Focal length of the human eye (related to 35mm)

What is the focal length of the human eye related to 35mm?

I heard that to get the picture with closest perspective to the one of the human eye, the focal length of the lenses should be set to the focal length of the human eye, is that true?

The human eye is kind of like a fisheye lens in that the field of view is close to 180 degrees. The brain corrects for things like distortion and perspective so that what you perceive is not what the eye takes in. I don't think there is a good answer to your question because it starts with the false premise that a camera can somhow reproduce this complex processing. It has been said that a 50mm lens on a full frame camera or 35mm lens on a crop sensor DSLR captures a similar perspective to the human eye. That isn't really true but it may be about as close as you will get.

I imagine that the focal length of the human eye is the distance from the cornea to the retina - 10-20mm????

To put the question the other way round, what focal length on a film camera or full frame digital camera roughly corresponds to what the human eye sees?

As the previous poster has said, it isn't that simple. However, I believe that the normal accepted figure is about 40-45mm.
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Chris R

The oft-quoted rule is that, in order to get the most human eye-like view in your photos, you should use a lens having a focal length equal to the diagonal measurement of the film/sensor. Hence Pentax's FA 43 Limited lens, having almost exactly the same focal length as the diagonal of 135 film.

On most cropped sensor DSLRs, the diagonal of the sensor is about 28mm.

Chris R-UK said:

I imagine that the focal length of the human eye is the distance from the cornea to the retina - 10-20mm????

To put the question the other way round, what focal length on a film camera or full frame digital camera roughly corresponds to what the human eye sees?

As the previous poster has said, it isn't that simple. However, I believe that the normal accepted figure is about 40-45mm.
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Chris R

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Some SLR cameras used to be supplied with a 58mm lens as standard. That seemed quite acceptable too.

Regards,
Peter

ibiza123 said:

What is the focal length of the human eye related to 35mm?

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There is no direct relationship, because of the different ways the two optical systems are operated.

ibiza123 said:

I heard that to get the picture with closest perspective to the one of the human eye, the focal length of the lenses should be set to the focal length of the human eye, is that true?

Click to expand...

No! Not even a little bit! And anyway, perspectives are a function of viewing position, NOT different focal lengths.

The human eye most closely corresponds to a sophisticated combination of TWO lens types, both at the same time. What's more, they couldn't be more different....

One is a super-sharp tele covering a very narrow angle of a few degrees only... something between 600mm - 1500mm equivalent, depending on the actual activity engaged in at the time of viewing... (dodging around on a basketball court, 600 or less: shooting hoops 1200 or longer.)

This super-sharp super-narrow tele lens is NOT fixed. Instead it SCANS around within a SECOND blurry wide-angle field of about 180°, very much like a fish-eye view ...

..... so, whilst the brain sequentially gathers what amounts to a wide-field and detailed view, only ONE PART of it is actually being "read in" at any one point in time. That is the point your eyeballs are scanning across....

.... just as you are scanning along this line as you read it, word by word, right now!

Yes, there is a lens that is half-way between very-wide and very-narrow acceptance; it is known as a "normal" or "standard" lens, equal in focal length to the diagonal dimension of the sensor it is used on.... in 35mm, something around 43 to 53 millimetres is cited.

Pictures taken with a normal lens do appear fairly "normal looking," one might even say boring, at least when enlarged to 10x8" and held at typical reading distance....

..... but it isn't because the normal lens is anything like the human eye, even though people do try to impose that quality upon the standard lens.

In fact the two optical systems could hardly be more different, especially after the brain's interpretative function has been applied to BOTH kinds of images... remember, every photograph you look at has to go in via the eyes! ;-)

As already hinted at, perspective is a different matter, and only indirectly connected to the focal lengths of the lenses we use in photography.
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Regards,
Baz

Well, I'll see your Cher, and your Streisand... and I'll raise you an Alice Babs!

Just a couple of recent threads discussing this topic:
http://forums.dpreview.com/forums/read.asp?forum=1018&message=35049839

http://forums.dpreview.com/forums/read.asp?forum=1018&message=35066602

... and I'm sure there are many more which could be found with a search for "50mm" and "eye".

Regards,
Peter

As the others have correctly pointed out the eye and a camera lens are very different things indeed.

Rather than concentrate on perspective, think about field of view. I have found that a 35mm lens on a 35mm sensor/film gives me a filed of view that feels very natural.

