Canon recently announced the 4th model in their popular Digital Rebel camera line. The new Rebel XSi gets a bump in resolution over the
Rebel XTi (12.2 megapixel vs. 10.1 megapixel) and a new larger LCD screen - increasing the screen size from 2.5" to 3.0" (see images below comparing the screens).

Canon also added "Live View" which we first saw in the 40D. Live View allows you to use the LCD screen as a viewfinder, although it is mainly designed for use in manual focus mode. If you wish to use Live View with autofocus, it is a bit convoluted and can only work with static subjects. You must hold the camera still, press and hold a button until the camera beeps, release the button and the press the shutter to take the photo. There may be uses for Live View outside the office, but we don't see it being used very often for clinical photography.

There is a slightly faster continuous shooting mode and the XSi uses a more powerful battery which should equate to longer life. The XSi also sees Canon switching from Compact Flash memory cards to SD cards.

One highly recommended accessory is Canon Rebel XSi Battery Grip. The Rebel XSi is smaller than their other cameras and may be a bit too small for larger hands. The optional Battery Grip adds an additional 1.5 inches to the height of the camera as well as offering two different ways to power the camera. The Battery Grip will accept either (2) rechargable lithium-ion batteries or (6) AA (alkaline or rechargable) batteries.

Canon designed the Rebel XSi to be compatible with most of their EOS 35mm camera accessories, including the Canon MR-14EX macro ring flash, Canon MT-24EX dual point flash and the Sigma EM-140DG macro flash. This allows E-TTL (evaluative through-the-lens) flash metering for automatic exposure. Just as you would with a 35mm clinical camera, you simply set the magnification and f-stop and then move towards your subject until the image is in focus - the Rebel XSi takes care of the rest.