I seem to have 70 mm eyes - how weird am I?

[steve welle]

Have read in articles/books that human vision is approximately equivalent to 50 mm lenses (on full frame camera) as far as making a photo that looks to have the same perspective we see with our eyes. The CiC tutorial states that we have 43 mm focal length in this regard. With my 6D (full frame sensor) and previously with a 550D (1.6 crop factor), and with various lenses, every time I have tested this I am convinced the equivalent focal length is 70 mm. 50 mm makes things look somewhat "wide angle" to me, with things seeming a bit farther apart or stretched out from foreground to background, whereas everything looks more natural at 70 mm.

My questions:
Am I misinterpreting what is meant by those who state that human vision is similar to a 50 mm lens?
Have any of you noticed that things look more natural to you at focal lengths greater than 50 mm?
Is there a lot of variability among us in eye anatomy or visual processing that could explain this?

[steve welle]

one more thing I forgot to mention. I am nearsighted. Have read that one reason for myopia is the eyeball being too long. Is that why I have a longer focal length equivalent possibly?
Any other nearsighted CiC members with "70 mm eyes" please chime in.

[rpcrowe]

Steve,

I never felt that 50mm on a full frame camera was the way that I saw things...

I don't know about 50mm or 70mm "eyes" but, I am more comfortable using slightly longer lenses than using wide angle focal lengths. I generally just dislike the look of many wide angle shots and like the look of imagery shot with longer focal lengths. I shoot at least 1/3 of my general imagery (and all of my portraits - both dog and human) with my 70-200mm f/4L IS lens at various focal lengths on my 1.6x 7D cameras. The 70mm focal length would be equivalent to 112mm on a full frame camera and the 200mm would be equivalent to 320mm on a full frame camera. I use the gamut of focal lengths on this lens...

Additionally, I was very comfortable with the 28-135mm range of my first DSLR lens. I never felt too constricted by the 28mm (44.8 mm equivalent) side of that lens. , however, I did switch to a combination of 17-55mm f/2.8 IS and 70-200mm f/4L IS lenses for better quality and faster apertures and certainly don't mind the extra focal range...

[Manfred M]

Technically a normal lens is the diagonal of the frame, so for a full-frame camera this works out to 43mm (as per what you have read on CiC) and for a crop frame it is around 30mm.

The 50mm focal is really more historical as the first production model Leica used a 50mm Cooke Triplet design (f/3.5 ELMAX); EL = Ernst Leitz and MAX, from Max Berek, the lens designer), so 50mm (which is close to "normal"), stuck around and is with us today.

Just to confuse things, normal FoV for a person is around 180 degrees horizontally (thanks to having two eyes that are placed horizontally on our face) and 90 degrees vertically.

I'm myopic as well, but there are degrees of myopia, but mine is quite mild, so I really don't notice a lot of difference. I have never noticed any difference in the size of objects (with / without glasses), it's just that distance objects are not clear.

In my case, 50mm looks to be about right, but very slightly maginifed. 45mm seems to be just about right. I certainly do not see things at 70mm.

[DanK]

With my 6D (full frame sensor) and previously with a 550D (1.6 crop factor), and with various lenses, every time I have tested this I am convinced the equivalent focal length is 70 mm.

Your 70mm lens on your 550D has the exact same field of view as a 112mm would have on a 6D. So, if the 70mm seems 'normal' on one, it shouldn't seem 'normal' on the other. It's giving you a different field of view on the two cameras, and if you stand at different distances to compensate (e.g., to fill the frame on both cameras), you will be farther away with the crop sensor and will therefore have a different perspective.

[inkista]

For me, the whole 50-sees-like-the-human eye thing has nothing to do with FoV, and everything to do with magnification.

I.e., if you have a 50mm (ish) lens on the camera, and you bring the camera up to your eye, if you open your OTHER eye, the view matches between the two. You use a longer focal length, and the camera eye will see more magnification, a shorter one, and you'll see less. Doesn't matter what size your sensor is and the FoV that results. But the magnification matches, which is why oldtimers with non-taking-lens viewfinders used to prefer it--visualizing composition was then simply a matter of framing, not framing+translating for focal length.