Kevin

it is theultimate in super zooms .. end of story .. sit at you lap top or PC or mac a foot from the wall ..your vision is much much wider then a 50mm ..

Cedarhill said:

The human eye is kind of like a fisheye lens in that the field of view is close to 180 degrees. The brain corrects for things like distortion and perspective so that what you perceive is not what the eye takes in. I don't think there is a good answer to your question because it starts with the false premise that a camera can somhow reproduce this complex processing.

Click to expand...

indeed. further, we may not actually CARE about FOV. we have central vision and periphery, which is not in focus. our brain filters all of this out, and though we perceive everything as focused correctly, it's because we're really only paying attention to where we're looking. and that attention is quite selective.

i found that, for my use, on film, 28mm represented approximately the angle of view to which i typically paid attention.

Cedarhill said:

It has been said that a 50mm lens on a full frame camera or 35mm lens on a crop sensor DSLR captures a similar perspective to the human eye. That isn't really true but it may be about as close as you will get.

Click to expand...

well, i don't know where that comes from, either. perspective is simply a result of subject distance, not focal length , so this statement is completely wrong. what it does represent is a lack of distortion (at the edges) as we perceive it, and similar magnification through the viewfinder.

For a similar perspective to the human eye you need something between 40mm and 55mm focal lengths in 35mm frame terms. I generally use the notional 43mm myself, which is roughly what you get with a 28mm lens on a crop frame camera.

Wikipedia has a article related to this.

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

This also might be of interest.

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

--
StephenG

Pentax K100D
Fuji S3 Pro
Fuji S9600

sjgcit said:

For a similar perspective to the human eye you need something between 40mm and 55mm focal lengths in 35mm frame terms.

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The human eye doesn't HAVE a perspective as such. Only viewpoints have perspectives, and human eyes are not fixed in their viewpoints any more than cameras are.

Besides which, as has been discussed at length, human vision is definitely not limited to the Field of View of a standard lens....

For both these reasons, a "normal lens" has no meaning in human vision terms.... and is strictly photographic.

Deleted1929 said:

Wikipedia has a article related to this.

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

Click to expand...

The Wikipedia article is wrong. It suggests that different perspectives are somehow imbued in different focal lengths. This is a fundamental mistake... and the article needs correcting.
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Regards,
Baz

Well, I'll see your Cher, and your Streisand... and I'll raise you an Alice Babs!

On the subject of the effective focal length of the human eye :

http://hypertextbook.com/facts/2002/JuliaKhutoretskaya.shtml

http://webphysics.davidson.edu/physlet_resources/dav_optics/examples/eye_demo.html

On the subject of humans vision not having a perspective I can only say that I personally see the world through a twined pair of sensors whose data is processed by my brain to generate what, in my mind, looks awfully like a viewpoint with a perspective.

If you feel the Wikipedia article(s) need amending then you're free to submit changes - that's how Wikipedia works. Bare in mind that you should respect both common meanings and technical meanings, not just one.

--
StephenG

Pentax K100D
Fuji S3 Pro
Fuji S9600

sjgcit said:

On the subject of the effective focal length of the human eye :

http://hypertextbook.com/facts/2002/JuliaKhutoretskaya.shtml

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The article is talking about ACTUAL focal lengths, not effective ones, and not in reference to any expected field of view.... (shrugs)

In any case, the actual focal length in millimetres of the LENS in the eye is irrelevant. The manner of seeing, and the way everything coming from the eye is interpreted in the brain to actually give us sophisticated visual perception, changes everything and makes a nonsense of any direct comparisons.

See my posting above....

http://forums.dpreview.com/forums/read.asp?forum=1002&message=36079539

My stuff apart, this has already been gone into at some length, not just here but many times in previous threads. Surely you couldn't have missed them all...[??]

http://webphysics.davidson.edu/physlet_resources/dav_optics/examples/eye_demo.html

In regard of what we are arguing about, I'm afraid that isn't helpful, either. Why are you snowing me with irrelevant stuff?

Deleted1929 said:

On the subject of humans vision not having a perspective I can only say that I personally see the world through a twined pair of sensors whose data is processed by my brain to generate what, in my mind, looks awfully like a viewpoint with a perspective.

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And it will be a different perspective if you stand somewhere else. Perspective is not in your eyes, not even in your brain, it is in WHERE you are....and that perspective exists in that place whether you are there to perceive it or not....

.... (shhhh ... I think there is a tree falling in the forest... No? Well, perhaps I imagined it! ;-) )

Deleted1929 said:

If you feel the Wikipedia article(s) need amending then you're free to submit changes - that's how Wikipedia works.

