Resolution Chart Comparison (JPEG)

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.

Sony Alpha 550 (3.8MB, 14.2 MP) Canon EOS 500D (4.4MB, 15.1 MP)
Nikon D5000 (3.5 MB; 12.3 MP) Pentax K7 (8.6 MB, 14.5 MP)

Sony Alpha 550 Canon EOS 500D
Nikon D5000 Pentax K7

Sony Alpha 550 Canon EOS 500D
Nikon D5000 Pentax K7

Sony Alpha 550 Canon EOS 500D
Nikon D5000 Pentax K7

Measurable results

Camera Measurement
Sony Alpha 550 Horizontal LPH 2200 2500
Vertical LPH 2250 2550
Canon EOS 500D Horizontal LPH 2350  * 2550 
Vertical LPH 2300  * 2650 
Nikon D5000 Horizontal LPH 2200  * 2650 
Vertical LPH 2100  * 2600 
Pentax K7 Horizontal LPH 2300  * 2700 
Vertical LPH 2250  * 2650 

* Moiré 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 Alpha 550 is broadly comparable with the other cameras in its class when shooting JPEGs. There's very little moiré visible and the output is relatively clean, and doesn't look too over-sharpened.