So what is a "normal" lens anyway?

[Evin Grant]

There has been alot of confusion lately about what constitutes a normal lens for the Red and it's different shooting formats. So lets start with a little history. In general a normal lens is one whose focal length is the same as the format's diagonal dimention. I've modified one of Brooks FAQ examples to illustrate.
http://www.reduser.net/evin/Eredformats.jpg
So you can see that the perfect normal lens for Red 4K is 25.5mm. By perfect I mean no wideangle or telephoto effect. By that calculation we can conclude that the normal lens for each Red format is as follows...

4.5K= 27.9mm
4K= 25.5mm
2k= 12.8mm
1080=11.9mm
& 35mm still (Film/Full Frame) is 43.3mm not 50mm as most think.

That brings up some other consideations though, it's generally believed that an 85mm lens on 35mm film is the lens of "Natural" perspective. This is because our visual cortex has the ability to narrow our preception when we concentrate on a face of person and that correspods well to the 28º angle of view of the 85mm (50mm shooting Red 4K) lens.

Here is an example of the 85mm f1.4 Nikkor on 35mm (Still) film.
http://www.evingrantphoto.com/people/krissy_p.gif

Conversley if you include the periferal vision the entire FOV of the human eye is closer to 14mm in the 35mm still format (8mm in Red 4K).

Here is an example from Flickr of 14mm Nikkor on 35mm (Still) film.
http://farm1.static.flickr.com/174/427095831_b4723c0dc6_b.jpg

This is one reason that changing lenses in mid shot (punching in) is a natural almost unnoticable edit. We do it all the time when we look at things. Of course perfect normal is not necessarily the lens we think of as normal, for almost 100 years the 50mm lens, which is ever so slightly telephoto has been the standard lens sold with 35mm still format cameras. Recently though the modern point and shoot compact has most often been fitted with either a 32,35 or 38mm lens. Slightly wide angle so this has become an increasingly more standard FOV. of course thses are all preceptions, the reason normal lenses were originally sold with cameras was thier ease of maufacture, from an engeneering prospective it's just easiest to design a good, fast lens that's the same as the diagonal of your format.

A Normal lens for Red 4K, the 25mm T1.3 Zeiss Master prime
http://www.fletch.com/images/25mmMaster.jpg

[jaadgy akanni]

Nice Evin, thanks. I appreciate this kind of info. I live and learn.

[ZzzZZz...]

Thanks for the input Evin...
btw. can you tell me how far away you where from the camera in your lense tests? mas y menos...

I will be shooting docs, so I guess the 28-70mm nikkor is going to be the standard lense for me... you said somewhere that it had a slight focus issue while zooming. Have you seen it for yourself? Is it serious even in the heat of things, or is it "barely noticeable"? Its an IF designated lense, so I had thought it wouldn´t be a problem.

Appreciate all your tests, they helped me a lot...

[Milan Nikolic]

Thanks Evin this is very usefull information. We all appreciate your work.

[snowmotion]

Using 2/3" sony B4 mounts had been my Plan But it seems silly to
not use the optimal res possible If I use 35mm lenses at 2k res am I then just using the Best part of the Glass and How will framing on moniters be affected?

[Lenny Manfred]

do you know the conversion factor for using 2/3 lenses with the b4 mount? for example, i kept my 10mm, 20mm, and 40mm digi primes to use with the Red, would these be wide, normal and telephoto, as they are on my 2/3" camera, or would they be something else? also, i am guessing they will work on 2k only, would this be a masked 2k or the whole imager, and will this affect sensitivity and/or perspective? i have a lot of questions, i know, i am just trying to decide if it makes sense to keep these lenses for this camera.

[Evin Grant]

lenny, you really need 35mm optics to take advantage of Red's true potential. Sell the Digi's and buy some Ultra primes or S4s, you won't regret it.

[durangotang]

I disagree (in a sense).

The diagonal of the sensor should be matched to the mm of the lens to achieve the proper PERSPECTIVE. A normal lens renders the perspective that the human eye sees, not the field of view. 50mm lens have been the standard "normal" lens for 35mm since the beginning, because it is close to the diagonal of 35mm film (or a full frame sensor). The trend now is more towards 35mm and zoom lenses in the digital SLR world, but this can hardly be called "normal" in the classical since of the word.

