Resolution Chart Comparison

Shots here are of our 'version two' resolution chart which provides for measurement of resolution up to 4000 LPH (Lines Per Picture Height). A value of 20 equates to 2000 lines per picture height. For each camera the relevant prime lens was used. The chart is shot at a full range of apertures and the sharpest image selected. Studio light, cameras set to aperture priority (optimum aperture selected), image parameters default. Exposure compensation set to deliver approximately 80% luminance of white area.

Canon EOS 40D (2,646 KB, 10 MP) Nikon D200 (2,728 KB; 10 MP)
Pentax K10D (2,271 KB; 10 MP) Canon EOS 30D (2,409 KB; 8 MP)

Canon EOS 40D Nikon D200
Pentax K10D Canon EOS 30D (8 MP)

Canon EOS 40D Nikon D200
Pentax K10D Canon EOS 30D (8 MP)

Canon EOS 40D Nikon D200
Pentax K10D Canon EOS 30D (8 MP)

Measurable results

Camera Measurement
Canon EOS 40D Horizontal LPH 2100  2300 
Vertical LPH 1800  2300 
Nikon D200 Horizontal LPH 2100  2250 
Vertical LPH 1700  2200 
Pentax K10D Horizontal LPH * 2000  * 2300 
Vertical LPH 1800  * 2500 
Canon EOS 30D Horizontal LPH 1850  2100 
Vertical LPH 1650  2100 

* Moire is visible
+ Chart maximum
LPH Lines per Picture Height (to allow for different aspect ratios the measurement is the same for horizontal and vertical)
Absolute resolution Point at which all lines of a resolution bar are still visible and defined, beyond this resolution loss of detail occurs (below Nyquist frequency).
Extinction resolution Detail beyond camera's definition (becomes aliased)

The EOS 40D delivered exactly the same resolution as its smaller older ten megapixel sibling the EOS 400D, compared to the D200 there's not a huge amount of difference apart from noticeably less sharpening by default (as previously mentioned).