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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'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?
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.
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.
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.
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.
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.
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.
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.
If a sensor diagonal approximates focal length, this suggests a rectilinear image with vanishing point perspective. Consider one vertical edge, and project a triangular surface from that edge to the the centerpoint of the image. Do the same from the opposite edge to the centerpoint. This presents something like a tunnel view of single vanishing point perspective. The triangle's angles projected to the centerpoint coincide with the diagonal.
Whether this has any isomorphism with the human eye, it does present a view amenable to the human brain. Image information feels maximized when it contains a perspective dimension that subtends the view's corners, with a vanishing point on a diagonal. By definition, if we see a vanishing point, nothing is hidden on that ray. If edges of a view symmetrically subtend the same vanishing point in view, they generate the largest possible viewing surface that has a vanishing point. The diagonal forms an edge of maximum surface area projected at a vanishing point.
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.
