[arvydas]

Well, while lenses do have limited DOF, only photography really has made an art out of it to isolate subjects, so to speak, i.e. the large sensors and lens physics (aperture) automatically forced photographers to work with that. Camera obscuras (pinhole) of the old school painters didn't have that limitation, so you don't see any out of focus blur in their paintings ;-)  

And the human eye really is mostly looking at the world all sharp, because it focuses constantly on what we are looking at, and it has a pretty good DOF. Most of depth perception comes from our 3D view and knowledge of our surroundings, not from blur. But blur can replace that to some degree in 2D images.

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.