The 40D was to be a considerable upgrade from my 20D, or so I thought. A new model with a new sensor and most of the features missing from the 20D that everyone wanted. How could it not be better outright? Well it is and isn't.
I will cover the ergonomics, features and shooting performance first. This is where the 40D shines.
1. Liveview is useful for more than just astrophotography. I actually has a paying job within a week of getting the 40D where liveview made a difference. Event photography where one is forced to hold the camera overhead to get crowd shots is so much easier with this.
2. The 40D is faster to respond and get the shot from button press. It is much easier to get a bird in frame as it leaps from a branch. Blackout time between shots is much shorter allowing easier tracking of fast moving objects. 6.5 FPS is nice, but its advantage against 5 FPS of the 20D is not as significant as the response times and blackout times.
3. The viewfinder is brighter and larger.
4. Having your most used settings available in a quick access menu is very helpful when you need to change things on the fly during changing conditions.
5. Finally, ISO in the viewfinder and easily changeable on the fly!
6. I have rather large hands, so the larger grip and finger indent. is a nice comfort item for me over the 20D/30D.
7. A nice large LCD screen with RGB and luminance histograms is a very nice feature. What isn't so nice? The resolution of the LCD is a bit too low. The background of the histograms makes them hard to decipher in bright outdoor light.
8. The mirror moves faster as mentioned before for lower blackout times, but it is also a bit quieter. I have held on to my 300D for situations where camera noise would be intrusive and the 40D is almost quiet enough now for most sensitive situations.
9. Why oh why does Canon ignore all the cries about the wasted space on the camera for a direct print button? Why do they ignore the suggestion to make this button customizable?
10. Spot (semi) metering is a much welcomed addition over the 20D.
11. Highlight priority is quite useful for helping to keep that white bird from blowing out when you are not watching exposures as closely as you should be.
12. The biggest thing this camera does for a sports/wildlife photographer in my opinion is the large 17 image RAW buffer. It is very helpful when trying to get the best shot from an action sequence. I rarely bump into this limit.
14. It is very well built, but I wish it was fully weather sealed.
!5. The sensor cleaning seems effective. Where I had to clean my 20D senor regularly, the 40D has only needed a dust off a couple of times over the past few months for a couple of dust bugs that wouldn't go away on their own.
There are many other fine points about this camera that could be mentioned but they are in line with most of the other offerings in this level of gear.
Now for the contentious part as far as I am concerned, the image quality. There is nothing wrong with it, it's just that it culd have been better. Canon had to decide to increase the almighty megapixel count for marketing drones, or go for better image quality. Megapixels won.
Like I said, the image quality isn't bad. It's actually quite good and on par with the 20D/30D. I subjectively feel the IQ is a tiny bit less but I can't provide hard data to prove it, so lets say the 40D is as good as the 20D/30D. What the 40D has is more pixels, an approximate 12% increase. That's good if it means better images, but as I just said it doesn't mean that much.
What Canon should have done is applied the advances in sensor technology to the 8 megapixel sensor. Seeing as Canon had to drop the real sensitivity of the 40D 1/3 stop from the 20D, and added better lenses to get there, they could have applied the better lenses to the 20D sensor and gave us true 3200 ISO and maybe more. Lower light capability and faster shutter speeds wins over 12% more pixels in my opinion.
In closing, the 40D is a very capable camera that would meet the needs of most critical people. It isn't a 1D series performer, it's much better than any of the Rebel series for serious shooters, and its a good value. What I think it falls flat on is the sensor and it not being a real upgrade from the 20D/30D series. I don't look at my 40D images and go "Wow! These 40D images are better than my old 20D." Instead I find myself saying "Hmmm, nice features, but where are the better images?"
If you have a 20D, its most likely worth upgrading, but not for images quality. If you have a 30D, the only compelling reason I can see to upgrade is the sensor cleaning and liveview.