One of the lenses I'm most comfortable with on my micro four-thirds (2x crop) camera is the 45/1.8. Not only is it right in my natural "short-telephoto" affinity range in terms of FoV equivalency (I tend to really love lenses in the 85-135 focal length range on my 5DMkII full frame), but it's also very close to normal magnification (i.e., 50mm). I often use it as a walkaround lens, despite the fact that the 20/1.7 is nominally closer to "normal FoV".

So, from where I'm sitting, not that weird to prefer a 50 even on a smaller (or I suppose larger) than full frame format.

[steve welle]

Your 70mm lens on your 550D has the exact same field of view as a 112mm would have on a 6D. So, if the 70mm seems 'normal' on one, it shouldn't seem 'normal' on the other. It's giving you a different field of view on the two cameras, and if you stand at different distances to compensate (e.g., to fill the frame on both cameras), you will be farther away with the crop sensor and will therefore have a different perspective.

Dan, sorry, what I meant was that the 70 mm equivalent of the crop sensor camera (about 45 mm) was the most natural. So I am getting the same phenomenon with both cameras.

[steve welle]

For me, the whole 50-sees-like-the-human eye thing has nothing to do with FoV, and everything to do with magnification.

I.e., if you have a 50mm (ish) lens on the camera, and you bring the camera up to your eye, if you open your OTHER eye, the view matches between the two. You use a longer focal length, and the camera eye will see more magnification, a shorter one, and you'll see less. Doesn't matter what size your sensor is and the FoV that results. But the magnification matches, which is why oldtimers with non-taking-lens viewfinders used to prefer it--visualizing composition was then simply a matter of framing, not framing+translating for focal length.

One of the lenses I'm most comfortable with on my micro four-thirds (2x crop) camera is the 45/1.8. Not only is it right in my natural "short-telephoto" affinity range in terms of FoV equivalency (I tend to really love lenses in the 85-135 focal length range on my 5DMkII full frame), but it's also very close to normal magnification (i.e., 50mm). I often use it as a walkaround lens, despite the fact that the 20/1.7 is nominally closer to "normal FoV".

So, from where I'm sitting, not that weird to prefer a 50 even on a smaller (or I suppose larger) than full frame format.

Kathy, thanks for the input. The reason I first noticed this issue was because the magnification for me was the same as my eye when the cropped sensor camera was a bit less than 50 mm, so about 70 mm full frame equivalent. Then when I bought a full frame sensor camera noticed that 70 mm was same magnification as my eye, no matter how near or far the subject. Then I started looking at how this translated into perception of foreground to background distances in the overall impression of an image and it was clear that 70 mm gave the best match with my eye's impression of these distances.

[DanK]

Dan, sorry, what I meant was that the 70 mm equivalent of the crop sensor camera (about 45 mm) was the most natural. So I am getting the same phenomenon with both cameras.

Thanks. I see now.

I have to admit that even though I have been using SLRs since 1968, I have never thought all that carefully about this--either what precise focal length seems most 'normal' to me or what precisely that entails (perspective, FOV). Sticking for the moment with the 35mm/FF format (I have both and a crop), it's always seemed obvious to me that substantially shorter than 50mm and substantially longer than 50mm are not my 'normal', but I never thought about where precisely the match is. You have me intrigued. At some point, I will take both of my bodies and play around to see.

[AB26]

Hi Steve,
How did you test your vision in comparison to what the camera sees?

[steve welle]

Hi Steve,
How did you test your vision in comparison to what the camera sees?

Andre: I am not sure I am testing this properly and that might be because I do not fully understand what is meant when people compare lens focal length the normal vision. For the most part I simply set the focal length on a zoom lens, look through the viewfinder, look at the scene with my eyes without the viewfinder, and decide whether the objects in the field of view appear to be the same size with and without the viewfinder. Since the viewfinder shows essentially the same frame as the viewfinder there is no need to take a shot. I checked with with objects both near and far. Further, I did the same thing and tried to evaluate subjectively the sense of depth in the scene by eye or through viewfinder. For this I also took some shots and inspected them carefully in comparison to standing there looking at the same scene. By sense of depth I guess I mean how far apart things in the foreground and background look to me, with short focal lengths making things elongated and long lenses flattening them as you all know. For me, about 70 mm is the winner in these comparisons.

It is very easy for anyone to test so I would be interested in how much variability among photographers there is in such comparisons even if my tests are not really getting at what is meant when someone says human vision is close to 50 mm focal length.

