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.

Pentax K-7 (8.6 MB, 14.5 MP) Pentax K20D (8.5 MB; 14.5 MP)
Nikon D300 (3.3 MB; 12 MP) Canon EOS 50D (4.1 MB, 15.1 MP)

Pentax K-7 Pentax K20D
Nikon D300 Canon EOS 50D

Pentax K-7 Pentax K20D
Nikon D300 Canon EOS 50D

Pentax K-7 Pentax K20D
Nikon D300 Canon EOS 50D

Measurable results

Camera Measurement
Pentax K-7 Horizontal LPH 2300  * 2700 
Vertical LPH 2250  * 2650 
Pentax K20D Horizontal LPH 2250  * 2600 
Vertical LPH 2250  * 2500 
Nikon D300 Horizontal LPH 2200  2600 
Vertical LPH 2100  2600 
Canon EOS 50D Horizontal LPH 2250  2700 
Vertical LPH 2200  2700 

* 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 K-7 does quite well in this test. It makes the most out of its 14.6 MP sensor and produces a higher resolution than the 12 MP Nikon D300 and surprisingly also the EOS 50D, which comes with a higher nominal resolution. At very high frequencies there are some signs of moiré. When looking at these results though you have to consider though that they, like in all our studio tests, have been achieved with stopped down prime lenses. You won't get the same resolution out of the kit lens.