To measure and compare the Canon EOS 400D / Rebel XTi's noise levels we photographed the standard Gretag Macbeth ColorChecker with it and a number of rival models at each of their ISO settings.

The crops are taken from the original images and presented here at 100%. To compare typical noise in skies and dark shadows the crops were taken from patches 3 and 24 respectively.

Up to 400 ISO, the Canon EOS 400D / Rebel XTi essentially matches the low noise levels of the EOS 350D / Rebel XT. At 800 and 1600 ISO, the 350D / Rebel XT appears to enjoy a fractional advantage here, but it's virtually unnoticeable in practice.

It's also important to note we have compared 100% crops from each camera here. Since the Canon 350D / XT has a lower resolution sensor, its crop therefore represents a slightly larger area relative to the others. As a consequence, any artefacts visible on the 350D / XT crops would be slightly larger and more obvious than the other models here if each image was reproduced at the same physical size. With this taken into consideration, it would be hard to tell any difference between prints made from the two Canons at 1600 ISO, even though the EOS 400D / Rebel XTi result appears very slightly noisier here.

In terms of its 10 Megapixel rivals, the EOS 400D / Rebel XTi delivers essentially the same results as the more expensive Nikon D200 at 200 ISO and above, while arguably enjoying a smoother image at 100 ISO. Interestingly, the Sony Alpha A100 exhibits noticeably higher noise than any of the other models here, especially at 800 ISO and above.

The bottom line is Canon may have increased the resolution of the 400D / XTi, but its noise levels remain very low and usable even up to 1600 ISO. As before though, it's important to compare real-life noise tests as seen on the following page.