Live View in 40D

The Canon 40D has the ability to flip up the mirror to see what's on the image sensor, live. Canon calls this "Live View" and it's only useful for manual tripod shooting, since autofocus doesn't work in Live View.
If you set a custom function and press the AF-ON button, the mirror flips down (cutting off live view), the 40D autofocuses, and then you can take your finger off the AF-ON button to resume live viewing on the LCD. Yes, you can get some AF in Live View, but no, you can't get them at the same time.
You can magnify the live image by five or ten times to check focus.
Live view adds a grid for helping get level shots.
Live view is also a mirror lock-up and slightly shortens the already minimal shutter delay
Live view also adds two quiet shooting modes, which can happen because the mirror is already up. This is advantageous for remote surveillance, since you can duct tape your 40D someplace it doesn't belong, and with the WFT-E3A wireless transmitter you can see what's going on and fire it from your laptop as you sit in your car . The images are transmitted to your laptop with the 40D not making much noise. If your target sees your 40D, you may lose your camera, but you've got your images and you're rolling before they see you. You also can do this with a USB cable, but it's not as stealthy.

Specifications EOS 40D

Body: Specified as "magnesium alloy exterior," implying the frame is something less exotic.

Finder: 95% linear coverage. 0.95x magnification (50mm lens). Eye relief (eyepoint) 22mm. -3 to +1 diopter. Glass pentaprism, no eyepiece shutter.

AF: 9 cross points, work up to f/5.6. (Same points as 20D and 30D, but otherwise completely new.) Auto and manual selection. The central point offers extra precision at f/2.8 in both cross directions, a first in any Canon. Canon claims the "AF calculation speed" is 30% faster than the 30D, but that's fluff, since the calculation speed is only one part of many processes involved in the AF system.

Flash Metering: E-TTL II, identical to the 20D and 30D. New wireless remote control of the settings of the 580EX II.

Built-in Flash: Yes, covers 17mm lens, GN 13m/43' at ISO 100.
Maximum Shutter Speed with Flash: 1/250, normal sync
Shutter: 30s - 1/8,000.

Shutter Death: Tested, but not guaranteed, to 100,000 cycles. I suspect if you can kill it under warranty, you're covered regardless of how many frames you get off.

Frame Rate: 6.5 FPS. The shutter and mirror have separate motors.

Buffer Depth: 75 JPG or 17 raw

Image Sensor: 10.1MP CMOS, 1.6x crop factor, made by Canon. 22.5 x 15.0mm. 14-bit A/D conversion, suggest better high ISOs and lower noise.
Ultrasonic Sensor Cleaner.

Image Sizes: 3,888 x 2,592 native, also 2,816 x 1,880 (M) and 1,936 x 1,288 (S). Raw comes in your choice of 3,888 x 2,592 (raw) and 1,936 x 1,288 (s-raw).
ISO: 100 - 1,600 (ISO 3,200 turned on in a custom function).

LCD: 3," 230,000 pixels. a 3" LCD has 20% less linear resolution. In simple English, this 3" LCD shows the same detail and information as today's 2.5" LCDs, just bigger.
Storage: Compact Flash types I and II. with optional WFT-E3A you can plug in a USB hard drive and record to it.

Power: BP-511A rechargeable lithium-ion and CG-580 charger, same as 30D, 20D
Size: 5.7 x 4.2 x 2.9" W x H x D, (145.5 x 107.8 x 73.5mm), rated.

Weight: 26.1 oz (740g), rated, usually stripped of battery, card, lens, etc.

Canon EOS 40D Preview

The EOS 40D becomes the sixth Canon 'prosumer' digital SLR, a line which started back in 2000 with the EOS D30, and how far we've come. It's been eighteen months since the EOS 30D and although on the surface the 40D looks like a fairly subtle upgrade there's a lot that makes this an even better camera. Of course we expect a step up in megapixels, and so the 40D comes with a ten million pixel CMOS sensor with the same sort of dust reduction as the EOS 400D, an ultrasonic platform which shakes the low pass filter. Other improvements bring the EOS 40D closer into line with the EOS-1D series, these include a move to the same page-by-page menu system, both RAW and sRAW (2.5 MP), 14-bit A/D converter and 14-bit RAW, cross-type AF points for F5.6 or faster lenses, a larger and brighter viewfinder, interchangeable focusing screens, a larger LCD monitor (3.0") and faster continuous shooting (6.5 fps).

Canon EOS 40D PreviewPhil Askey, August 2007

What's New in EOS 40D

-10MP up from 8MP, insignificant.
-6.5FPS up from 5FPS, important for action.
-New AF sensor. Same number of sensors, but better sensors.
-3" LCD up from 2.5 in 30D.
-Better weather sealing.
-Built in sensor cleaning like the eos 400d