Unfortunately for those that like histrionic post processing effects '
Depth Of Field' is not in the least realistic in 2d flat projected of 3d games. In the real world, you can change your focus instantly from/to any object in your field of view, be it junk in your pockets, the front sight of the weapon, back to the rear aperture to make sure they're lined up, to any object in the world '
out there'.
'
Depth Of Field' as implemented in games locks you into a point of focus the game Developer decides is appropriate; i.e. he feels that aimed you should be focused on the target; where in fact even aimed and trying to make a shot Phoropter and Autorefractor measurements show a Shooter's eye is rapidly shifting focus from the front post to the target to the rear aperture -- though front post and target get the most attention.
Still worse, most '
Depth Of Field' post processing effects are ridiculously over done and not remotely to scale, blurring peripheral vision to 20:600 or worse which is patently asinine, putting the effect at four figure distortion of scale to reality. But what makes this effect totally absurd is the fact that there's already a mechanism of visual accommodation at work when we view flat projected 3d environment that works
to-scale the actual focus mechanics when seeing in the real world called
amplitude of accommodation.
Remember, we're looking at the flat projection of a 3d world in 2d, on a screen typically less then 24" (but the actual size doesn't matter, where the dimensions are anything less then half the real world and 2d), so all features of this world in order to be to-scale, need to be
smaller then real life; including even artificially forced DOF. The mechanics of amplitude accommodation accomplishes exactly this and can be demonstrated right on this forum page as you're reading this: look at one letter at the center of your screen, focus on it and do not shift your focus...
You'll notice letters peripheral to the letter you're focused on are increasingly out of focus, the farther they are from the letter you're focused on. In fact few people can even read the word adjacent to the word they're focused on without shifting their eyes. This error of visual accommodation has been carefully measured for simulator development and is almost exactly to-scale with actual DOF focus in the real world, more over it moves with your eyes and not as some canned game mechanic.
This '
Post Processing' effect, is just that; a special effect that has nothing to do with reality, borrowed from early film technique, adopted to 2d and later 3d digital filter effects -- it's as ridiculous as lens flairs on everything without a lense when they first appeared in games -- worse it's unrealistically narrowing an already limited FOV, which is narrower still where Aim-Zoom is implemented.