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For example, if I have a lens that is 16mm-50mm, which focal length would be the closest to the human eye view? (I don't have a camera yet, so I'm just curious).

Would 50mm be more zoomed in than "normal"?

I imagine 16mm would be wider than the normal human point of view?

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8 Answers 8

up vote 14 down vote accepted

That depends on the sensor size of the camera.

"A lens is considered to be a "normal lens", in terms of its angle of view on a camera, when its focal length is approximately equal to the diagonal dimension of the film format or image sensor format.[4] The resulting diagonal angle of view of about 53 degrees is often said to approximate the angle of human vision"

So, for a full frame sensor (24mm x 36mm), about 45mm would be normal view. For an APS-C size sensor (15mm x 23mm), about 30mm would be normal view.

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n.b. the whole "angle of human vision" thing is utter nonsense, it even says in the wikipedia article you link to that human vision is more like 104 degrees (it later goes to claim that 53 degrees is the angle of sharp human vision, which is also nonsense and even if it weren't that value would still be meaningless as the brain does so much processing you aren't aware of any 'zone of sharpness'). –  Matt Grum Feb 13 '13 at 12:39
@MattGrum: The "angle of human vision" concept is only an attempt to describe in simple terms why we experience a certain focal length as "normal". It's not nonsense, but it's simplified and of limited use. –  Guffa Feb 13 '13 at 12:53
It's the wrong simple terms, though. We experience a certain focal length as normal due to providing about 1x magnification when mounted on an SLR. Field of view does not come into it. If it did why is a 10mm lens on APS-C not considered normal, when it provides a much better approximation of the human field of view? –  Matt Grum Feb 13 '13 at 13:25
@DanNeely all the talk of field of view depends entirely on how large you view the image and from what distance, this makes it a very complex issue, there are so many variables you'll never come up with a definition of normal if you try and base it on field of view. Instead I believe the concept of a normal lens comes from achieving 1x magnification when looking through the viewfinder, i.e. if you hold up your hand in front of the camera it appears the same size as if you were not looking through the camera. This just so happens to occur at 50mm on an SLR. –  Matt Grum Feb 13 '13 at 15:12
the FOV is human vision is close to 180 degrees... and to do that with a lens you need a fisheye. which doesnt give hte correct perspective. 45mm gives the correct perspective and sense of proportion on both full frame and apsc . –  Michael Nielsen Feb 13 '13 at 21:18

It depends on what you're asking exactly, if you're asking what focal length provides the same magnification as the naked eye (as in you hold your hand out infront of the camera and look through the viewfinder, your hand appears the same size as it would without the camera), then the answer depends on sensor size and viewfinder magnification, but the answer ends up being about 50mm for most full frame DSLRs with 0.7x viewfinder magnification, and about 45mm for most APS-C DSLRs with 0.95x viewfinder magnification.

If your asking what lens provides the same field of view as the human eye, then this question is even harder to ask, as human vision has no hard cutoff, the peripheries just get blurrier and the extreme edges are only sensitive to movement.

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When you look through a viewfinder, a lens at around 50mm focal length will show objects at the same size as when you look at something with your eyes. You could test this by looking through the viewfinder with one eye, and looking next to it with the other eye. When you close one of your eyes, you will notice that your sight does not change, regarding the size of objects. This applies to APS-C cameras, as well for full frame cameras.

However, the eye is a very special organ and it is sometimes difficult to compare it with a camera with lenses. The angle of view from your eyes is about 180 degrees. It is a common misconception that your eyes cover 50 degrees or something like that. They 'focus' on a smaller angle of view, but if you concentrate you can see things in your peripheral vision.

Example: look forward and keep your arms next to your head, then slowly turn your hand forward. You will see it becomes visible when it is somewhere beside your head, so your angle of view is around 180 degrees with both eyes.

To capture such a wide angle you will need a very expensive ultra wide angle lens that does not look very natural in a picture. This is due to the fact that your eyes can 'focus' on a much smaller angle (see Macula of retina). That is also the reason why humans/animals have to 'aim' with their head, not every part of the eye has the same resolution.

