate isn't unusual, the length of the burst is remarkable, considering that it shoots 10-megapixel files. This speed may well open up new shooting opportunities for many users – particularly the opportunity to buy large enough Compact Flash cards to hold multiple bursts of 10-megapixel files.
Shutter to Shot Time (8.64)
The Rebel XTi took 0.18 second from the time we hit the shutter until the exposure was made. Focusing accounts for most of the delay, so users can do better by pre-focusing when possible.
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