You are correct in that a 50mm lens is actually slightly more telephoto. Of the top of my head, I think 43mm is the true diagonal and delivers the same perspective as the human eye.

In considering what a normal lens is, it is essential not to confuse field of view and perspective. Although I do find the information about the 85mm lens being normal quite interesting for face portraiture, although in reality the perspective would seem to be off to me (for example the guy in the background in your photo would not appear to be that size in real life when your eye focuses on the girl).

I think what is needed is a redesigned larger format to remedy the perspective/field of view problem.

[chuck colburn]

Lots of pros and some not so pro (me) have considered a 38 or 40 mm lens as standard for full frame 35 still camera formatt for many many years.

[Finner]

Panavision 40 is one of my favorite lenses.

[Charles Angus]

I have heard that the brain goes some way to "linearizing" the size of objects; that is to say, making an object look 1/2 size when 2 times farther, as opposed to 1/4 size when 2 times farther.

Then there is the fact of our very narrow field of view in the area of highest resolution. While we have almost 180° of view, we have essentially no definition at the periphery.

I did some experiments sitting at my desk.

On my Canon 20d, 50mm replicates the size my headphones on my desk appear to my eye. However, my roommate on the other side of the room looks too small at 50mm; 58mm better replicates his size. I don't think anyone is suggesting that these are "normal" lengths on a crop sensor camera; I'm not.

At approximately 10 ft. 62mm replicates the speed of an object crossing the frame, and 52mm replicates the speed of an object coming closer.

In an ordinary sized room, to replicate the field of view I feel I can see with clarity, I think I would need about a 12-14mm (my lens only goes to 28mm). This would have to be cropped at top and bottom, as I see less detail there.

I can see only about 50mm worth of detail at 10ft.
The eye works very differently from camera's. For several different scenarios, I came up with what seem to me to be several different normal lenses.

Nothing can beat experience with how different lenses will feel in different scenarios, on different size screens, on different formats.

I feel academic debate about "normal" lenses is mostly moot.

[durangotang]

Well said Angus.

I always try to understand the math behind something, but in essence I suppose what is real subjectively is the most important.

I would really be curious to hear others do similar experiments, and see what their results are. And if a seasoned cinematographer could chime in (which I am not), one with the Red would be awesome, I am sure my eyes would be glued to the screen.

I want to purchase a Leica M8, and am trying to decide between a 35mm Summicron f/ 2.0 and a 35mm Summilux f/ 1.4 as my primary lens. This equates to 46mm with a 1.33 multiplier, which is pretty damn close to 43mm equivalent diagonal, and should yield a "normal" perspective for most work. The thing is that the Summicron is blistering sharp from corner to corner and has better contrast. The Summilux has a more creamy look, and is very subtly less sharp in the corners (in addition to having an extra stop). I have been going over different photos on each lenses Flickr group, and the more I look the more I see the different signatures of each lens.

And it is funny that you mention it, but I have been doing experiments with my eyes and trying to see what yields the most natural result. It seems to me that if I have an object in focus, at short distance (like my hand), I do have a lot of fall off of sharpness in the corners and periphery of my vision. A LOT. Obviously more than either lens. This scenario would equate more to aperture, though. If I focus on a wall, I still have loss of sharpness (although less pronounced). Even staring off into the horizon though, there is a selective area of focus in my field of vision. I wonder what that field of view is?

I am starting to ramble now...and if I don't stop comparing images on my computer screen I may go blind (which would negate the whole point)....

[Prem Edpuganti]

Good discussion. My needs are for a moderate wide to moderate tele. I am planning on buying the 18-50mm Red zoom. Would this be the equivalent of 30-83mm at 4K with reference to full frame 35mm, 43mm diagonal which is what I need.

[Disco Legend Zeke]

The field of view is not only in the eye of the beholder, it also depends on the beholder's butt.

If its plopped into row 1, the field of view will be very wide, in row 60 it will be narrow. There is only one seat in the theatre that gives the exact angle of view as seen by the taking lens.

