# Approximating the human eye



## selmerdave (Mar 9, 2005)

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 (Mar 9, 2005)

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 (Mar 9, 2005)

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 (Mar 9, 2005)

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 (Mar 10, 2005)

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 (Mar 10, 2005)

bp22hot said:
			
		

> 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 (Mar 10, 2005)

bp22hot said:
			
		

> 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 (Mar 10, 2005)

bp22hot said:
			
		

> Sorry that comment reminded me of a lil joke and I thought it would be good for this.
> 
> *Who's the Boss?*
> 
> ...



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 (Mar 10, 2005)

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 (Mar 10, 2005)

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 (Mar 10, 2005)

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 (Mar 12, 2005)

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 (Mar 12, 2005)

jadin said:
			
		

> 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 (Mar 12, 2005)

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


----------



## Hertz van Rental (Mar 12, 2005)

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.


----------



## DocFrankenstein (Mar 12, 2005)

In that case, you might say that the eye + brain have no DOF at all, which I agree with.

BUT: when you're looking at the print the DOF matters imo, and that's where the DOF of the eye should match the dof of the eye...

I'm curious. Why would anybody want to approximate the human eye? What do u think that will accomplish?


----------



## walter23 (Mar 12, 2005)

bp22hot said:
			
		

> 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



The eye is good but it really is the brain that does most of your seeing.  When you look at a scene you are constantly scanning it and focusing on different points while your brain assembles this information into a panorama with basically infinite depth of field.  So I guess the best answer to the camera-analogue question would be ultra-wide with infinite depth of field.


----------



## lampuiho (Jan 6, 2013)

Most of you must have failed high school biology because the pupil only changes the amount of light going into your eye. It does not change the DOF. It is that the lens that change the magnification. And they are controlled by the ciliary muscle. By changing the magnification, the distance to perfect focus change but the depth of field doesn't change at all.


----------



## Helen B (Jan 6, 2013)

lampuiho said:


> Most of you must have failed high school biology because the pupil only changes the amount of light going into your eye. It does not change the DOF. It is that the lens that change the magnification. And they are controlled by the ciliary muscle. By changing the magnification, the distance to perfect focus change but the depth of field doesn't change at all.



You don't really understand optics, do you?


----------



## rexbobcat (Jan 6, 2013)

lampuiho said:


> Most of you must have failed high school biology because the pupil only changes the amount of light going into your eye. It does not change the DOF. It is that the lens that change the magnification. And they are controlled by the ciliary muscle. By changing the magnification, the distance to perfect focus change but the depth of field doesn't change at all.



Totally, because it's not like the pupil is ANYTHING like the aperture of a camera lens.


----------



## Buckster (Jan 6, 2013)

Helen B said:


> lampuiho said:
> 
> 
> > Most of you must have failed high school biology because the pupil only changes the amount of light going into your eye. It does not change the DOF. It is that the lens that change the magnification. And they are controlled by the ciliary muscle. By changing the magnification, the distance to perfect focus change but the depth of field doesn't change at all.
> ...


He also doesn't understand what it means to dig up threads that have been dead for nearly 8 years and try to take a crap on its participants.


----------



## Buckster (Jan 6, 2013)

Hertz van Rental said:


> 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.


I don't think it would be counter-productive at all.  When the pupil/aperture widens, foreground and background elements blur more, allowing us to have the actual subject more isolated.  This makes sense to me in the case of looking at someone we find attractive.


----------



## lampuiho (Jan 6, 2013)

Buckster said:


> Helen B said:
> 
> 
> > lampuiho said:
> ...



It's funny you said that when it's not called taking a crap on the participants. This is more like clearing up misconception.

A discussion of nature can never be dead. Information is still relevant even if it's 8 year old.

Changing the size of the pupil doesn't change the size of the lens or focal length or magnification at all. But it does change the angle the light can go in. But it is largely irrelevant because it still doesn't change whether light gets focused on your retina.

Do you really think you can see further by making your hand scope like and put it in front of your eye? Definitely not, I tried.

I would accept your point if you have any sort of proof. But varying pupil sizes just don't change the depth of field for me.


