[Guest]

In fact, blur was important part of paintings since renaissance; for example sfumato style was introduced by Da Vinci, and Dutch "tonal phase" landscapes are full of blur to make an atmospheric depth effect; blurry paintings by J.M.W. Turner; and more recent famous blur by Gerhard Richter. Some like it, others don't, but blur is here for centuries .

The real human depth perception, arising from disparate objects projections at both eyes, is possible only when subject is 3D; otherwise 3D effect is created by monocular cues, like perspective, paralax etc., and out of focus blur is just one of these cues. IMO human eye would get only one star rating here, at PZ. Sharp is only centre, and then visual acuity rapidly falls down going to periphery. Similarly with DOF - it depends on distance and accommodation, but it is far from perfect. It's just our brain make us think that we are so good.

 

A.

 

Yes, of course blur is in paintings, but it's mostly not used like in a mathematical DOF function of a lens. You will notice that the background in Da Vinci's Mona lisa is not a blur, but a recreation of haze etc.   And Turner had apparently an eye disorder in his later days. 

 

As pointed out, yes, the eye does focus, and if you get old, you can't adjust anymore. But that last example really makes it clear how much we are used to seeing sharp, because we really only see with the very center. The unsharp parts in the periphery contribute to our motion detection senses, so we turn our attention to something that attacks us. We don't see our total surroundings in one go, we have to assemble it from the center part by scanning, and the brain assembles the sharp parts. What perhaps does go into distance analysis is how the eye has to accommodate to different distances, which may trigger some distance feedback cue, although I am not sure if the latter exists, or if everything is done just by 3D vision.

Anyway, my point is that there is not conscientious visible DOF in our vision, like one sees in a picture taken with a 50mm f1.4 lens.