If a movie is destined for 4K projection on a very large screen, we might choose a lens with a wider field of view than material shot for broadcast.

On the other hand, someone with BlueRay and a home theatre will have a seat much closer to the screen than most people in a movie theatre.

[Jorge Díaz-Amador]

This question comes up over and over again. There is no real answer, because the eye has different "virtual" focal lengths, depending on what you are concentrating on visually. I think the eye's true focal length is about 16mm, and the area of the retina is similar to the area of a 35mm film frame (interesting coincidence).

Here is my unscientific opinion:
For S35mm (24mm wide active image plane)

The full peripheral vision of two eyes (BTW women have more) = 10mm
"Normal" wide angle view = 14-18mm
Natural field of view and perspective in normal concentration = 40-50mm
FoV when concentrating on a specific object to see detail = 75-90mm

What I have noticed is that different focal lengths have a perspective that stays the same regardless of focal length. To me the most pleasing perspective is 85mm and the most natural is 40mm. And it's true in S16mm, S35mm and even VistaVision (Leica frame still).

[Jason Sinclair]

For me it's about perception. The human eye can see 180 or it can see macro depending on what the mind wants to see. (Night sky looking at stars to watching an ant carry food) Walking down the street you would go wide and when you see something that catches your eye you cut in and focus on say a woman walking by. If you look at her head you will get a good 85mm, that's why I suppose everyone says that is the standard because we love looking at people both from a voyeuristic perspective but also from a subjective perspective. How many times in film are we really seeing from the protagonists POV; the person we identify with? When two people are involved intimately it's generally 85mm (in 35mm film), more so when they are talking with each other.

So it's best not to look at it from sitting at a desk but rather what it is your protaganist looking at? or what is the story element or plot line being observed. Now if you are sitting at a desk looking at words on a computer (I'm taking an educated guess that's what you are doing) then you are looking at like a 300mm, but say you sit back and reflect and see the room around you you automatically go to 15mm or so (you can even do this whilst reading). The story we are telling is about a person who is trying to work out the difference between mathamatical equations and the emotions of true experience, so he looks away from the screen and sees a collection of small cards on the wall, (24mm) and then focuses on one in particular and reads the words on it. It reads "follow the magic in your heart it is the inspiration for your life" (100mm) He then realizes that it really depends on the circumstance and continues to read the words on the page...


It's not a static view, it's a fluid experience and it is wholly dependent on the story and the percpective of the voyour (traditionaly the director) and good directors use a character of whose eyes "we" look through. Writers have done this for centuries so it's really an extension of imagination. Say for instance i say there is a woman sleeping in bed with silk sheets, you might get a shot in your mind of 25mm or there abouts and i continue the story, "she is very bueatifal" you probably go 80mm "and she has georgous brown eyes " (200mm macro) and you can imagine it all with those shots in mind while reading words on a page. Really as film makers we are replicating this experience, this universal experience caled life that combines not only reality but imagination as well. The reality we all share that includes the reality of what is and what is observable but also the emotional and subjective experience of what we do with that information. Our own individual experience and particular needs etc..


As far as wether someone watching this on a big sceen from front row or back seat or on a hdtv or on an iphone really doesn't matter because the viewer uses their perception and imagination to adapt and will see the same story. Who still can read a book and enjoy it? No lenses needed.

I think in technical arenas it's important to keep your mind on the forrest while looking through the trees...

[David Rasberry]

Is perspective not consistent for a given focal length? By that I mean the perceived distance relationship between viewer and object and between different objects in the field. For example, I have an old Graflex 3-1/4 x4-1/4 press camera with a 52mm Schneider Grandagon that gives a 92 degree field of view with almost no distortion and , to my eye a slightly stretched perspective. By comparison the 14mm Nikkor shot above shows a very stretched perspective and significant distortion. Stick a 2/3" sensor in the middle of that Grandagon' s field and you would only get a 12 degree FOV but the perspective should be the same. I think something in the 80mm range more closely matches natural depth perception, even though the eye covers a very wide field of view. But it is hard to equate. Wide field of view mapped to a flat image plane I guess will distort perspective compared to the eye's curved image plane.
It would be an interesting experiment to try a curved plane sensor on a camera.

