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Author Topic: Angle of view of the human eye when fixed upon an object.  (Read 7093 times)
David S
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« on: June 14, 2012, 08:52:17 AM »
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Many years ago, a popular photography magazine ( I believe it was Modern Photography) did an article looking at the camera lens needed to duplicate the angles of view of various scenes in classic oil paintings. I am looking for references to that article or any other references that discuss this issue.

I know the eye has been said to have various "angles of view" depending on how we make the measurement from about 150 degrees on down. But if the eye is focused on an object the angle of view is said to be much less and this is the issue I am looking for more information on.

Any references would be appreciated.

Dave S

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JohnTodd
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« Reply #1 on: June 14, 2012, 10:53:26 AM »
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David,

Are you talking about the phenomenon that *if the eye doesn't move*, it is shown to only resolve sharply over a very small area (about two degrees, IIRC)? As we know, the eye constantly moves subconsciously, picking up detail all over the field of vision. I've heard of a demonstration where an observer's eye muscles are temporarily paralysed, revealing how little of the field of view is actually resolved; apparently, it's immensely disturbing.
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langier
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« Reply #2 on: June 14, 2012, 11:07:07 AM »
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Our fovea centralis ain't too large and our eyes seem to work like some of the high-res capture devices with steppers, but on lots of steroids! Best (and worse of all), it's attached to a "brain" that makes all those sensors seem quite rudimentary in comparison! 
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David S
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« Reply #3 on: June 14, 2012, 11:11:45 AM »
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Our fovea centralis ain't too large and our eyes seem to work like some of the high-res capture devices with steppers, but on lots of steroids! Best (and worse of all), it's attached to a "brain" that makes all those sensors seem quite rudimentary in comparison! 

I am trying to find out more about how artists from earlier centuries (say 1600-1900) represented what they saw and put to canvas their ideas so I might do the same with a camera and lens including the same "angle of view" they used. (Is that clear?)

Dave S
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shadowblade
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« Reply #4 on: June 14, 2012, 12:05:24 PM »
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I am trying to find out more about how artists from earlier centuries (say 1600-1900) represented what they saw and put to canvas their ideas so I might do the same with a camera and lens including the same "angle of view" they used. (Is that clear?)

Dave S

Look up 'camera obscura' on Google or Wikipedia.
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Ray
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« Reply #5 on: June 14, 2012, 12:35:27 PM »
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This is an interesting issue which is also quite puzzling to me. I recall there being a general opinion that a standard lens (45 or 50mm for the 35mm format) is close to what the eyes see, but this seems to be only true with respect to magnification, and even then not quite true. A  60mm or 70mm lens seems to produce a closer match, regarding magnification, with 35mm format.

Hovever, the eyes have a very wide peripheral vision which includes objects which are only vaguely discerned, without detail. Such a wide field of view would approximate the FoV of a 12mm rectilinear lens, in 35mm-format terms, except that the 12mm lens would more clearly define the outer objects in the wide scene, and any object in the centre of the scene, viewed through the viewfinder with 12mm lens attached, would look very small, compared with what the eyes sees in reality, away from the viewfinder.

I believe there is a problem in the sense that no camera lens can duplicate what the eyes see in reality, in terms of these three factors of (1) magnification, (2) field of focus, (3) general angle of view including out-of-focus areas.

The eye appears to have a 'focussed angle of view' as narrow as a long telephoto lens, the magnification of a standard lens or slightly longer, and the general angle of view, including peripheral vision which is OoF vision, of that of a 12mm lens at an impossible aperture of F0.5, or something similar.
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Ellis Vener
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« Reply #6 on: June 14, 2012, 05:56:00 PM »
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I am trying to find out more about how artists from earlier centuries (say 1600-1900) represented what they saw and put to canvas their ideas so I might do the same with a camera and lens including the same "angle of view" they used. (Is that clear?)

Well primarily they used their minds and their imagination and decided what to put in and what to leave out. I would not take any artist's work as a  literal interpretation of reality no matter how realistic it appears to be - and that goes for photography as well.  There is the art of composition which includes framing, and the arts of manipulating lighting effects and color to create a sense of depth and to lead a viewer's eye to what the artist wants you to pay attention too. It was not until quite recently that photographers had the range of tools available to them that painters have had for centuries if not millennia.
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BartvanderWolf
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« Reply #7 on: June 14, 2012, 06:19:41 PM »
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I am trying to find out more about how artists from earlier centuries (say 1600-1900) represented what they saw and put to canvas their ideas so I might do the same with a camera and lens including the same "angle of view" they used. (Is that clear?)

