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Normal Lens: What angle of view = human vision?

Ron Wood , Nov 23, 1998; 01:06 p.m.

One of my loves is landscape photography. In attempting to replicate what I actually see I've discovered a couple of things: 1) in order to obtain an "angle of view" that corresponds to the human eye, I end up using a "wide" angle lens (28 mm in 35mm format). However, with that lens, the "perspective" is different than what I see. In order to get the in-camera "perspective" that more closely resembles human vision, I need to zoom to about 60 mm or so (in 35 mm forma; and not the quote 50 mm that is thought to be "normal;" Have thought that the discrepancy may be due to the fact that we see in "stereo." Please disregard any incorrect usage of the above terms, I welcome definitions.

Therefore, my question is: What's the best combo of format & focal lengths to use to dublicate human vision (or what we actually see)??

Thanks for any and all thoughts.

Ron Wood

Responses


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Mark Ci , Nov 23, 1998; 01:54 p.m.

This has been beaten to death here several times, but the real information has usually been lost in a sea of yahoo speculation, so I'll repeat it.

The "discrepancy" is not due to stereo vision. It's due to the fact that, to achieve natural perspective, a photograph must be viewed so that it covers the same angle of view as the scene did when the photo was taken. An 8x10 held at 12" from your face covers about a 45 degree angle, so to achieve natural perspective under this assumption, you need to use a lens that covers the same angle -- about a 37mm. Change your assumptions about print size or viewing distance and your "normal" lens focal length changes.

Karl Wessendorf , Nov 23, 1998; 02:25 p.m.

Ron, The "discrepancy you are finding between what you when "see" and what you "notice" when you look at your prints has a lot to do with ones brain. When you look at a tall building, it doesn't look like it is tilted back (as it would in a picture taken with a 28mm) because in this "live" situation your mind knows that the building is straight and erect. Try to frame a tall building within your hands next time you are out, looking at a building only as an image, and you will "see" the building leaning back. You have to overcome you're mind's natural correction. Another source of this perspective problem comes from the difference between where the shot was taken vs how the photo is viewed. (Viewing a photograph on center is rarely the shooters vantage point)(this creates a small, but real effect). My "normal" lens was 28mm, now it's 35mm because I like the trade off of a little less field of view for a little less exaggerated perspective. Your photos will always show more perspective "problems" than you will see. You're right about the 60mm threshold. From 60mm on up, one gets very little tilt (back or to center) with vertical subjects. This is the way your mind wants to see things. Since when viewing a photograph, your brain is limited only to what is in the picture, it has got to look "right". Regards, Karl

Karl Wessendorf , Nov 23, 1998; 02:32 p.m.

Yes, Mark has the other leg to my "shoot where", "view where" perspective problem. The distance at which one views a reproduced image is critical to an accurate recreation. Regard, Karl

Martin Tai , Nov 23, 1998; 07:11 p.m.

The human eye has a focal length between 13mm to 16mm; at outdoor the iris opening has a numerical aperture of between 3 to 4 but due to the short focal length, the eye has great depth of field. For a 35mm camera to imitate the eye viewing experience, a focal length of 45 to 60 and an aperture of f8 to f12.6 will produce image resembles the human eye vision. To reproduce the exact on situs perspective, the the picture should be view at a distance of 25 cm with a magnification of 25 divided by focal length; for instance with a 50 mm lens, the picture should be enlarged 5 times and viewed at 10". If you use a normal length, but with large aperture, you get the right perspective, but not the right depth feel.

Andreas Wickberg , Nov 23, 1998; 10:11 p.m.

Here is simple way to figure out what focal length corresponds to what you see. You only have to place your eye at the focal length distance from the image. That is, for a 24mm x 36mm picture and a 50mm lens, place your eye 50mm from the frame. If you magnify it 8x, look at the picture 8x50mm or 400mm from the page.

Martin Tai , Nov 23, 1998; 10:19 p.m.

In addition to what I posted in the previous message, if you really want to recreate the depth and perspective feel when you took the picture in the field, you should look at the enlarged picture (at proper distance ) with not two eyes, but only ONE EYE. One eye viewing of a picture provides a 3 D look, which though is not as strong as a truly stereo pair, but definitely better then viewing with two eyes.

Brian S. Dunworth , Nov 25, 1998; 08:07 a.m.

<I>"One eye viewing of a picture provides a 3 D look, which though is not as strong as a truly stereo pair, but definitely better then viewing with two eyes."</I><BR><BR> Umm... viewing something (live scene, picture, whatever) with only one eye eliminates depth perception. Depth would be the third dimension (width and height being the first two) in "3D". So, eliminating the perception of the third dimension (depth) would not, in any way, "provide a 3 D look" to anything.<BR><BR> Blocking one eye will, however, provide a nifty "2D" look... so you would be eliminating any poor mechanical attempt to approximate the human brain's depth perception by the camera's lens aperture and focusing mechanisms.

Martin Tai , Nov 25, 1998; 09:52 a.m.

Great Renaissance painter Leonardo da Vinci already discovered the one eye effect. He wrote: " Objects in relief, when seen from a short distance, with one eye, looks like a perfect picture" {Note books of Leonardo da Vinci Vol I p 21, Dover] Paraphrase: An photograph viewed at reading distance, looks exactly like viewing the real scene with one eye. Leonardo wrote further " Why will not a picture seen by both eyes produce the efect of relief as real relief does when seen by both eyes; and why should a picture seen with one eye give the same effect of relief as real relief would under the same condition of light and shade ?" Leonardo had a drawing to explain the reasons. Simply put, the two human eyes when viewing real relief, produces slightly different perspectives for each eye; this left/right eye differene does not exist when viewing a pciture; and when left/right eyes see exactly the same thing, the brain interpret the scene as 'flat', that is why viewing photogrphs with two eyes seeems flat, why viewing with one eye is no different as viewing true scene with one eye, the brain interpret is as 3D. Try it. Leonardo da Vinci 1452-1519.

Brian S. Dunworth , Nov 25, 1998; 10:59 a.m.

Martin,<BR><BR> I have no problem with what DaVinci wrote... he is, essentially, saying the same thing I said (or, more accurately, I have said the same thing he did :).<BR><BR> Your interpretation of what he said is what I believe to be in error.<BR><BR> A "3D" scene (live) viewed in "2D" (with one eye) closely approximates viewing a "2D" scene (a photograph) in "2D" (with one eye). You are (were) saying that closing one eye produces a "3D" effect. It does not, as (now) both I and Leonardo DaVinci have said.


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