----------



## amolitor (Jan 6, 2013)

Optical depth of field is almost a meaningless concept for eyes. It's there, I guess, but largely irrelevant. The imaging system is only a very tiny part of how the image we "see" is constructed.


----------



## lampuiho (Jan 6, 2013)

amolitor said:


> Optical depth of field is almost a meaningless concept for eyes. It's there, I guess, but largely irrelevant. The imaging system is only a very tiny part of how the image we "see" is constructed.



It's meaningful because I've recently been working on a depth of field post-processing shader program.


----------



## KmH (Jan 6, 2013)

Well good luck to you with that.

Will the DoF post-processing shader program work like the human eye?


----------



## Buckster (Jan 6, 2013)

lampuiho said:


> Buckster said:
> 
> 
> > Helen B said:
> ...


*THIS IS* trying to take a crap on the participants, and was uncalled for: "_Most of you must have failed high school biology"_



lampuiho said:


> This is more like clearing up misconception.


Except that you're not.



lampuiho said:


> A discussion of nature can never be dead. Information is still relevant even if it's 8 year old.


Common forum etiquette is in play here.  An 8 year old thread's participants are usually long gone, and the thread is DEAD.  If you want to have this discussion with the current forum participants, start a new thread and deliver your message.



lampuiho said:


> Changing the size of the pupil doesn't change the size of the lens or focal length or magnification at all.


Nobody said it does, so you're just constructing a strawman with that statement.



lampuiho said:


> Do you really think you can see further by making your hand scope like and put it in front of your eye? Definitely not, I tried.


Again, that's not what ANYBODY is saying.  You don't actually know what DOF is, do you?



lampuiho said:


> I would accept your point if you have any sort of proof. But varying pupil sizes just don't change the depth of field for me.


The pupil dilating has to change the DOF - it's simple optical physics, like it or not.  It doesn't mean it gives you telescopic eyes (the argument you seem to be trying to strawman against), it means that DOF changes.

The human eye changing focal length by looking at something very close up vs. something very far away does it as well, just like a camera's lens does.  When looking at something inches from our face, the DOF is very narrow, compared to looking at mountains far off in the distance, where the DOF is miles deep, not a few inches.


----------



## Buckster (Jan 6, 2013)

By the way, here's an experiment you can try that I learned as a kid who needed glasses at age 10: Put a pinhole in a piece of paper, then look through it - the whole world gets sharper.  Guess why?  Smaller aperture at the front of the eye causes a change in DOF, increasing it significantly.


----------



## Josh66 (Jan 6, 2013)

There was an interesting discussion about this in the 'I Shoot Film' group on Flickr a few weeks ago - Flickr: Discussing apertures vs eye balls in I Shoot Film


----------



## kundalini (Jan 6, 2013)

[off topic]



O|||||||O said:


> There was an interesting discussion about this in the 'I Shoot Film' group on Flickr a few weeks ago - Flickr: Discussing apertures vs eye balls in I Shoot Film


Dude, I haven't seen you post in ages.  Hope you had a good holidays.

[/off topic]


----------



## lampuiho (Jan 6, 2013)

DOF is the distance to the perfect focus that still remain clear.

From what I see, whether things still stay in focus has to do with whether the light that goes to the retina converge or appear to be converged (scattered but the scattered light is not sensed by another cell).

Yes, the size of your pupil can change the blur radius because of how much wider the light can go in and scatter to more area. 

But I don't see how it makes more things stay in focus since light still get scattered no matter the size of  your pupil.


----------



## lampuiho (Jan 6, 2013)

Buckster said:


> lampuiho said:
> 
> 
> > Buckster said:
> ...


----------



## Buckster (Jan 6, 2013)

lampuiho said:


> DOF is the distance to the perfect focus that still remain clear.
> 
> From what I see, whether things still stay in focus has to do with whether the light that goes to the retina converge or appear to be converged (scattered but the scattered light is not sensed by another cell).
> 
> ...


Your misinformed opinion is just that, and largely incorrect because you have some ideas about what DOF is that are not supported by the science of optical physics.