Hi David,

Yes, it is clear, and it doesn't make sense at the same time, because using a lens and a projected output size will introduce anamorphic projection distortion when viewed from different distances/positions.

Since the Renaissance period, artists were very much aware of the concept of projection distortion, but they mostly painted from their personal 'perspective' (viewpoint), and because they did not use lenses and different output formats the image was not viewed from vastly different distances.

This has also been discussed (at nauseam one might add) in a LuLa thread called "Perspective Revisited". Let's not repeat all that. Your question is  a valid one, but it cannot be answered without some basic understanding of what we're dealing with. Angle of view is not only what it is about, so that by itself cannot lead to a meaningful answer. Differences in viewing (projection) distance and angle is the key.

Cheers,
Bart
« Last Edit: June 15, 2012, 02:47:56 AM by BartvanderWolf » Logged
Petrus
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« Reply #8 on: June 14, 2012, 11:30:52 PM »
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I've heard of a demonstration where an observer's eye muscles are temporarily paralysed, revealing how little of the field of view is actually resolved; apparently, it's immensely disturbing.

Actually, if the eye muscles are paralyzed and the eye stops moving it will also stop seeing. The reason: there has to be constant change of illumination on the rods and cones as they can detect only change, not steady state. For that reason the eyes always move just slightly, something we can not prevent no matter how hard we try.
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Ray
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« Reply #9 on: June 15, 2012, 08:59:04 PM »
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Actually, if the eye muscles are paralyzed and the eye stops moving it will also stop seeing. The reason: there has to be constant change of illumination on the rods and cones as they can detect only change, not steady state. For that reason the eyes always move just slightly, something we can not prevent no matter how hard we try.

It's called saccadic eye movement. For those who are deeply into technical matters, the following two links should give you a fair idea of the issue, but I can't see how this is relevant to photography.

Even when you attempt to focus on something continuously, with a fixed stare, your eyes are moving very slightly all the time, but so quickly you are not aware of it. You have no control over such rapid movements, so forget about it.

http://en.wikipedia.org/wiki/Saccade

http://www.psychology.uiowa.edu/faculty/hollingworth/prosem/Hoffman_Subramaniam_95_PP_RoleOfVisual.pdf
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Ray
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« Reply #10 on: June 15, 2012, 09:07:34 PM »
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This has also been discussed (at nauseam one might add) in a LuLa thread called "Perspective Revisited". Let's not repeat all that. Your question is  a valid one, but it cannot be answered without some basic understanding of what we're dealing with. Angle of view is not only what it is about, so that by itself cannot lead to a meaningful answer. Differences in viewing (projection) distance and angle is the key.

Cheers,
Bart

Bart, what good news! We don't have to revisit the problem of anamorphic distortion You've got a solution that we can all use, so that it's no longer a problem? Please advise all of us what that solution is.  Grin

Regards,  Ray
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BartvanderWolf
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« Reply #11 on: June 16, 2012, 09:51:45 AM »
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Bart, what good news! We don't have to revisit the problem of anamorphic distortion You've got a solution that we can all use, so that it's no longer a problem? Please advise all of us what that solution is.  Grin

Hi Ray,

The OP thinks there might be a link between the vision of the old masters to a Field of View of a lens.

Watch the following clip, and answer the following question: Does the photographer look through his viewfinder to decide which lens is needed, or does he position himself/his camera in such a position that the perspective is right?
http://www.youtube.com/watch?v=NTG8UCUeZxw

Just like the original painter Johannes Vermeer, Erwin Olaf poses the model in an arranged setting and he records him/her while viewing from a given position. The choice of lens (focal length) will only determine the crop of the scene for the sensor size in his camera.

In Vermeer's time, there were hardly any lenses used for imaging, although there are suggestions that he was familiar with the concept of a Camera Obsura. Look at this clip, which at 1:43 even stresses that the perspective is a perfect reconstruction of viewing the scene from a specific vantage point which helps to focus on a specific vanishing point, the focus of attention. Only a carefully chosen viewpoint in relation to the subject and direction of view play a role, and can achieve that. No lenses, mirrors nor smoke were required.

