50 mm "normal" not so normal perspective

[duane_goff2]

This is a rather fundamental question about the perspective of the foreground subject

in relation to the background. I am using the Nikkor 50mm 1.8 in a landscape

setting and noticed the same problem I was having with the 35mm wider angle lens

in that foreground objects "loom" in size while the background subject is reduced in

size and actually seems flattened. If I were to take my zoom lens and select 70mm

the perspective relation is more natural in that the backgrount is "normal" sized. I

suppose 50mm is acceptable if you are photographing a portrait with the subject in

front of you and background less important but I am doing the exact opposite. Is this

a particular aspect of this lens and there is a more normal lens available, or would

this be typical for a 50mm lens? PS: What I am actually doing is assembling a

panoramic of 10-20 photos in photoshop and noticed this problem, lens weight is a

factor. Any help greatly appreciated!

[brandonhamilton]

Agreed. Technically speaking, in realtion to how your eyeball sees, the 50mm could be considered wide angle. I also find between 60-70 looks the closest to what we see everyday with our eyes.

[frank uhlig]

All lenses of one focal length give the same perspective from the same spot.

 

You say "...the same problem I was having with the 35mm wider angle lens in that foreground objects "loom" in size while the background subject is reduced in size and actually seems flattened. If I were to take my zoom lens and select 70mm the perspective relation is more natural in that the backgrount is "normal" sized."

 

Thinking about this, I wonder how large the same foreground as on the 35mm or 50 mm lens photo would be at 70mm focal lens: HUGE.

 

Yes, longer lenses pick out less foreground and show the 'far off' more "equal sized". But if you include foreground equally, you will always have it larger appear than the background.

 

It is simply a physics law that the actual size of an object shrinks in direct proportion to its distance from the eye. 20mm lens or 200 mm lens make no difference. Just step back with the 50mm lens a bit (to decrease the foreground subjects a bit in size) and all will be more "normal" to you.

[scott_mcloughlin]

A 50 is a 50, at least in 135 format.

 

Otherwise, FL is a much discussed issue. Many folks argue that 35mm is pretty good for representing the eye's peripheral vision, while 70-90mm is good for representing the eye's object-focus oriented vision. And 35-85 or 35-90 is a pretty popular lens kit for many folks.

 

Quite a few folks call a 35 a "normal," but i personally don't see it. I find 35mm is really very wide and attribute its often purported "normal" status simply to the popularity of 35mm P&S cameras over the last few decades. Normal is really just "customary."

 

Technically, I believe the normal lens for 35mm 135 format film is something like 43mm, but that's based solely on film format.

 

I happen to like the 50's versatility. It provides me with some natural subject isolation (vs. a 35mm) and can provide reasonable enough tele duty at close focus for people pictures and the like. For wide, I've come to adopt the 28mm lens both for Nikon and Leica gear. 28mm is a true wide and brings some composition and framing challenges, but it's a pretty good all-around wide. I go to 21mm for my ultra wide needs (not Nikon gear).

 

Regarding short teles, I've shot both 85 and 105, and find them very different. While I've never experimented with the 65-75mm focal length, my 45/2.8 and 50/1.8 fall right in that range on my new toy D70. So I'm looking forward to exploring how the world looks through a very-short tele/very-long normal or whatever we should call this FL range :-)

[albinonflickr]

Frank wrote: "All lenses of one focal length give the same perspective from the same spot.".

 

In fact, it goes one step further: "All lenses from the same spot give the same perspective"!

 

To get a grip on that, think about a wide angle picture of a bird in a lot of branches. Crop the picture so that the bird is filling the frame and you'd have exactly the same image as if it was taken with a tele-lense! Except for obvious limitations in sharpness, as a result of limited resolution and grain/pixelsize. Stitching 70mm or 24mm images together as a panorama should therefore theoretically make no difference!

 

What makes a 50mm different from a 500mm is the angle of view - obviously. With 50mm or wider you will be able to squeeze more subjects in one frame *from the same spot* - from the smae perspective. THAT makes the difference. Referring to Duane's remark, "foreground objects "loom" in size while the background subject is reduced in size and actually seems flattened", in relation to things looking 'natural' in a picture, think about the following example: hold your fingers close to your face and focus on them. See how they 'loom' in size, in relation to the background. With such perspective, the human eye rather works like a wide angle!

 

regards

 

Albin

[leonard_evens]

There was just a similar discussion in the digital camera forum. Let me summarize what I said there.

