Photography is a process that must first understandable and sustained forever. Essence principles of photography as a transfer-recording only a projection of reality / object. That’s because we work with light factor. What is there (the object), there must be at the final result. And it’s no less or more. Nothing is removed or raised. Addition or subtraction of objects (which later became the subject) in the final result, not a photography. – Try to understand the tight – even had a very very tightly.
An optical lens, when compared with the optics of the eye (retina-pupil) – who knows how long will be equal it? An optical lens is a tool to resemble it. As far as what? Eyes that: Normal, it is impossible to make detailed / focused on one point only. Eye is unlikely to ‘blur / bokeh’ in the extreme foreground or background, such as lens 50 / 55mm in aperture diaphragm: f.1.2. So true is not it? Optical and photographic reference experts recommend optimization of the use of a 35mm lens on f.5.6. Why? Supposedly, it’s because the value of the corresponding synchronized showing almost universal leniency / flexible with the normal human eye. As far as what is tolerance? That is the challenge of adjustment. That’s the ‘Art’ in Photography, a reasonableness.