Canon EOS Digital Rebel XT Digital Camera Review

by Alex Burack
Published on June 01, 2005

Navigation
Intro	Testing / Performance
Physical Tour	Components
Design / Layout	Modes
Control Options	Image Parameters
Connectivity / Extras	Overall Impressions
Conclusion	Specs
Photo Gallery

Color (8.36)
When converting to the digital format from film, many photographers are skeptical of the color reproduction capabilities of digital cameras. While digital prints will often exhibit an impressive color range, there is often a variance from the natural scene. For many digital cameras, the tendency is to over-saturate colors, increasing the vibrancy of the scene. This can make the image appear more striking, but is certainly not a realistic representation of the setting. When we test the color capabilities of digital cameras, we are evaluating the accuracy on the reproduced tones. Since anyone can alter the tonal values on a digital image using a software application, we determine the camera’s ability to record the scene.  

To test the color accuracy of the Canon Digital Rebel XT, we recorded several exposures of the industry standard GretagMacbeth color chart. The images were then imported into Imatest Imaging Software, to contrast the camera’s produced colors with the original colors on the chart. The chart below displays the results. For each color tile, the outer squares show the XT’s recorded colors, while the inner square depicts the color corrected version (approximating an auto corrected version in a computer application) and the small, vertical rectangle in the center is the tonal ideal.

The chart below displays the same color information as above in a more direct manor. The circles represent the colors produced by the digital Rebel XT; the squares represent the ideal colors from the GretagMacbeth chart.

According to our test, when shooting with the Digital Rebel XT at ISO 100, the camera will oversaturate tones by 115% with a 7.17 mean color error. This is a bit surprising, as a 115% mean saturation score means the tones are heavily embellished. This might not be as dire as it sounds, as again, many people’s eyes tend to prefer the look of rich red values and deep greens to their natural tone. However, for those who seek a straight realistic representation of the scene, it might be difficult to attain using the Digital Rebel XT. Nevertheless, the produced images contain remarkably rich tones that would likely be preferred by many users.

Still Life Scene
Below is a shot of our favorite still life scene, photographed with the Canon Rebel XT.

Click on the above image to view a full resolution version (CAUTION: The linked image is very large!)

Resolution / Sharpness (7.10)
Some recent film converts making the pilgrimage to the digital SLR realm are still struggling with dated questions like “are 8.0 megapixels really necessary for any ‘serious’ photographer or is it overkill?” To determine how much resolution is appropriate, users should recognize that the decision generally boils down to the photographer’s printing needs, balanced with their allotted budget. For users who do not foresee printing larger than letter-sized (8.5 x 11 inches), you really don't need more than 4 or 5 megapixels. A 6.0 megapixel DSLR will make stunning, razor-sharp letter-sized prints and respectably sharp 13 x 19 inch prints (the largest you can print on consumer printers). You can crop considerably and still get excellent letter-sized prints; however, if you plan to print large, the Rebel XT will give you an edge. 13 x 19 prints made from the XT will appear superior to 6.3 megapixel images recorded with the Nikon D70, while providing the added opportunity to go even larger and maintain good image quality.

 
Click on the above chart to view a full res. image

We test each camera’s resolution to determine exactly how many pixels are being used to form the image. This is done by recording a series of exposures of a resolution chart, and then importing the images into Imatest Imaging Software to analyze the results. When this is conducted, cameras that use 70 percent of their advertised pixels are considered “good,” while 80-89 percent is deemed “very good,” and anything exceeding 90 percent earns an “excellent” designation.

The Canon EOS Digital Rebel XT relies on an 8.0 megapixel, single-plate CMOS color sensor. The sensor utilizes a fixed position low-pass filter as well as a RGB primary color filter to create images in a 3:2 aspect ratio. Our tests concluded that the Rebel XT uses 7.102 of its 8 megapixels; that’s approximately 89.2% of its advertised resolution and a near excellent score. This is nearly identical to the original Rebel’s 89.8% score, but still includes nearly 1.45 more megapixels per image. We report the highest resolution detected for each camera. The highest resolution value we attained with the EOS Digital Rebel XT was shot with the camera’s kit lens set to f/11 at a focal length of 33mm.

