What lens focal length most closely resembles the perspective of the human eye?

  • For example, if I have a lens that is 16mm-50mm, which focal length would be the closest to the human eye's 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?

  • Guffa

    Guffa Correct answer

    8 years ago

    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.

    Oh, ok, gotcha! I'm looking at the Sony a77, with the 23.5x15.6mm sensor. I'm looking to get the 18mm-135mm bundle so I just wanted to make sure it's not gunna be too zoomed in for normal shots.

    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').

    @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.

    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?

    @MattGrum: You are mixing up cause and effect. The effect of choosing a "normal" focal length is that you get a specific field of view, it's not the specific field of view that defines the "normal" focal length.

    @MattGrum If the image from the 10mm APS-C lens was displayed not as a conventional photograph; but with VR Goggles that didn't restrict the users peripheral vision would the result then become 'normal'? Or to word my question differently, is the image considered abnormal because it's compressing data consisting of the entire human FoV into an small fraction of the FoV of the viewer?

    @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.

    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 .

    @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.

    I drew some cases on paper and you are right. in the end everything fits at the same distance. In that case I don't see why anyone would recommend using a 50mm on fullframe for portraits, as 50mm on aps-c is still too close.

    according to my calculations the DOF is 1.6x narrower on the FF than with apsc at same distance with the eq.f. lens.

    another conclusion of this is that you can take a fine portrait with a super wide angle lens if you keep the distance and crop it out the small face from the center of the image :)

    @MattGrum: You got that backwards also. The magnification doesn't have anything to do with what we see as a "normal" field of view. The magnification in the viewfinder is only there so that we see the image at a reasonable size. More info: http://en.wikipedia.org/wiki/Normal_lens

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Content dated before 7/24/2021 11:53 AM