[Andres Papousek]

This are my point of view.

If we asume that e normal lens is the one that give us the most similar viewing experiense than with naked eye then forget frame size, forget focal lengh and forget field of view.

The first change with cameras the second and third depends of perseption and "mind games" or concentration.

But we still have something that are "allways the same".

(Hope you follow me cause English is not my lenguage.)

I talking about "perspective proportion" Let me try to explain.

Im siting in a chair at a class room (in the back of it cause don study to much). In front of my theres a beatyfull brunete that don't talk to my cause im a losser. Beyond is the teacher at the front of the class room.

Now I will tell you this is a BIG class room so the image of the teacher (from head to feets) that forms in my retine has the same size of the beautifull head of the brunete in front of my.

If I take a pic with a telefoto of the head of the brunete (close up) the teacher will incrase in size and Is a take the pic of the head of the brunete with a wide angle the teacher will get small mabe the size of her pearl earring.


Between those there is the Saint grial of lenses: "the lens that sees like the naked Eye" "The Normal Lens"

What do you think about this?

This is a great forum! I'm enjoying it a lot

Andres Papousek

[Stefan Christou]

This was a great thread. So to resurrect it somewhat... a normal lens for Epic or Scarlet S35 will be 33.5mm right? So the 35mm RPP will be closest to that, although slightly telephoto.

Looks like durangotang may have got his wish with Epic 645:


I think what is needed is a redesigned larger format to remedy the perspective/field of view problem.

I agree, but 645 is a bit out of my budget! :head_explode:

[Eki Halkka]

I disagree (in a sense).

The diagonal of the sensor should be matched to the mm of the lens to achieve the proper PERSPECTIVE.

And i disagree a bit more ;-)

Perspective does not change at all when you change focal length. Only the field of view changes.

Moving camera (i.e. to match framing) is the only thing that changes perspective photography wise.


A normal lens renders the perspective that the human eye sees

...and so do all other lenses, as (this is worth repeating) a change in lens length does not change the perspective.

The same goes with field of view - any field of view can be "normal".

A shot taken with a wide angle lens, enlarged to a big print which fills your view will match what the eye sees. A shot taken with a telephoto, print out to stamp size will do the same (when watching from the same distance).

A "normal" lens shot watched on a normal size from a normal distance will also roughly match your eyes.

It all boils down to how big the final image will be, how much of your field of view it fills.

[David Quinn Carder]

This whole debate annoys me. When we view the world with our naked eyes, in order to see a different part of the image, we move our eyes. When we watch something that has been recorded with a camera, we can look at different parts of the image. In other words, our "natural vision" always has our focus centered on the center of the image, but viewing a recorded image, we can focus on the peripheral.

So even if our eyes had a seriously wide-angle effect going on in our peripheral vision, it's not the same as looking at the edge of a wide-angle image.

[Humberto Rivera]

The question of a “normal lens” got me to thinking about a class that I gave to students quite a few years ago. Actually about 30 years, take or give a few. IN MY HUMBLE OPINION THERE IS NO SUCH THING AS A NORMAL LENS. Let me explain.

Generally human vision is composed of a series of rectangles, the exact number I really don’t know, but for arguments sake let’s say there might be 100. Looking at a wide vista one might need to spread them out over a huge field, thus the lack of resolution, but nonetheless there is enough to see what’s going on. On the case of the tiny “ant”, the rectangles kind of go right on top of each other; there is resolution, concentration, and thus the narrow field of view is really good.

All of this happens in your brain, just like breathing, or reaching out for whatever or whenever other natural instantaneously things occurs within the human body that don’t require you to think too much or none at all, it’s just simply a natural reaction that we’ve become adopted to doing.

Then there is panning, it’s a continues motion of the camera (or the head) from left to right, or from right to left. There is the movement from looking down to looking up, sometimes opening to a wider vista.

