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

Canon EOS 7D (4.7MB, 18 MP)	Canon EOS 50D (4.0 MB, 15.1 MP)
Nikon D300s (3.2 MB, 12 MP)	Pentax K7 (3.6 MB, 14.5 MP)

Canon EOS 7D	Canon EOS 50D
Nikon D300s	Pentax K7

Canon EOS 7D	Canon EOS 50D
Nikon D300s	Pentax K7

Canon EOS 7D	Canon EOS 50D
Nikon D300s	Pentax K7

Measurable results

Shooting in RAW and using Adobe ACR to process the images increases the measured resolution on all four cameras but the difference is less obvious on the 7D than on the competitors. Nevertheless, while the absolute resolution remains almost unchanged, extinction resolution is increased which improves the rendering of very fine detail in an image.