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It certainly does need amending. The article doesn't even MENTION viewpoint, for goodness sake! And I mean, not even once, not even a little bit!

Deleted1929 said:

Bare in mind that you should respect both common meanings and technical meanings, not just one.

Click to expand...

OK. But, with your permission, I'll "bear" it mind, thanks.
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Regards,
Baz

Well, I'll see your Cher, and your Streisand... and I'll raise you an Alice Babs!

Barry I don't actually care about this at all. Frankly I thinks it's utterly pointless trying to put one figure on such a vague concept - that's actually what the links I posted were intended to demonstrate.

It would be better if you stopped complaining to me about the Wikipedia articles. Better to consider actually contributing to them if you feel you're competent to. I'm actually trying to encourage you and others to do this.

--
StephenG

Pentax K100D
Fuji S3 Pro
Fuji S9600

sjgcit said:

Barry I don't actually care about this at all.

Click to expand...

I too have reached my boredom threshold.
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Regards,
Baz

Well, I'll see your Cher, and your Streisand... and I'll raise you an Alice Babs!

There is obviously more than one definition of the word "perspective" and to insist that only one is correct to the exclusion of all others ludicrous. There is the mathematical concept of perspective that graphic design students study. There is also the thing we also call "point of view" or what you might call "personal context" that has nothing to do with points in space at all. In order to identify a particular camera lens that comes closest to what the human eye sees, you have to take both of these concepts into account. That clearly isn't posible because of the reasons already mentioned.

As someone said, the concept is different. People always dissolve into arguing perspective Vs field of view. Field of view is how much you see in the frame, left to right. Perspective is how things appear front to rear.

A super wide angle lens makes things in the background appear further away then they are, a telephoto lens makes them seem much closer than they really are. But for humans we cant be easily fooled that way because we have two eyes, which gives us depth perception a single lens camera does not have. In 35mm format if you select a lens that makes perspective look 'normal' then the image looks cramped because of limited field of view.

In terms of the 35mm size ratio and common focal lengths a setting of 35mm will make things look the most normal as a compromise between balancing perspective (depth perception) Vs field of view (angle of vision). If you want more natural perspective you head towards 50mm, if you want more natural field of view you head toward 28mm.

But that’s for 35mm film format (and four thirds digital cameras). APS-C is a more elongated format that was designed to mimic a more natural human eye field of view (and be more appealing to buy because of it).

Midnighter said:

As someone said, the concept is different. People always dissolve into arguing perspective Vs field of view. Field of view is how much you see in the frame, left to right. Perspective is how things appear front to rear.

A super wide angle lens makes things in the background appear further away then they are, a telephoto lens makes them seem much closer than they really are. But for humans we cant be easily fooled that way because we have two eyes, which gives us depth perception a single lens camera does not have. In 35mm format if you select a lens that makes perspective look 'normal' then the image looks cramped because of limited field of view.

In terms of the 35mm size ratio and common focal lengths a setting of 35mm will make things look the most normal as a compromise between balancing perspective (depth perception) Vs field of view (angle of vision). If you want more natural perspective you head towards 50mm, if you want more natural field of view you head toward 28mm.

Click to expand...

You were doing so well, up until now...

Midnighter said:

But that’s for 35mm film format (and four thirds digital cameras). APS-C is a more elongated format that was designed to mimic a more natural human eye field of view (and be more appealing to buy because of it).

Click to expand...

APS-C has the same aspect ratio as 35mm camera film (and FF digital sensors). FourThirds sensors have the same aspect ratio as early video cameras (and early TV sets). The judgment about which of these two aspect ratios is most appealing is heavily influenced by cultural biases...often it's a simple as the more elongated 3:2 format being more "exclusive". I personally much prefer a square or almost square format...but I have never used an old 2 1/4" x 2 1/4" or 6cm x 7cm camera! SO, it's not a hangover from my childhood... ;-)

In my case it's simply an appreciation for good design. :-0

--
Charlie Davis
Nikon 5700, Sony R1, Nikon D50, Nikon D300
HomePage: http://www.1derful.info

"If ever a time should come, when vain and aspiring men shall possess the highest seats in Government, our country will stand in need of its experienced patriots to prevent its ruin."
-Samuel Adams, 1776

Thanks for the heads up. I blame sake...or spending too much time with my Mamiya 645, I am forgetting format ratios.