Approximating the human eye

[selmerdave]

I read recently in a photography book that the human eye seems to perceive motion at roughly 1/15th of a second. Objects in motion will appear about as blurred in a photo taken at 1/15th of a second as they do to the naked eye. I don't know whether many people agree with this but it makes some sense to me.

I'm wondering if anyone knows of a similar equivalent for depth of field, or if anyone would like to guess one, say with a 50mm lens. f4?

Dave

 

[Unimaxium]

Well my assumption is that human eye DOF would change like the aperture on a camera, as our pupils / irises contract and expand depending on the amount of light. But I bet this would be hard for anyone to notice anyway since our brains do a good job of compensating.

 

[panchromatic]

The human eye stinks. Its our brains that do 90% of the "seeing", a good example of this is the blind spot test. Your brain takes most of the information and generates it. I always think of the human eye as a wide angle lens, and your DOF is quite small if focusing on something close and vise versa if looking at something far away... though your eye has very little edge to edge sharpness.


--Ryan

 

[lazarus219]

well i know if you put a pen about 5cm from your eye and look at it, your eye will focus on the pen and everything will blur except the pen, i guess that DOF. I have been wondering about the eye since i got into photography- because i know video cameras still use the shutter to make each frame but i just figured your eyes are always open right? (like a shutter not open like it usually means)

 

[Hertz van Rental]

The problem is that we do not perceive everything the eye sees - and the eye is by no means very well designed - so any discussion on what the eye sees has to take the brain (and indeed psychology) into account.
The information gathered by the eye is processed - and processing starts in the optic nerve (by the way it is constructed). The brain then filters and interprets this information and fills in any gaps - and also leaves out a lot.
The shortest interval the brain can comprehend is 1/60th of a second but the eye can capture much shorter intervals. A flashgun going off can generate a light for less than 1/10,000th of a second. The eye catches this but the brain interprets it as 1/60th.
The hardest thing to get to grips with is that colour, as we perceive it, does not exist outside the visual cortex.
As for depth of field - this is affected by lots of factors in the eye. The lens changes shape, the pupil aperture varies, even the shape of the eyeball changes. The eye is doing all this constantly. And then, of course, the brain is involved. Not to mention the zones on the eye - the central area and the peripheral zone. Oh, and the blind spot where the optic nerve leaves the eye.... and the fact that light has to travel through a several layers of cells before it hits the rods and cones... and the capillaries that are in front of the light receptors...
If anyone tries to argue in favour of 'intelligent design' as opposed to Darwin, just show them the human eye and mutter about 'bl**dy amateurs'. ;-)

 

[Rob]

there is no I in team.

There may be no I in team, but there is a U in c%nt.

Sorry, couldn't resist.

 

[panchromatic]

Man is that what you believe, So another wards you will go out and buy the most expensive camera and put the cheapest lens you can find on it. Does that even make sense. The eye and the brain work as one, there is no I in team. there is no camera that can match the human eye and brain both are marvels that can not be reproduced. I am not trying to be a prick or anything and everyone is entitled to thier opinion, but that statement was so WRONG

i was not comparing anything to do with cameras, that is a total apples and oranges comparison. The camera does not plug in spots that are missing or covered (like the brain does.) You have blind spots, nerves and other things covering what you "see" and the brain "removes" them and replaces them with what it things should be there (BLIND SPOT). Cameras record what is there, if you have massive finger prints on your lens then your camera sees it. I never said the brain and eye do not work as one, in fact I said they do. I never said a camera was better than the human eye and brain, if my camera had a brain then it would be the best thing ever.

next time read what i am saying before you post, and if you post do not put words in my mouth i do not appreciate it.

and you definitly where trying to be a prick.

 

[thebeginning]

Sorry that comment reminded me of a lil joke and I thought it would be good for this.

Who's the Boss?



When the body was first made, all the parts wanted to be boss. The brain said, "Since I control everything and do all the thinking, I should be boss." The feet said, "Since I carry the body around to where it wants to go, and get into position to do what the brain wants, I should be boss." The hands said, "Since I do all the work and earn all the money to keep the rest of you going, I should be boss."

And so it went with the heart, the lungs, and the eyes. And finally, the asshole spoke up and demanded that it be made boss. All the other parts just laughed and laughed at the idea of an asshole being boss.

