DxOMark have come up with a new way to measure the sharpness of lenses.
DxOMark say the new Perceptual Megapixel: "provides photographers with a means of instantly understanding the performance of a lens by quantifying its impact on the perceived resolution of the camera with which it is coupled."
Designed by DxOMark experts, Perceptual Megapixel quantifies the sharpness “perceived” by the photographer while taking into account all the characteristics and defects of the lens and the camera.
Frédéric Guichard, Chief Scientific Officer for DxO Labs says: "This new unit of measure replaces the MTF scores that we have been publishing up until now. Perceptual Mpix weights MTF measurements with the sensitivity to detail of the human visual system, thus providing a score for the sharpness perceived by our eyes. We think this new measurement will be more understandable and practical for photographers who use our website."
The Perceptual Megapixel measurement allows for making numerous comparisons among cameras and for the first time quantifies the impact of lens sharpness on camera resolution. Thus the perceived resolution for a camera can be significantly different from the native resolution depending on the lenses with which it is coupled.
For example, when coupled with a Canon EOS 5D Mark II
camera with a 21.1 Mpix sensor, a Sigma 35mm f/1.4 DG HSM lens has a Perceptual Mpix score of 17.2, whereas a lens such as the Carl Zeiss Distagon T* 35mm f/1.4 ZE has a Perceptual Mpix score of 15.2.
The example above is based on data from DxOMark’s database of test reults for more than 2,700 camera and lens combinations. These tests reveal that, on average, about 45% of the resolution is lost due to lens defects.
This new metric introduced by DxOMark aligns with the standardization work currently being undertaken by the IEEE, the International Imaging Industry Association (I3A), and the ISO — and in which DxO Labs actively participates. Perceptual Mpix is also based on the scientific findings of CNES (the French space agency) pertaining to the optimization of digital acquisition, notably in the field of satellite imagery.
Visit DxOMark's website