Because your eyes 'focus' on a smaller angle of view, photographers prefer to have a 50mm (fullframe equivalent) to show the same angle as your eyes when they are normally looking at something.

A 50mm lens equivalent is a well accepted 'standard', so a 35mm lens could be considered as standard on an APS-C camera, taking into account the crop factor. A 50mm lens on crop becomes rather tight and is more suitable for portraits, although that is just an opinion.

I hope this helps you.

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The human eye is a very complicated organ, which only sees clearly for an angle of approx 2 degrees of the field of vision. The eye moves constantly focusing on different areas & the brain receives signals & converts these signals into the complete view that we see. Our angle of view would be approximately 180 degrees (forward facing) and approximately 130 degrees up/down. Most of this area is out of focus. For the area that is focused, a 43.2mm lens on a 35mm sensor would give the closest approximate magnification as the human eye, including the same approximate depth of field, but the overall field of view would be narrower.

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How about on a 23.5x15.6mm sensor, what mm lens would give the closest approximate magnification to the human eye? –  trusktr Feb 14 '13 at 7:40
@trusktr that is the common APS-C sensor size, which is 1.6x compared to what we learned on 35mm cameras. 35 is the closest common prime lens size to "normal", and normal is an imprecise concept that is also context dependent so don't try and figure it out too accurately. Use 50mm or greater for portraits. –  JDługosz Dec 16 '14 at 9:31

I look at it simply this way -

I look through my D800E full frame with my 50mm lens and what I see in the camera is a tiny bit smaller than what I see with my eye therefore not magnified but reduced. I guess around 60mm but will try my 60mm tomorrow.

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Hi fstop, and welcome to Stack Exchange. Unfortunately, this has more to do with viewfinder magnification than with field of view, focal length, or perspective. –  mattdm Oct 13 '14 at 21:59

I recall looking through the viewfinder with one eye and around it with the other, figuring it would match at the "natural" size. It was about 55mm. But that's not necessarily right...

Plus it depends on the nature of the print! Look at the final print. Say, a 4 by 6 photo, at reading distance. Hold it up, keeping the distance to the eye the same, and it should look exactly like a wire frame (a window) would, in its original position.

So it depends on the size of the print and the viewing distance. Cropping changes that, meaning you need a shorter lens if you plan margins to crop later. The modern computer viewing is probably different than "print", and even 4 by 6 is not what was used to come up with that.

If you want people to not look funny, use a definite telephoto length.

The back of the eye is not flat, and the projection is not "corrected" (but the mapping of which pixel is where un-does the projection effect) so there's really no such thing without special equipment. However at reading distance the scanning of the macula over the "window" gives an effect that is pretty close to flat, except that you have two eyes and they can't both match at the same time, and the perception is corrected for eye placement vs head rotation axis and that shows visible differences if you trace a window vs hold up a normal photo.

But to be precise about what is meant, and to show that it's accurate, the "window" is the definition to use. That's what movie directors are doing when they hold their hands out to define corners of a frame.

If the print is held so that a person's face is life-size (put it where the window would be), it looks objectionable if you are closer to the print/window than you would be to look at the person normally.

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My understanding is that for the brain to percieve a photograph with the same perspective as it gets from the eye the focal length should be the same as the the diagonal on the image (film of sensor). This is about 43mm on "full frame" and 28mm on APS-C. Photographs taken with wide angle lenses tend to add depth to features, longer focal length tend to flatten the image. Portraits are generally considered more complimentary if facial features are flattened slightly, hence the tendancy for the slightly longer focal length usually prefered. The converse can be seen in the "uglyfication" often achieved with portraits taken on phone cameras.

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When I take a picture with my nikon d5000 with a 70-300 mm lens,i have to set it at 100 mm for the object in the picture to appear to be the same size as my eye sees it.

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So at the 300mm setting Im getting about 3x zoom, does that sound right? –  user35297 Dec 16 '14 at 5:42
Not even close. The viewfinder is not a direct view but has its own widening effect. 3x zoom would be (nominally, conventional) 100mm on that camera. –  JDługosz Dec 16 '14 at 9:28
Appear the same where? In the viewfinder? On the screen? In a print? –  mattdm Dec 16 '14 at 10:52

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