Eyes and camera lenses have essentially the same physical characteristics and mechanical parts, and therefore work essentially in the same way.  The lens is the lens in both.  In the eye, the pupil acts as the camera lens aperture blades, both getting smaller to let in less light so we don't "overexpose" and be blinded and, like it or not, the physics of the diameter demand a difference in DOF in both eyes and camera lenses - it's physics - it doesn't change just because you can't seem to see it or figure it out any more than any other laws of physics.  The eye's retina acts as the camera's sensor or film, where the lens and aperture blades/pupil focus the image.

Again, look at something close up and something far away.  Note the difference in DOF (go read about DOF too, btw, because you still haven't got that straight).  Do the pinhole experiment and note the difference in DOF between that surrogate pupil in front of your eye and your actual pupil, which will be much wider.

You're like a guy who's barged into a physics forum and is telling a group of amateur AND working physicists that there's no gravity on Mars because YOU haven't personally detected it and therefore can't seem to wrap your brain around it.


----------



## Buckster (Jan 6, 2013)

lampuiho said:


> Buckster said:
> 
> 
> > lampuiho said:
> ...


How is it obvious to you that the participants failed high school biology?  Oh, that's right, you've already demonstrated that you jump to conclusions that are not supported by scientific data or hard facts.

Chances are that every one of them that took high school biology passed, but feel free to present the ACTUAL EVIDENCE that they failed.

Oh, that's right...  You don't _*HAVE*_ any _*ACTUAL*_ evidence to support your ad hom, do you?  Awwww...  Too bad...


----------



## KmH (Jan 6, 2013)

File - Depth of field illustration.svg - Wikipedia, the free encyclopedia

When the pupil of an eye changes size, the focal ratio (f-number) of the eye changes.

Have you looked at this? - Entrance pupil - Wikipedia, the free encyclopedia


----------



## Helen B (Jan 6, 2013)

lampuiho said:


> DOF is the distance to the perfect focus that still remain clear.
> 
> From what I see, whether things still stay in focus has to do with whether the light that goes to the retina converge or appear to be converged (scattered but the scattered light is not sensed by another cell).
> 
> ...



DoF is not about what is in focus. You are correct that the size of the iris does not affect the point of focus (aberrations aside) but you appear to fail to understand that it is not relevant. DoF is about apparent focus, not actual focus, and the size of the iris does affect that. You also appear to misunderstand why things are out of focus - it is not scattering. You should try to learn some basic optics.

Apart from the optical theory, those of us with myopia can see it in practice. Without glasses, I can get aparrent focus further away in bright light than in dim light, and if you try using an artificial aperture immediately in front of your eye you can see more in focus.


----------



## Buckster (Jan 6, 2013)

Helen B said:


> Apart from the optical theory, those of us with myopia can see it in practice. Without glasses, I can get aparrent focus further away in bright light than in dim light, and if you try using an artificial aperture immediately in front of your eye you can see more in focus.


EXACTLY what I learned at 10 years old, and the pinhole experiment.


----------



## Helen B (Jan 6, 2013)

Buckster said:


> Helen B said:
> 
> 
> > Apart from the optical theory, those of us with myopia can see it in practice. Without glasses, I can get aparrent focus further away in bright light than in dim light, and if you try using an artificial aperture immediately in front of your eye you can see more in focus.
> ...



And that is why we squint to improve focus when we aren't wearing glasses - the eyelids act as secondary pupils.


----------



## deeky (Jan 7, 2013)

I think the problem (aside from dredging a rediculously old post) with finding the evidence is that in a captured photo, the image and dof is frozen, so we can move the selective focus of our eye around the photo to study the portions that are oof.  When studying the oof portions of our sight, as soon as you try to look at the oof portions, your point of focus changes and that portion you are now trying to look at automatically comes into focus, making it appear that all portions are in focus.  Silly brain - trying to focus on the center of our attention.

When I try to picture a study of dof in your own eyesight, I get the image of a dog chasing its own tail, just with your eyes (or someone on a bad acid trip watching the pink elephants fly around the room).  

_(Yes, portions of this is meant to be a bit synical.)   _


----------



## Helen B (Jan 7, 2013)

I think that point was already covered in the thread, to be fair to the original participants. It's why those of us with myopia are more aware of DoF, I think: we can't focus distant things so we need ways of increasing our DoF if we aren't wearing corrective lenses to reduce our eye's power.


----------