Now in a movie, in order to interpret what we see of feel, we’ve got to use different types of lenses, from the wide angle to the extreme close up. And like in real life, we must go from one to the other with a fluid motion, when it’s done right we do not see the change, it’s just kind of normal to see it happening. We transcend time and space, in minutes or in hours. We take time and space and slow it down, or make it go fast, or normal speed. Movies are a human’s representation of a story we are telling, so we can do whatever is good for the story, and when it works, it really works good.

So what is a Normal Lens, it’s whatever is required at the moment that we chose to use it to represent reality. Not the actual thing that we live every day, every second, but a representation of it. I always go back to Citizen Kane; it begins with the ending, then a documentary about him, they a series of stories told about him, then the story.

Humberto Rivera

[Yousuf Abbasi]

Then there is panning, it’s a continues motion of the camera (or the head) from left to right, or from right to left.

I think it is very difficult for our eyes to "pan" like a lens would, mainly because our eyes (and mind) have a tendency to focus on discrete objects thereby limiting a continuous panning motion. Try it out, see if you can pan the room smoothly by moving your eyes right to left (moving your head right to left does not necessarily mean you are panning anything, as focus can stay fixed). What you will notice is that your sight is sticky, and the panning is non-continuous, unlike the smooth pans that lens/cameras are capable of. That's because, like David Mullen told me, a lens/camera is dumb.



Now in a movie, in order to interpret what we see of feel, we’ve got to use different types of lenses, from the wide angle to the extreme close up. And like in real life, we must go from one to the other with a fluid motion, when it’s done right we do not see the change, it’s just kind of normal to see it happening.

In terms of what is a "normal" lens, I believe that is based on a focal length which is fixed in humans. In other words, we as humans can't just "zoom in" to whatever focal length we want. What you are referring to in your post seems more related to focus and depth of field, which indeed do change fluidly in human sight based on what you are looking at -- similarly, in a camera, you don't need to change into various focal lengths to mimic sight, but rather just adjust the focus.

Depth of field, however, is related to the particular person's eye sight. I, for instance, am very near sighted and without my contacts I have an extremely narrow depth of field. Someone with better eye sight than me probably has a much wider DOF.

Just some things I've thought about over time.

[David Rasberry]

Here is my unscientific opinion:
For S35mm (24mm wide active image plane)

The full peripheral vision of two eyes (BTW women have more) = 10mm
"Normal" wide angle view = 14-18mm
Natural field of view and perspective in normal concentration = 40-50mm
FoV when concentrating on a specific object to see detail = 75-90mm

What I have noticed is that different focal lengths have a perspective that stays the same regardless of focal length. To me the most pleasing perspective is 85mm and the most natural is 40mm. And it's true in S16mm, S35mm and even VistaVision (Leica frame still).

I mostly agree with this, epecially the last part about perspective, with the correction that perspective, i.e perceived depth separation of objects, stays the same with a given focal length regardless of field of view. For me something in the 80-90mm range has the closest correlation to accurate depth perception, but then I am very near sighted so maybe my eyes are just naturally a longer focal length.:devil:

[David Quinn Carder]

I think it is very difficult for our eyes to "pan" like a lens would, mainly because our eyes (and mind) have a tendency to focus on discrete objects thereby limiting a continuous panning motion. Try it out, see if you can pan the room smoothly by moving your eyes right to left (moving your head right to left does not necessarily mean you are panning anything, as focus can stay fixed). What you will notice is that your sight is sticky, and the panning is non-continuous, unlike the smooth pans that lens/cameras are capable of. That's because, like David Mullen told me, a lens/camera is dumb.

In terms of what is a "normal" lens, I believe that is based on a focal length which is fixed in humans. In other words, we as humans can't just "zoom in" to whatever focal length we want. What you are referring to in your post seems more related to focus and depth of field, which indeed do change fluidly in human sight based on what you are looking at -- similarly, in a camera, you don't need to change into various focal lengths to mimic sight, but rather just adjust the focus.

Depth of field, however, is related to the particular person's eye sight. I, for instance, am very near sighted and without my contacts I have an extremely narrow depth of field. Someone with better eye sight than me probably has a much wider DOF.

Just some things I've thought about over time.

Exactly.