 

The usual assumption is that the diagonal of the format is the normal focal length. Thus for 4 x 5, 150 mm, which is pretty close to the length of the diagonal of a 4 x 5 frame is usually considered the normal focal length. But for a variety of reasons, 50 mm has traditionally been considered normal for the 24 x 36 mm format used in 35 mm cameras, even though the diagonal is closer to 43 mm. I'll leave it to others to go into that, but note that 50 mm is only a trifle long using the diagonal criterion.

 

The natural question is what the rationale is for choosing the diagonal. This is the one I've seen. It is thought that most people are most comfortable viewing a print from the diagonal of the print distance away from it. Thus for an 8 x 10 print, that would be 12-14 inches, for a 16 x 20 print twice as far. You might get closer if you wanted to examine some detail, but if you wanted to look at it all at once, you would stay that distance away. But it turns out that if you want the same perspective when viewing the print as when viewing the original scene, that means the lens should also be about the diagonal of the format away from the film, which for most scenes is approximately the focal length.

 

If the focal length of the taking lens is longer or shorter than the "normal" focal length, then you have to place your eye correspondingly further or closer to the print for the same perspective. But you would still tend to stay the same distance from the print, which means that the perspective will appear distorted for other focal lengths. This is particularly true for short focal length lenses.

 

Of course, viewing a print inovovles many factors, one of which is how many prints one has looked at before and what one expects to see. So it is not surprising that some people would prefer the results of using longer or shorter focal lengths.

[duane_goff2]

Well here's a further clarafication of what I am seeing. Your point in space is fixed,

you can't move up or back when taking a picture. You survey the scene before you

and perhaps there are beautiful redrock rising majestically before you. Out comes the

50mm attached to your cameera and you place the viewfinder up to your eye and

everything changes. The object you want most in the picture shrinks and foreground

objects loom. You take the camera away and its back to normal. I find the 70mm

focal lenght to be normal in relation to what the hman eye sees! I can't crop the

image because I am assembling a series of images to make a panorama. Thanks for

your help.

[stephen hazelton]

When you combine your photos into a single large picture, in effect, you are turning your 50mm lens into a very wide angle lens, and getting the apparent distortion that comes with that such a lens.

 

A 50mm lens is "normal" when used on a 35mm negative. On 120 film it's a wide angle. On 110 film, it's a telephoto. What determines the effect is the angle of view, which you are increasing with the assembly of pictures.

 

Another way to look at it: Suppose you just make a 4x6 print from a single shot. You look at it from 10" away. Okay, that's your "normal" view. Now, you make a panoramic by taping 20 other pictures on each side of that print. Now, you can't view it from 10" anymore, you can't see it all. So, you move back and view it from 3'. Now, it's not that "normal" view anymore, because you changed the viewing distance.

[Ed_Ingold]

Traditionally, a 50mm lens is considered "normal" because it takes in an angle of about 50 degrees. Of course your eye doesn't clearly more than a few degrees, but scans continually to view larger subjects.

 

It is better to consider the "perspective" of the viewed image, which looks best at or closer than the focal length times the degree of enlargment. For an 8x10 print, thats about 16 inches, or arms length. The distortion of wide-angle lenses makes heads (spherical objects) look oblong in the corners at that distance. That effect disappears if you hold the print proportionally closer. There doesn't seem to be any "distortion" of this type when the focal length is longer, but the apparent depth becomes flattened.

 

Like you, I find that landscapes, particularly mountains, look more natural at 70-105mm than at 50mm. Again, your eye is able to concentrate on a relatively small, distant objects in real life. The longer lens helps portray distant objects in a more pleasing proportion, making them look more "real."

[dante_stella]

70mm only looks normal through a 0.75x viewfinder like the ones in Nikon high-eyepoint SLRs. If you jack up the magnification to 1.0x you will see that a 50mm is only slightly narrower than what you see with your eyes.

[david_h._hartman]

<strong>Normal: Conforming with, adhering to, or constituting

a norm, standard, pattern, level, or type; typical.<br>

</strong><br>

A Normal lens is a 45mm to 58mm lens for a 35mm camera. Getting a

way from this norm its the distance from the subject to the

lens that determines perspective, nothing else, nothing! What we

are looking at and why determines what is a normal angle of view.

We dont take in a view all at once. We scan with our eyes

and the whole view is assembled in the brain.<br>

<br>

For those looking to establish a consensus on a new definition

for the normal lens the best bet is a 28~80mm f/3.3~5.6 zoom

thats held together with sticky tape.

[arachnophilia]

actually, normal refers to the range of lenses closest to being normal with film size. 135 film has an image area of 24x36mm, and a simple pythagorean calculation will reveal that that is about 43 1/4 millimeters between it's furtherest two points.

