UPDATE 5/11/2009: after half a year of working pretty well, my AF problems are back. Again all lenses are frontfocusing slightly compared to Liveview, with the kit zoom showing the biggest AF error. I will probably switch back to the 300D and convert the 450D to infrared :(

UPDATE 16/4/2009: three weeks ago I received my 450D back from Canon Service (ETB, Netherlands).
The worksheet says for the body: Adjustment AF system * Adjustment Aperture/Shutter/Optical * Works according to specifications.
And for the 18-55IS: contacts cleaned * Works according to specifications.

After using the camera a few weeks it is clear that AF is much improved. When using center point focus it is now very good with all my lenses, huge difference! Kudos to Canon/ETB for the service. It now performs as well as my 300D (or maybe a tad better).

The bad news is that Multipoint AF is still not like it should be (consistent frontfocus with all lenses, check the last examples). And I still have the random severe FF issue (only in a few % of images, but still ...). With four 450D's showing the same AF problem out of the box, it must be a fairly common problem. NOT good, Canon needs to improve their quality control.

I purchased a Canon 450D camera in June 2008, but AF proved to be faulty in daily use - especially with the 18-55IS kit zoom, but also with some of my other lenses when used at longer distance (most of my DSLR work is 'landscape' photography; I don't shoot test cards for a hobby, and for macro I use a macro lens with manual focus so I didn't test AF at short distances). After lots of testing I decided to return the 450D kit. From the DPReview forums it is clear that many users are seeing the same kind of problems with the 450D (blurry, usually frontfocused shots with AF, while Liveview-MF or contrastAF gives excellent sharpness). I purchased a new kit to try again and decided to upload some images (most of all for all the naysayers who cannot imagine that Canon makes flawed products). The second 450D worked on average better than the previous kit, but still far from perfect.

FIRST ROW OF IMAGES: test summary for several lenses at 50-55mm focal length. First picture is the full image, scaled down 50%. Other pictures show unprocessed 100% crops from the test images, crop is from near center of image. Note that exposure is a bit unreliable (I used the standard evaluative metering for this test), so it varies a bit from picture to picture. Distance slightly adjusted because of 50/55mm focal length difference (Sigma EX is actually a bit less than 50mm). View all images at original size! I also ran this test to check image quality with the lenses that I had at 50-55mm; the 1.8/50II wins easily (especially in the corners, not shown).

SECOND ROW OF IMAGES: some other tests with the 450D and 18-55IS kit zoom. First picture shows the scene, other pictures are a series of 100% crops from near center of the image (where focus should be). Description of the test is usually at bottom of picture. View all examples at original size!

THIRD ROW OF IMAGES: tests with Sigma 2.8/18-50EX zoom. Again: first the whole scene, after that a series of 100% crops from middle of picture. It seems the AF problem occurs mostly with high contrast lighting (bright sunlight) but I'm not sure about that. With the Sigma center point AF is often worse than standard AF. Note: this Sigma EX zoom works fine on my 300D and AF was very good on the first 450D body.

FOURTH ROW OF IMAGES: various tests including images taken with my 2.8/200L II.

SECOND PAGE: fourth 450D body (I also tested one from a friend, same problem ...). This body was purchased to be used as an infrared camera, but I decided to test AF before IR conversion (it's not yet IR season anyway ...). First eight images as purchased, later images after adjustment at Canon service.

SUMMARY OF MY FINDINGS:

FIRST 450D KIT: very bad AF with 18-55IS at 18mm position (both standard and center-AF, always strong frontfocus) but very nice image quality when focused manual with Liveview. Very good AF with Sigma EX 2.8/18-50 (nearly spot on), unacceptable AF with Canon 1.8/50 II and 2.8/200 II (both seemed heavily front focused).

SECOND 450D KIT: pretty good AF with 18-55IS (when using center-AF, standard AF still not good), great image quality for the price with manual focus using Liveview. AF very good with Canon 1.8/50mm (except for standard AF), bad (and 'jumpy') with Sigma EX 2.8/18-50, bad with Canon 2.8/200L. I also found that manual focus using the focusing screen usually produces wrong focus, especially with the 2.8/200L.

FINAL VERDICT: nice camera with great image quality but unacceptable AF performance, second body is going back as well. No more 450D for me until Canon fixes the problem. I will keep using my 300D for now, and maybe choose a more expensive body later on (5D II?). If you want to leave constructive comments about my tests no problem, but pointless or rude remarks (like those that are common on dpreview) will be removed.