Here are some more examples of the use of perspective, deliberate distortons, alteration of shadows, simultaneous color contrast (Vermeer would have loved Photoshop if he were a contemporary photographer, no doubt):
http://www.artbabble.org/video/ngadc/vermeer-master-light-music-lesson-part-2, and a mirror Wink
http://www.artbabble.org/video/ngadc/vermeer-master-light-girl-red-hat-part-3
http://www.artbabble.org/video/ngadc/vermeer-master-light-camera-obscura-part-4, where the lens mentioned, instead of a pinhole, is used to keep the box smaller. Perspective is still dictated by the position of the entrance pupil of the Camera.
http://www.artbabble.org/video/ngadc/vermeer-master-light-woman-writing-letter-part-5

A Camera Obscura with pinhole doesn't have a field of view, it just projects an image on a surface, it's plain projection perspective. This is similar to human vision, where we can scan the scene with our eyes to get a wider view, or even turn our head for a panaoramic view, from a given vantage point. Only vantage point (and thus distance between objects) and direction of view play a role in perspective.

If lenses would be needed to mimick the vision of the old masters, then what lens would be needed to duplicate the result of, say, Vermeer's painting of the woman holding the balance/scales? Answer, whatever would give the same crop of the scene he viewed in front of him. Using a wider angle lens would require to shoot closer up, which would change the perspective (the relative size between foreground and background features), and the lines to the vanishing points would converge at different (less effective) angles. Although he understood how to manipulate perspective, he just used straight projection perspective in most of his works.

In this lecture about (amongst others) Vermeer's 'Milkmaid' (at about 0:26:40 into the clip), we can learn more about the hows and why's and the symbols of it, but at 0:53:03 we also get shown other uses of Vermeer's keen sense of realistic (photographically accurate) perspective (look at the size of the Cavalier's head relative to the more distant woman), and how a higher or lower horizon due to a different vantage point and distance to the subjects adds almost subliminal clues about shyness or admiration/superiority.

It is, and has always been, all about projection distortion, nothing to do with the FOV of lenses. However, we can use lenses to exaggerate the effect by 'forcing' us to look at the image from the 'wrong' distance (see the other thread I referenced earlier for a discussion about that).

Nothing new, it's just that some people are not aware, now they know ...

Cheers,
Bart

P.S. I've added 2 other photographs by Erwin Olaf as attachment, from a series to commemorate the libration of the city of Leiden on October 3rd, 1574, just for the fun of showing the style of the old masters being reproduced with modern equipment (the making of, mostly in the local language).
Erwin, with his wicked sense of humour, also added some contemporary accessories to the approx. 2x3 meter 'Liberty' composition. He added some bondage straps to one soldier's harness, had someone wear flip-flops instead of shoes or sandals, and strapped an iPod to one of the main figures' belt, to compensate for the people who had to eat cats and dogs to survive the siege while the plague was rampant. I love his sense of humour.
« Last Edit: June 16, 2012, 12:54:32 PM by BartvanderWolf » Logged
theguywitha645d
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« Reply #12 on: June 16, 2012, 11:41:47 AM »
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Are you interested in angle of view, then there really is no answer because it depends on what you are looking at and how you are looking at it. There is a great deal the mind controls over our perception. The visual system is more than an inflexible camera.

If you are talking about normal apparent perspective, then a focal length equal to the diagonal on the image format with the image viewed at the same relative distance will recreate the apparent perspective of the eye. Changes to either the focal length or viewing distance will give an apparent perspective that is not "normal." Hence the term "normal" lens. BTW, 50mm is not "normal for 35mm, but 43mm is.
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Ray
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« Reply #13 on: June 16, 2012, 10:57:59 PM »
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Hi Bart,
Well, that's a very long and convoluted post, and the Youtube video was really, really boring. For a moment I thought the lady was going to expose her breasts, but nothing so interesting happened, so I felt it was really all a waste of space.

I prefer simplicity in my arguments. I think it was Albert Einstein who said something to the effect, if a theory cannot be understood using simple descriptions and analogies, don't trust it.

As I recall, in the rather long, recent threads dealing with this subject, to which I hesitate to provide a link, we arrived at a distinction between a 'correct' viewing distance to a print, and a 'standard or recommended' viewing distance to the print.

This appeared to be a neat solution to the problem of the apparent change in perspective that results when one uses a wide-angle lens, a change which seems to be in contradiction to the adage that only position affects perspective.

Your argument seemed to go along the lines that any difference in perspective, compared with the real scene, that results when viewing a print from a wide-angle shot of that scene, is only apparent, not real, and is due to an incorrect viewing distance to the print.

Now I accept the concept that within a very narrow range of print sizes and viewing distances, one can compensate for such apparent changes in perspective that result from the use of different focal lengths of lenses, by altering one's viewing distance to the print.

