12-20-2016, 08:14 AM
Welcome on board 
There are two reasons why your assumptions will not lead to a valid result. First of all, a comparison across several test systems is an invalid approach in itself. It's tempting to 'normalize' the results, but bound to fail because so many factors influence a test system's maximum resolution, among those the sensor characteristics and the raw converter used in the analysis workflow. Short summary: the MTF results are not comparable across different systems (where every test camera we use is a 'system' in this context).
In addition, you're comparing apples and oranges anyway The AF-S 20/1.8 was tested on the D3x, so a full frame camera. The Tamron review is fairly dated and based on the D200, a DX camera with a smaller sensor. So border and corner values in those reviews refer to very different spots in the image circle of the lenses.
I can tell you, however, that the Nikkor does provide better sharpness (and way less CAs), and in addition opens up a few additional creative options with its fast f/1.8 aperture and the corresponding shallow depth of field. On the other hand, you lose the flexibility of the zoom.
Give me a little time, and I may be able to provide a few numbers so you can compare yourself
-- Markus
There are two reasons why your assumptions will not lead to a valid result. First of all, a comparison across several test systems is an invalid approach in itself. It's tempting to 'normalize' the results, but bound to fail because so many factors influence a test system's maximum resolution, among those the sensor characteristics and the raw converter used in the analysis workflow. Short summary: the MTF results are not comparable across different systems (where every test camera we use is a 'system' in this context).In addition, you're comparing apples and oranges anyway
The AF-S 20/1.8 was tested on the D3x, so a full frame camera. The Tamron review is fairly dated and based on the D200, a DX camera with a smaller sensor. So border and corner values in those reviews refer to very different spots in the image circle of the lenses.I can tell you, however, that the Nikkor does provide better sharpness (and way less CAs), and in addition opens up a few additional creative options with its fast f/1.8 aperture and the corresponding shallow depth of field. On the other hand, you lose the flexibility of the zoom.
Give me a little time, and I may be able to provide a few numbers so you can compare yourself
-- Markus
Editor
opticallimits.com
opticallimits.com