Pentax K-x Review: 28. Compared to (Resolution): Digital Photography Review

Resolution Chart Comparison (RAW)

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.

For a (more) level playing field we also convert our resolution tests using Adobe Camera RAW. Because Adobe Camera RAW applies different levels of sharpening to different cameras (this confirmed) we had to use the following workflow for these conversions:

Load RAW file into Adobe Camera RAW (Auto mode disabled)
Set Sharpness to 0 (all other settings default)
Open file to Photoshop
Apply a Unsharp mask: 80%, Radius 1.0, Threshold 0
Save as a TIFF (for cropping) and as a JPEG quality 11 for download

Please note that for this comparison we converted the E-620 RAW files in Capture One (using the default settings). This is because we have reason to believe that Adobe Camera Raw doesn't show the full resolution captured by recent Olympus SLRs (Capture One shows visibly more detail).

Pentax K-x (3.0 MB, 12.3 MP)	Canon EOS 500D (3.3 MB, 15.1 MP)


Nikon D5000 (2.6 MB; 12.3 MP)	Olympus E-620 (4.1 MB, 12.3 MP)

Pentax K-x	Canon EOS 500D


Nikon D5000	Olympus E-620

Pentax K-x	Canon EOS 500D


Nikon D5000	Olympus E-620

Pentax K-x	Canon EOS 500D


Nikon D5000	Olympus E-620

Measurable results

Camera	Measurement	Absolute resolution	Extinction resolution
Pentax K-x	Horizontal LPH	2350	* 2800
Pentax K-x	Vertical LPH	2400	* 3600
Canon EOS 500D	Horizontal LPH	2400	* 3300
Canon EOS 500D	Vertical LPH	2350	* 3200
Nikon D5000	Horizontal LPH	2400	3200
Nikon D5000	Vertical LPH	2350	3200
Olympus E-620	Horizontal LPH	2250	2650
Olympus E-620	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 resolution figures of all camera increase when shooting RAW but some gain more than others. Both the Nikon and Pentax improve significantly and in terms of absolute resolution almost catch up with the Canon EOS 500D. All cameras, apart form the Olympus E-620, show quite significant moire and artifacts, but this will almost certainly be a non-issue if you photograph scenes other than resolution charts.

< Previous | Next >