For the benefit of those who are new to such concepts, if I take a shot of a cityscape using my D800E with 14mm lens, and make a very large print of the uncropped image, the huge cathedral in the centre of the image, which was very impressive from the same position I took the shot, when viewing the scene with my naked eyes, becomes very tiny on my huge print from the wide-angle shot.

Now you, Bart, and theguywitha645d, seem to think there's no problem here, regarding perspective. All you have to do is view the 3mx2m print of the city from the same distance you might read a book, say 300mm. The huge cathedral is then apparent in all its glory, provided you used a D800E to take the shot, otherwise it might be a fuzzy mess.

At such a close viewing distance, the objects on the print which are near the edges of the frame are in our peripheral vision, blurry and indistinct, just as in the real scene when our gaze was directed at the cathedral.

What a wonderful day for science. We don't have to scrap our theory that only position determines perspective.  Grin

Oops! There's a problem here, Houston. I can't get close enough to my postcard size print of my 14mm shot. The perspective is all wrong, and there's nothing I can do about it.  Sad

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theguywitha645d
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« Reply #14 on: June 16, 2012, 11:12:00 PM »
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Now you, Bart, and theguywitha645d, seem to think there's no problem here, regarding perspective. All you have to do is view the 3mx2m print of the city from the same distance you might read a book, say 300mm. The huge cathedral is then apparent in all its glory, provided you used a D800E to take the shot, otherwise it might be a fuzzy mess.

Actually, i would prefer you to view the image from about 3m away. That way the change to the apparent perspective you wanted because of the choice of the wide will be preserved. If you wanted "normal" perspective, you should have used a different lens.  Wink
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Ray
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« Reply #15 on: June 16, 2012, 11:51:01 PM »
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Actually, i would prefer you to view the image from about 3m away. That way the change to the apparent perspective you wanted because of the choice of the wide will be preserved. If you wanted "normal" perspective, you should have used a different lens.  Wink

Wow! Don't tell me you are admitting that a change in focal length of lens used, from a fixed shooting position, can change the perspective, or the relative size of objects, as seen on the print, compared with our  natural view of the real scene.

Should we now discuss the distinction between 'apparent' change in perspective and 'real' change in perspective.

May I suggest the following distinction. An apparent change in perspective, with change of focal length of lens, usually results when the viewer is a human being.

A real change of perspective does not necessarily occur if the viewer is an imaginary creature with perfect eyesight, perfect to the longest distance of the stars and galaxies (without use of telescopes), and perfect to the shortest distance used by our most powerful microscopes (without use of microscopes).

Does that make sense?  Grin
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duane_bolland
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« Reply #16 on: June 17, 2012, 12:48:42 AM »
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Reading up on Saccade led me here:

http://en.wikipedia.org/wiki/Fovea

So our sweet-spot for vision is about 2 degrees.  Obviously, we have a much wider field of view, but our acuity drops off quickly.

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BartvanderWolf
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« Reply #17 on: June 18, 2012, 09:24:46 AM »
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Hi Bart,
Well, that's a very long and convoluted post, and the Youtube video was really, really boring.

Too bad you feel that way. I hope that the OP did pay attention and now understands that the old masters, like Vermeer, chose a vantage point to paint from (or rearranged the scene). When a photographer shoots from that same vantage point, he will see exactly the same scene and perspective. He just uses the focal length of the lens to crop the scene for a given sensorsize, which results in a given Field of View.

The remainder of the equation, the viewing distance/angle which can distort apparent perspective, was covered in the other thread I mentioned earlier.

Cheers,
Bart
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David S
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« Reply #18 on: June 18, 2012, 09:50:05 AM »
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Thanks all,

Posts read and mostly understood. Also the various responses were appreciated for their differences as well as their similarities.

Dave S
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Peter McLennan
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« Reply #19 on: June 18, 2012, 12:42:24 PM »
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All very interesting.  But none of these posts answer the original question:  (what is the)  "angle of view of the human eye when fixed upon an object"

This should be easy to measure.  Lock down the eye's position, say by sitting the viewer in a chair.  Put various targets on a flat surface several feet away.  You could use sticky notes. 

Arrange them with one each at 12, 3, 6 and 9 as if on a clock face, with one at the center as the fixed target. 

While maintaining the fixed center as a "look at" point, either move the observer or the targets so that they are at the very edge of peripheral vision.

Measure the distances between the targets and from the center target to the eye.

The rest is simple trigonometry.
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