To compare noise levels under real-life conditions we shot the same scene using the Canon EOS 350D / XT and EOS 5D within a few moments of each other using their best quality JPEG options, and at each ISO setting. The 350D / Rebel XT was fitted with the EF-S 17-85mm while the 5D was fitted with the EF 24-105mm, both adjusted to capture the same field and set to an aperture of f11 in Aperture Priority mode; f11 was necessary due to the high brightness of the scene.

The image left was taken with the Canon EOS 350D / XT at 100 ISO using the EF-S 17-85mm lens at 26mm f11 (42mm equivalent); the original JPEG measured 2.91MB. The crops are taken from an area just below and to the left of the centre.

Canon’s digital SLRs are known for their low noise performance and the EOS 350D / XT and EOS 5D certainly don’t disappoint. Both deliver very clean results up to 400 ISO with few artefacts and little or no loss of detail. Interestingly the 5D’s 50 ISO result give the impression of applying greater sharpening than at 100 and 200 ISO – this is most apparent in the foliage and fencing.

At 800 ISO and above, noise increases on both models, especially in terms of chroma levels. As expected though, the 5D’s samples suffer less in this regard than the 350D / XT, and its 1600 ISO mode is much more usable than most DSLRs. Noise levels have become quite clear at 3200 ISO on the 5D, but for smaller reproductions, it’s still reasonable.

As on the previous page, it’s important to note we have compared 100% crops from each camera, this time measuring 282x136 pixels. Since the Canon 350D / XT has a lower resolution sensor, its crop therefore represents a larger area relative to the 5D. That is, any artefacts visible on the 350D crops would be larger and more obvious than the 5D if each image was reproduced at the same physical size. In contrast, the 5D's artefacts represent a smaller area, so would be less obvious on images reproduced at the same physical size.

To compare the effect of in-camera processing and compression, we took the 100 ISO sample in JPEG plus RAW mode, and have compared both files for each camera below. We used Adobe Camera RAW with its default settings and white balance 'As shot'; the image was transferred to Photoshop with 8-bits of data before being cropped and saved using the same settings as the JPEGs above.

Both cameras reveal finer detail in their RAW conversions, and again this is most obvious in the foliage and fencing posts. The bare tree branches in the lower left of the 350D / XT crops are also much better defined on the RAW samples. These results prove there’s visible benefits to shooting in RAW with either camera.