First of all, it's not a distortion, it's reality, the result of an oblique projection. The human brain processes this back to the square angles it knows it consists of. To do the same with a picture is a architect nightmare, it requires either a special tilt-shift distorting lens like this
or special image processing software that can stretch and tilt images.
I assume that "50mm lens nearest human vision" is about standard lens focal distance, which is -by definition- equal to the largest diameter of the sensor. For the standard original SLR this would be the square root of 24^2 + 36^2 = 43.3 mm.
Most modern DSLR have smaller sensors so the standard lens focal distance would adapt accordingly. Crop factors are
2 for Olympus: Standard focal distance 22 mm
1.6 for Canon: Standard focal distance 27 mm
1.5 for most others including Nikon and Sony: Standard focal distance 29 mm