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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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4 Answers 4

up vote 9 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"

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

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
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@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
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@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
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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
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@MichaelNielsen perspective is determined by subject distance not focal length / field of view. A 45mm - 50mm lens gives 1x magnification, that's why it is "normal", if that's what you mean by "sense of proportion" then that part is correct. –  Matt Grum Feb 13 '13 at 22:28
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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
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