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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
Pentax K-7 (3.6 MB, 14.5 MP) Pentax K20D (3.5 MB; 14.5 MP)
Nikon D300 (2.8 MB; 12 MP) Canon EOS 50D (4.0 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
Absolute
resolution
Extinction
resolution
Pentax K-7 Horizontal LPH 2450  * 3150 
Vertical LPH 2400  * 3400 
Pentax K20D Horizontal LPH 2450  * 3100 
Vertical LPH 2400  * 3100 
Nikon D300 Horizontal LPH 2300  3200 
Vertical LPH 2250  3200 
Canon EOS 50D Horizontal LPH 2450  * 3300 
Vertical LPH 2350  * 3300 

* 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)

When shooting in RAW and using Adobe ACR to process the images the measured resolution increases on all four cameras. As in the JPEG comparison the K-7 produces very similar results to the K20D. It loses some of the advantage it had over the D300 in terms of JPEG resolution but nevertheless performs well and is pretty much on par with the 15.1 MP Canon EOS 50D.

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