We analysis the lens systems with MTF , Color MTF , different seidel or zernike abberations.

Some Leica lenses are interesting , for example Summicron 50. When you look to the MTF Chart , you find there are 2 images in one image. One is contrasty and other is less sharp. This goes in to classify the lines of the image , if there is a center of the image ,some lines represents tangential , others are parallel to the virtual rays spreading from the image center.

At Leica , whenever the one class sharpens , other class blurs and the opposite .

And the blur is calculated so well , it gives a healthy , lively , smooth , a holographic pop up detailed skin.

Well , I defend , this is similar to classic paintings.

They are built from many layers , deep layer blurred , top layer sharp and everything transparent.

Well , can we define , analysis these paintings with analogy of indicated tests. May be yes , but may be there are other analysis , synthesis techniques.

So what do you know ?