We test the Canon 40D for image noise, both during short, daytime exposures and long, night exposures.
The Canon 40D is an excellent camera. It handles well, has an excellent control layout, has an excellent feature set and takes great shots.
Image quality is the topic of this test and specifically how noise changes by ISO sensitivity.
A 100% detail from the above, unsharpened or enhanced image:
So now lets have a look at image noise:
Noise is very well controlled through 800ISO. This is a very impressive performance.
To further explore this I shot test targets at typical daytime exposure times and also at a 15 second exposure time.
Short exposure noise:
As you can see shadow noise is there from 200ISO up but highlight noise only becomes quite noticeable at 1600ISO.
15 second exposure (note at 3200ISO we ran out of apertures, so it got a 1/2 stop extra exposure):
Again, noise is quite well controlled.
In this image we see the histogram from auto leveled 100ISO, 400ISO and 1600ISO greyscale test strips. In a camera with no noise at all the spikes should in theory be only one tone level wide. You can see here that they are pretty good at 100ISO but broaden quite noticeably as we move up the sensitivity levels.
As you can see by comparing the test target images with the real world ones, the camera actually shows less noise in real images than the test targets would suggest. The 40D is a great camera and is most impressive in use.