Canon EOS 450D / Rebel XSi: what's changed

12 megapixel CMOS sensor
The 450D features a new, 12.4 megapixel sensor. It has 12.2 million effective pixels. Further down the line, the A/D converter is capable of relaying 14 bit information to the camera's image processor or as a 14-bit RAW file. This should, in theory at least, offer smoother gradation steps in the final images.

SD / SDHC Card
This is also the first entry-level Canon DSLR to use the Secure Digital format. It's a popular format with the compact digital camera owners Canon will be hoping to lure into DSLR ownership. SDHC is now available in similar sizes and speeds to the CF format used by the 300D, 350D and 400D.

Larger viewfinder
A big step forwards for Canon's entry-level DSLR is the larger viewfinder. It's unlikely to be as bright as the ones found in Canon's XXD models because it uses mirrors, rather than a glass prism but in terms of magnification (size), it's almost on a par with the 30D which was a considerably more expensive camera. It's unusual to see viewfinder specs mentioned when comparing DSLRs but they can make a really big difference to usability.

Spot metering
A regular criticism of Canon's Rebel range has always been the lack of a spot metering mode. Spot metering is a tool that many photographers find invaluable, particularly when setting manual exposures in difficult-to-capture high contrast scenes. Previously only available on XXD-level cameras, we're delighted to see spot metering appear on the 450D (central 4% of the frame).

3" LCD
One of the most obvious external differences between the 450D and its predecessor is the inclusion of a huge 3 inch LCD screen. It's got the same number of pixels as the one on the 400D (which means it's actually lower resolution), but, considering it doubles as the camera's settings screen, the extra size should be useful.

Auto Lighting Optimizer
A feature that is starting to appear on the majority of DSLRs being announced is something along the lines of Canon's 'Auto Lighting Optimizer.' This processes photos after they've been taken to try to correct contrast and brightness to optimize the image.

High ISO noise reduction
Another feature trickling down from the 40D is the option to add an extra level of noise reduction when shooting at the camera's highest sensitivity settings. Comes at the expense of continuous shooting speed so has been made optional.

Improved 9-point AF system
Although we've not had a chance to test the changes, Canon is claiming the AF system has been revised in the XSi / 450D. Certainly the AF chip appears to be different to the one we showed in the 400D review.