The asshole was so angered that it blocked itself off and refused to function. Soon the brain was feverish; the eyes crossed and ached; the feet were too weak to walk; the hands hung limply at the sides; the heart and lungs struggled to keep going.

All pleaded with the brain to relent and let the asshole be boss. And so it happened. All the other parts did all the work, and the asshole just bossed around and just pass all the **** to the rest. THE MORAL OF THE STORY: You don't have to be a brain to be boss, just an asshole.

this has been the only worthwile post in this entire thread. :-D

ive never noticed my eye's (or brain, whatever) DoF...it's very hard to tell. but i think i do agree with the 1/15 thing. it seems so much faster, but once you think about it, it does make sense. your eyes just tend to follow things i guess, so it compensates for the blur.

 

[DocFrankenstein]

Don't anybody know physics here?

To get the same bokeh in camera as the "human eye"
Diameter of the pupil = diameter of the diaphragm

Problem solved

 

[selmerdave]

Isn't it a factor of the relative relationship rather than the absolute size? I think in room lighting my pupil would be a similar size to the aperature of a 50mm lens at f22. A photo at that opening, even of a close object would have considerably more depth of field than I perceive that I have.

Dave

 

[DocFrankenstein]

My eye in a relatively bright room has a diameter of 4mm (just checked in the mirror)

50/x=4
x~12

50mm f/12

or...

35mm at f/8

or...

24 at f/5.6

 

[jadin]

Television is roughly 30 frames per second, or 1/30th of a second per frame. Anything lower and video won't be fluid. Video games also try to maintain at least 30 fps, ideal 60 fps. IMO the eye needs at least 30 fps, but is probably closer to 60.

Also, Hertz, I don't think you give the eye enough credit, for starters how fast an eye focuses. It's so fast it doesn't need a large DoF, no matter what you look at it's in focus. Also it serves our purposes. Take a bird of prey's eye, it can see miles away things as small as a mouse roaming a field. Human's don't need to hunt like that, so our eyes aren't as keen. It was designed with what we needed to see... (cut short due to time)

 

[Hertz van Rental]

Television is roughly 30 frames per second, or 1/30th of a second per frame. Anything lower and video won't be fluid. Video games also try to maintain at least 30 fps, ideal 60 fps. IMO the eye needs at least 30 fps, but is probably closer to 60.

Also, Hertz, I don't think you give the eye enough credit, for starters how fast an eye focuses. It's so fast it doesn't need a large DoF, no matter what you look at it's in focus. Also it serves our purposes. Take a bird of prey's eye, it can see miles away things as small as a mouse roaming a field. Human's don't need to hunt like that, so our eyes aren't as keen. It was designed with what we needed to see... (cut short due to time)

Oh I know exactly what the human eye can do. I've even disected a few. I was just making the point that it has it's faults and it is folly to try to compare it to a camera.
There has also been some recent research into just how fast an eye can focus. It's not as quick as you think.
The effective aperture is varying constantly and is not really conected to depth of field so you shouldn't try to compare it.
The brain does an awful lot of 'fudging' - that is, smoothing out the defects.
For example, your ability to percieve colour changes over time. At 6 you see colours with up to three times the intensity that you do at 60. But you are not aware of it because the brain compensates.
The same goes for focusing.
You need to see the brain as being a bit like Photoshop doing post production on the image.

Only SMPTE video frame rate is 30fps. EBU (European PAL) is 25fps. It's to do with mains frequency (60Hz and 50Hz respectively). Apparent motion is just as smooth.
And I do believe that I said that the shortest time span the brain could differentiate was 1/60th sec.

 

[DocFrankenstein]

Hertz - why does the effective aperture of eye isn't really connected to DOF? Please clarify.

 

[Hertz van Rental]

The eye shifts focus as you look at things and you only focus on a relatively small area so depth of field does not really come into play.
If you try to 'see' the depth of field, your eye just refocuses which defeats the whole thing.
It's not that the eye doesn't have a depth of field it's just that the way we see doesn't have much need of it or provide any way of utilising it.
The pupil is to do with controlling illumination levels but it's size is also affected by our physical and emotional state.
To give you an example - if you look at something you like or someone you find attractive your pupils get bigger. If the eye used depth of field then this would reduce it which, in this situation, would be counter-productive.
Think how annoying and confusing it would be if how much of something was in focus kept constantly changing as your pupil dilated or contracted.
You really must try not to see the eye as working like a camera lens. There is no comparison.