 

in other words, a lens that casts a circle of light 43.26mm in diameter will most accurately portray the persective as the human usually sees it. the closest lenses made to "normal" are 45mm.

 

the range the eyes see is a different matter. my eyes see about 20-24mm worth of image, but no 20 or 24mm lens comes close to looking like the perspective i see. i compromise at 28mm, because it's close to the range i see while constraining the image enough to make good compositions, and without exagerating or distorting the perspective.

 

so my normal lens is a 28mm.

[david_h._hartman]

<em>"...in other words, a lens that casts a circle of

light 43.26mm in diameter will most accurately portray the

persective as the human usually sees it." --Jeff Locke<br>

</em><br>

This has be argued for decades and means little or nothing other

than its a convention that lost out to longer lenses.

Humans dont see a circular area they see a more or less

horizontal area and 43.27mm is the diagonal of a 24x36mm format

and nothing more. 43.27mm is not something that can be accurately

measured in a human nor can any angle of view that results from a

43.27mm lens on the 135mm format.<br>

<br>

The way a human sees, the angle of view, etc. depends on what

that human is looking at. We do not "see" with our eyes.

We take snap shoots as it were and they are assembled in the

brain into a complete view. Some people with certain brain

injuries see only the snap shoot and can not see a whole image.<br>

<br>

If looking at food, looking at a predator (feeling like food),

looking at a potential mate or a potential rival, the angle of

view gets much smaller. When looking for motion the angle of view

gets much wider.<br>

<br>

Were it not for the speed and DOF control (and price) issues a 28~70/2.8

or 35~70/2.8 could easily be the "normal lens." These

are often referred to as a "normal zooms." All 50mm

Nikkor lenses that I have specs for are actually 51.6mm.<br>

<br>

The "normal lens" for a monorail view camera is a 210mm

f/5.6 because of the common use of this camera for table top work.

The 210mm on 4x5 is similar to a 60mm on 135 format. The normal

lens for a 4x5 press and field cameras is a 135mm f/4.5 or f/5.6

as its easy to crop without much penalty. The 135mm on 4x5

is similar to a 40mm lens on 135 format.<br>

<br>

Regards,<br>

<br>

Dave Hartman.<br>

<br>

---<br>

<br>

Sorry about the bold above. It appears to glare. It should have

been italic.

[lex_jenkins]

I'd describe my visual field, relative to a lens, as approximately 50mm but with a panoramic effect of a sort - a full nearly circular pattern without the fisheye effect.

 

There are also considerable optical flaws at the perimeter that seem comparable to vignetting or falloff, spherical aberration, astigmatism, barrel distortion and others.

 

It's rather disorienting, trying to "see" the entire image before one's eyes as it might appear in a photo taken with whatever the normal lens is for a given film format. I suspect that the eyes actually "see" an image with far, far more distortion than is apparent but our brains do an amazing job of correcting the image.

 

One typical example is depth perception, which does not come naturally to an infant no matter what scientific studies may claim. One of my earliest memories - probably between the ages of 1 and 2 - is of riding in a car and seeing an overpass in the distance. The overpass was tiny and I couldn't imagine how our car was going to fit under it. As we approached I began to feel panicky, certain that our car would strike the overpass or, at least, become stuck under it.

 

After a few such experiences I began to develop a more refined sense of perspective, depth perception, motion tracking and other visual skills. So, at least in my opinion, these are learned skills and are not merely physical characteristics of the human eye. As such, any comparison of human vision to any camera lens is inherently impossible.

[markwilkins]

It's all marketing. What makes a "normal" lens "normal" is that (for various optical reasons that have nothing to do with perception) the simplest (and thus cheapest) lens design can be achieved when the focal length is equal to the diameter of the image circle. This is 43 mm or so for 35mm film, 90mm or so for 6x7 film, and so on. These are "normal" lenses because before zooms became so popular they were generally packaged with the camera.

 

Interestingly enough, these normal lenses in just about all formats use very similar lens elements and optical formulas -- they're just scaled up or down in size. They also tend to be the fastest lenses for any given format, though there can be exceptions, usually much more costly ones.

 

-- Mark

[andrew_somerset1]

"It's all marketing. What makes a "normal" lens "normal" is that (for various optical reasons that have nothing to do with perception) the simplest (and thus cheapest) lens design can be achieved...."

 

It's about time people stopped posting this canard. The reason does have to do with perception, and it was already posted above. It has to do with the perception of normal perspective when a print is viewed from the normal viewing distance.

[terry_scott]

In terms of perspective, I'd suggest 55mm or even 58mm is close to how the human eye sees things. But in terms of natural angle of view of the eye(s), go for 45mm or 40mm.