[AB26]

Andre: I am not sure I am testing this properly and that might be because I do not fully understand what is meant when people compare lens focal length the normal vision.

Ok Steve, try this:
Look trough the viewfinder with your right eye, in portrait mode, keeping your left eye open. Right eye sees world trough viewfinder and left eye looks at world in real time. Adjust zoom until both eyes see the same thing. Look at the set focal length. That would be pretty much the focal length your eyes see.

[DanK]

Someone can correct me if I am wrong, but I don't think size is the issue. It's perspective. Imagine that you put a 50mm lens on your FF body and compared the size in the viewfinder to the size with your naked eye. Assume it matches. Now add a magnifying element to the viewfinder. The image would seem larger, but the captured image and the focal length would both remain identical.

Short focal lengths exaggerate perspective (bulbous noses), while long focal lengths flatten it. I have assumed that a "normal" lens is one that roughly matches the perspective of the naked eye. however, this is just my assumption, and perhaps someone who knows more about optics can weigh in to correct me if I am wrong.

[steve welle]

Ok Steve, try this:
Look trough the viewfinder with your right eye, in portrait mode, keeping your left eye open. Right eye sees world trough viewfinder and left eye looks at world in real time. Adjust zoom until both eyes see the same thing. Look at the set focal length. That would be pretty much the focal length your eyes see.

Andre, did it your way and exactly the same result, 70 mm. What did you get?

[steve welle]

Someone can correct me if I am wrong, but I don't think size is the issue. It's perspective. Imagine that you put a 50mm lens on your FF body and compared the size in the viewfinder to the size with your naked eye. Assume it matches. Now add a magnifying element to the viewfinder. The image would seem larger, but the captured image and the focal length would both remain identical.

Short focal lengths exaggerate perspective (bulbous noses), while long focal lengths flatten it. I have assumed that a "normal" lens is one that roughly matches the perspective of the naked eye. however, this is just my assumption, and perhaps someone who knows more about optics can weigh in to correct me if I am wrong.

Dan: I think you are correct but the perspective also looks more correct to me at 70 than 50. Differences are more subtle though than when comparing size through viewfinder and naked eye.

[DanK]

I just tried, using a FF. I used focused on the front corner of a bookshelf, with the books running at a diagonal to give me more sense of perspective. I found it hard to do, because there are confounding factors--no boundary when you look with the naked eye, differences in DOF, and differences in size. And the perspective is not all that different at 50 and 70mm. However, it seemed to me that 50mm was closer to natural as I perceived it.

[ajohnw]

Have read in articles/books that human vision is approximately equivalent to 50 mm lenses (on full frame camera) as far as making a photo that looks to have the same perspective we see with our eyes. The CiC tutorial states that we have 43 mm focal length in this regard. With my 6D (full frame sensor) and previously with a 550D (1.6 crop factor), and with various lenses, every time I have tested this I am convinced the equivalent focal length is 70 mm. 50 mm makes things look somewhat "wide angle" to me, with things seeming a bit farther apart or stretched out from foreground to background, whereas everything looks more natural at 70 mm.

My questions:
Am I misinterpreting what is meant by those who state that human vision is similar to a 50 mm lens?
Have any of you noticed that things look more natural to you at focal lengths greater than 50 mm?
Is there a lot of variability among us in eye anatomy or visual processing that could explain this?

50mm sort of matched our acute vision field of view. Perspective gets correct at something like twice that. Basically the 50mm is a mild telephoto based on the diagonal of the format. 55mm has been used as well in the past. Also 45mm. It's a woolly subject in some ways but I have come across people in the past that could tell that a portrait had been shot with the once widely used 135mm lens at a glance rather than a 100mm. Go up to 200mm and it really will have an effect on the apparent length of some ones nose. I have often wondered if this was why some companies came up to others in the range 75-90mm.

There are some examples shown here - even though some seem to think the effect doesn't exist.

http://en.wikipedia.org/wiki/Perspec..._(photography)

John
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[steve welle]

Dan, thanks for running the test and the feedback. I agree the differences in perspective between 50 and 70 are subtle. The magnification test is the one with a much clearer result for me.

[steve welle]

John, thanks for the information and link.

[AB26]

Andre, did it your way and exactly the same result, 70 mm. What did you get?

55mm on my 1.6x crop camera = 88mm. Oops, another "freak".