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 50D (4.1 MB, 15.1 MP) Nikon D300 (3.3 KB; 12 MP)
Pentax K20D (8.5 MB; 14.5 MP) Sony DSLR-A700 (2.6 MB, 12.2 MP)
 
Canon EOS 40D (2.6 MB, 10 MP)  

Canon EOS 50D Nikon D300
Pentax K20D Sony DSLR-A700
 
Canon EOS 40D  

Canon EOS 50D Nikon D300
Pentax K20D Sony DSLR-A700
 
Canon EOS 40D  

Canon EOS 50D Nikon D300
Pentax K20D Sony DSLR-A700
 
Canon EOS 40D  

Measurable results

Camera Measurement
Absolute
resolution
Extinction
resolution
Canon EOS 50D Horizontal LPH 2250  2700 
Vertical LPH 2200  2700 
Nikon D300 Horizontal LPH 2200  2600 
Vertical LPH 2100  2600 
Pentax K20D Horizontal LPH 2250  * 2300 
Vertical LPH 2250  * 2500 
Sony DSLR-A700 Horizontal LPH * 2200  2900 
Vertical LPH 2100  2800 
Canon EOS 40D Horizontal LPH 2100  2300 
Vertical LPH 1800  2300 

* 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)

As one would expect the EOS 50D delivers an increase of resolution over the 40D. Having said that compared to the 12 megapixel D300 and A700 the difference is surprisingly small.