Canon EOS 20D - What's new / changed

8.2 megapixel CMOS sensor
The first and probably most significant change is an all new 8.2 megapixel CMOS sensor which has the same dimensions (albeit for half a mm) as the EOS 10D's six megapixel CMOS sensor. Canon also claims improved sensitivity thanks to new microlenses and a new on-chip 'noise elimination circuit', frame rates are up as this sensor has a 4-channel read-out (double the EOS 10D).
Near instant power on time
It makes a big difference, the EOS 10D typically took 2.5 seconds to start up and be ready to shoot, the EOS 20D takes just 0.2 seconds (verified).
5 fps continuous, 23 frames
Up from 3.3 fps (frames per second) and a maximum of 9 frames the EOS 20D can shoot continuously at 5 fps for up to 23 frames (JPEG).
All-new 9-point AF system
The EOS 20D gets an all new (not seen on any other SLR) nine point AF system which has its AF points in a diamond pattern. It's quite noticeably faster than than the EOS 10D and has better low light working range (-0.5 EV compared to 0.5 EV). Note that the center point is a 'cross type' sensor when used with lenses with a maximum aperture of F2.8 or faster.
DIGIC II processor
Canon's DIGIC processor has been the key to consistent image quality across their range, the new DIGIC II processor first seen in the EOS-1D Mark II is now used in the EOS 20D.
Support for EF-S 'digital lenses'
Just like the EOS 300D (Digital Rebel) the EOS 20D now supports the new Canon EF-S 'digital' lenses which have the same lens mount as EF but have a rear element closer to the sensor and can be made smaller as they only need an imaging circle large enough to cover the APS-C size sensor. This also means the EOS 20D's mirror is smaller than the EOS 10D.
Faster top shutter speed
The EOS 20D's fastest shutter speed is 1/8000 sec compared to the EOS 10D's 1/4000 sec.
Faster X-sync shutter speed
Flash sync speed has also been increased slightly to 1/250 sec compared to 1/200 sec on the EOS 10D.
Modified parameter sets
Canon has split color space from parameters and introduced two preset parameter sets, the default being Parameter 1 which has a higher contrast, saturation and sharpness than the default on the EOS 10D.
Black & White mode
Also new is an in-camera black and white mode with digital color filters which work in the same way as a color filter would on black and white film. Additionally you can also apply a 'tone' to the black and white image (sepia etc.)
Separate color space selection
As noted above color space has now been split away from parameters which means you can now combine parameter adjustments with Adobe RGB color space.
True RAW + JPEG support
While the EOS 10D claimed RAW+JPEG support, in reality only provided a JPEG embedded into the RAW file. The EOS 20D now has 'proper' RAW + JPEG and in this mode writes one RAW (.CR2) and one JPEG (.JPG) file for each frame taken.
New WB shift / WB bracketing screen
The EOS 20D's white balance shift now provides shift in two axes; Blue to Amber and Magenta to Green. WB shift is achieved on this new screen using the new joystick controller and you can add bracketing by simply turning the quick control dial.
Control of Long exposure NR
The EOS 20D now allows you to disable long exposure noise reduction (dark frame subtraction) and Canon claims even better long exposure performance than the 10D.
Menu hints
The EOS 20D menu now includes a few simple 'hints' to remind you that the setting change you just made won't take effect unless you put the camera in the correct mode.
Record review histogram via INFO button
On the EOS 10D you chose the record review display mode from a menu option, on the EOS 20D you simply press the INFO button during record review to change the display mode for all subsequent record review displays.
USB 2.0 Hi-speed connectivity
Direct USB transfer of images from the EOS 20D are now a much more viable option thanks to the introduction of Hi-speed USB 2.0 interface. We achieved transfers of just over 3.0 MB/sec.
PictBridge direct printing support
Pretty much standard on any modern digital camera but noteworthy anyway, the EOS 20D now supports PictBridge direct USB printing as well as Canon's own direct printing to Canon printers.
Support for DVK-E2 data verification kit
The EOS 20D becomes an option for law enforcement and any other industry which requires verification of image authenticity. The camera can now embed a unique encrypted signature into each image which enables them to be later verified using the DVK-E2 kit for authenticity.
New BG-E2 battery grip
Because of its slightly smaller dimensions the EOS 20D gets a new battery grip. The BG-E2 supports two Lithium-ion battery packs or six AA batteries (using a supplied battery magazine).
Slightly smaller and lighter
The EOS 20D shaves 6 x 2 x 3 mm from the EOS 10D's dimensions and is more impressively 105 g (3.7 oz) lighter (approximately the weight of the battery).
Higher pop-up flash
The EOS 20D now has a flash which raises considerably higher than the EOS 10D, it now has a claimed FOV coverage of 17 mm. It also uses E-TTL II flash metering which utilizes lens distance information to improve flash power calculation.
Smaller mirror & new focusing screen
To add support for EF-S lenses the entire mirror box and mirror are smaller compared to the EOS 10D (click here for a diagram). In addition the 20D has a new 'Precision Matte' focusing screen which has a more neutral color response and is better for manual focusing.
CF activity light moved
The CompactFlash activity light has moved from the edge of the compartment door to a position just to the bottom corner of the quick control dial.
Flush connectors cover
A subtle improvement but the rubber covers over the connectors on the left side of the camera are now 'almost' flush to the camera body.
Combined power & quick control dial lock
Canon has combined the power switch and the quick control dial lock to a single switch.
New multi-controller 'joystick'
Just above the quick control dial is a new eight way multi-controller which also has a 'click' press. This control is used for AF point selection, WB shift and panning in play magnification.
Updated menu design
Although not a significant change the EOS 20D's menus now reflect the newer appearance seen on the PowerShot series. The menu also indicates that you can use the JUMP button to skip to the next menu section.
Backup battery moved to compartment
The backup battery has changed to a CR2016 and has moved from the base of the camera to a slot inside the battery compartment.
Embossed Canon logo
Last but perhaps not least, the Canon logo on the front of the camera is now embossed into the body surface, it's a nice touch.