Noise Auto ISO (3.9)
Although the Digital Rebel XT offers a limited sensitivity range when shooting in the Auto ISO setting, there will be many users who rely on it. When we tested the produced noise with the ISO set to Auto, the results were disappointing. Unlike the camera’s ability to reduce noise when the ISO was set manually (below), the Rebel XT displayed difficulties in the Auto mode. This is common of many compact digital cameras, as the problem generally stems from the camera’s inaccurate setting of the sensitivity rather than an inability to suppress noise. The Rebel XT fell into this same old trap, earning a dismal 3.9 overall Auto ISO score and producing images that were on par with the camera’s manual noise output at ISO 400. This is a bit disconcerting as the tests were conducted in a fixed studio setup with the light levels exceeding 400 Lux. The Rebel XT should have recognized this and reduced the ISO value to 100 or 200. For optimal quality, users will have to set the sensitivity themselves.

Noise Manual ISO (11.53)
The pixel configuration on the XT’s sensor has been redesigned to maximize sensitivity and minimize distortion. The photodiode or light sensitive portion beneath each microlens has also been directly enhanced to reduce the signal amplification necessary to attain a detailed exposure. Additionally, the microlenses themselves have been enlarged, though the size of the pixels has been reduced. The increased lens area will attract more light to each individual pixel, minimizing the vacant space between microlenses and creating more sensitized surface to absorb information. This is a far more efficient and effective system of information gathering and should significantly improve the camera’s low-light performance. Canon has also applied an on-chip Noise Reduction Circuit to the XT’s CMOS sensor for added noise protection.

To evaluate the Rebel XT’s noise suppression capabilities, we tested the amount of noise output at each available ISO rating, including 100, 200, 400, 800 and 1600. We compiled the results from each test into a regression analysis to determine the overall manual noise score. The Rebel XT’s noise results at each ISO setting are expressed in the chart below, with the available ISO ratings placed along the horizontal axis and the resulting noise plotted on the vertical axis.

The engineering details listed above proved true to form, as the Rebel XT earned an 11.53 overall manual noise score. This is incredibly high and represents a strong ability to control noise. By comparison, the original EOS Digital Rebel scored a 9.01 overall manual noise score. The improvement may be attributed to the addition of the DIGIC II processor, which is designed to more accurately discern the boundaries between adjacent pixels and interpret whether the perceived variance in pixel values is attributed to detail in the image or noise.

Low Light (9.0)
To evaluate the effectiveness of a camera at night or in low light, we test the camera at four decreasing illumination values. The tests are conducted at the camera’s highest ISO value (ISO 1600 for the XT) without the use of the flash. The color is manually calibrated for each lighting setup to evaluate the camera’s highest level of performance. This helps give an idea of how sensitive the sensor is to light and will pinpoint the increments at which the camera loses effectiveness. Cameras are tested at 60, 30, 15, and 5 Lux to approximate performance in common low light conditions; 60 Lux appears to the eye as a typical bedroom illuminated by two small lamps may appear after dark. 30 Lux roughly equates to the illumination give off by a single 40 watt light bulb and 15 and 5 Lux are conditions near darkness.

Low Light Tests
60 Lux	30 Lux
15 Lux	5 Lux

The low light test is a relatively new addition to our reviews; however, the Digital Rebel XT performed well beyond any other model tested up to this point. The XT displayed an ability to maintain strong color representation with distinct tonal definition throughout the test. Once pushed to 5 Lux, there is a bit of a decline in color vibrancy, but colors are still well represented. The camera’s ability to contain noise down to 5 Lux is impressive. Once set to ISO 1600, there is a boost in perceivable noise, but its appearance is subdued when compared to any other camera tested to this point. The camera’s low light capabilities seem to be one of the imager’s strongest attributes, enabling the camera to capture sharp images with nice color representation at night or in minimally lit indoor conditions.

Speed / Timing
Startup to First Shot (9.58)
The Canon EOS Rebel XT advertises a much faster startup time than its predecessor. This proved to be true, with the XT starting up and taking its first shot in an impressive 0.2 seconds.  

Shot to Shot (9.67)
Shutter lag was a significant problem with the original EOS Digital Rebel, prohibiting many potential consumers from taking the camera too seriously. This issue has been corrected on the XT, which now rivals most digital SLRs on the market in this area.  

Shutter to Shot (9.08)
The XT shows its SLR capabilities with hardly any shutter lag. From the moment the shutter release button was pressed to the moment the picture was taken, a mere 0.02 seconds had gone by.