Canon EOS Rebel XT

Resolution
Armed to appeal to the “serious” photographer, the Rebel XT is equipped with a high-sensitivity, high-resolution, 8.0 megapixel single-plate CMOS color sensor. The sensor utilizes a fixed position low-pass filter as well as an RGB primary color filter to create images of striking definition and sharpness in a 3:2 aspect ratio.

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 actually 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 probably don't need that much resolution. 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 has an edge. 13 x 19 prints are far superior to prints that can be made from 6.3 megapixel images (such as those produced by the Nikon D70), while providing an opportunity to go even larger and maintain good image quality.

The XT’s CMOS sensor and anti-aliasing filter
At 22.2 x 14.8 mm, the 8 megapixel sensor is only slightly smaller than the 22.5 x 15.0 mm 8.3 megapixel sensor of the EOS-20D. It's anybody's guess why Canon chose to use such a close but different size (likely a straight economic decision). The question naturally arises: “Are there any other differences between the sensors?” I'm happy to report that we accidentally stumbled upon one.

When we photographed the Canon representative (above) with the inexpensive but excellent EF-S 18-55mm f/3.5-5.6 kit lens, we found Moire fringing on his shirt below his left shoulder, visible as reddish and greenish fringes in the full magnification cropped image (below, right). Those bands weren't on his shirt!

Moire fringing is a classic interference pattern that can occur when the image contains repetitive patterns with energy above the highest spatial frequency a sensor can resolve (complicated by the Bayer pattern, where red and blue pixels have twice the spacing of green pixels). To control aliasing, most digital SLRs have anti-aliasing filters, which reduce or eliminate this effect, but also soften the image slightly. It's a classic tradeoff, one that involves cost as well. A good anti-aliasing filter increases the manufacturing cost of the sensor.

I've never seen aliasing in my EOS-20D. The presence of the Moire means that the Rebel XT evidently has a weaker anti-aliasing filter. This is likely to make it sharper than the 20D (such a deal!), but at the price of increased susceptibility to Moire. This could be an issue to some photographers, though it rarely bothers most of us.

Whether this is a good or bad thing depends on your photographic style and choice of subjects. A few details:

• Aliasing, which is the cause of Moire, is always present, but Moire itself is only visible on repetitive patterns (window screens, fabrics, occasional architectural details).
• The better the lens, the worse the aliasing. A poor lens acts as its own anti-aliasing filter.
• The Nikon D70 has a weaker anti-aliasing filter than its big brother, the D100. The Rebel XT has the same relationship with the EOS-20D. Neither Nikon nor Canon has explained this. My guess: lower manufacturing cost.
• The above image was shot as a JPEG. Off-camera RAW converters may be able to do a better job of suppressing Moire. It's possible that Moire may not be as much of a problem when shooting RAW.

I wouldn't use the Rebel XT if I were photographing fashion or weddings, at least unless I was sure a good RAW converter would help. Moire on the bridal gown could make for a very unhappy client. And besides, if you want respect from clients you have to carry a camera that looks "professional." The Rebel XT is simply too small to be taken seriously. You need at least a 20D with a battery grip. Of course, if you're taking candids, and you don't want to be taken seriously, the Rebel XT would be the camera of choice.

Speed
Largely questioned for its speed, Canon responded to critics by equipping the Rebel XT with a DIGIC II processor. The improved processor significantly increases shooting speeds and internal controls, while minimizing processing time. The Rebel XT now performs at a rate parallel to other digital SLRs. Shooting at 3 frames per second, the XT will continue in its burst for up to 14 sequential images (best quality JPEG), up from the original Rebel’s 2½ fps rate for only 4 consecutive images.

The XT’s shutter lag has also been reduced to just 100 milliseconds (equivalent to the lag on the EOS-10D), along with providing a near instantaneous boot-up. The 0.2 second start-up speed can be a real asset if an opportunity suddenly presents itself. A necessary response to the original Rebel’s ascribed “point-and-shoot-like speeds,” the XT’s faster configuration will provide a big improvement over the near 3 second turn-on time of the original Rebel.

The XT is also compliant with USB 2.0, enabling high speed output from the camera to an external source. The Rebel XT will now be able to fully maximize the potential of high speed cards currently available.