I'm interested in buying a Scarlet 2/3" Cinema with a "normal" mini-RED Prime lens. When I say normal, all I mean—and all that's practical to ask for—is a lens which creates the least perceivable distortion, whether it be in the relative sizes of objects at various distances, or skewing of perspective. I want a ballroom in my recording to look similar to the way the ballroom looks in person—I don't want it to look bigger, the way the photographs for an apartment you're looking to buy make the rooms look bigger when taken with a typical wide-angle point-and-shoot.

I think any debate beyond that may be interesting, but it's not practical. A normal lens is a lens that makes things look "normal".

Incidentally, which of the mini-RED Primes would you recommend for the Scarlet 2/3" Cinema?; and will I be able to buy it without buying the entire set? For my purposes (not to mention my budget), I don't want multiple lenses, but I don't want the fixed zoom lens either. That may be an unorthodox approach . . .

[Humberto Rivera]

“Depth of field, however, is related to the particular person's eye sight. I, for instance, am very near sighted and without my contacts I have an extremely narrow depth of field. Someone with better eye sight than me probably has a much wider DOF.” Yousuf Abbassi.

Yousuf you are absolutely right, we are all different, so we have a different experience, that’s why a “Picture” might work for someone and not the next person. When we look at a distance object we might want to use a pair of binoculars to bring the image in closer or a 300mm lens on a camera. Yet when pieces of “Time” are being juxtaposed from one shot to the other it might seem just like the right thing to do. It’s a matter of perception, subconscious perception. It’s also a matter of choice by the filmmaker!

BUT on the screen we all get to see it the same “Movie” the same way because it’s ONE persons “interpretation” of a moment in “Time”, and in a film we must all consume that moment as “that person” saw it. It’s not real; we only think that is real, because of the skill of the filmmaker in elongating time or shortening “Time”. We try and get it right in terms of how we see the image on the screen, glasses, no glasses for those to see the movie, whatever it’s necessary, but our brains are going to act different base on our experiences.

That why I don’t belief in “Normal Lenses”, I do have a preference for the wider lenses, but it’s only a preference. Finally I chose the lenses that it’s going to make my story right, my interpretation of time, many things go into a movie, the period, what the space dictate, the list goes on and on.

Humberto Rivera

[kinokamera]

For what it's worth, I find that perspective wise, 50mm lens is a normal lens. Normal being that it sees the way our eye sees, i.e. perspective changes in the same way and the objects in the foreground are in the same relationship size wise to the objects in the background. Easy way to check this is to grab your still camera [or a director's viewfinder], pop a 50mm lens on it, look through it with your right eye, open your left eye - and the images will align perfectly, apart from the focus. Put a shorter lens and you cannot align it with what you see. Same goes for longer lenses. I did this test with my Leica R and

As far as I know this should hold over all formats, the size of the format would only determine the area of coverage.

Does this make sense?

[David Quinn Carder]

For what it's worth, I find that perspective wise, 50mm lens is a normal lens. Normal being that it sees the way our eye sees, i.e. perspective changes in the same way and the objects in the foreground are in the same relationship size wise to the objects in the background. Easy way to check this is to grab your still camera [or a director's viewfinder], pop a 50mm lens on it, look through it with your right eye, open your left eye - and the images will align perfectly, apart from the focus. Put a shorter lens and you cannot align it with what you see. Same goes for longer lenses. I did this test with my Leica R and

As far as I know this should hold over all formats, the size of the format would only determine the area of coverage.

Does this make sense?

I think so . . .

So you're saying that a larger sensor/format just means there will be more image, further out from the center, than a smaller sensor/format? But that regardless, the lens alone is what determines the distortion at the center of the image (like the size the moon compared to a subject's silhouette)?

Is that right? That makes sense to me, but I have very little hands-on experience or technical knowledge about how cameras work.

It would explain why I hardly ever take the 50mm prime off my Nikon D50—it just looks right when I look through the viewfinder and pan around. Doing the same thing with the wide-angle zoom lens makes me sick.

[Yousuf Abbasi]

For what it's worth, I find that perspective wise, 50mm lens is a normal lens. Normal being that it sees the way our eye sees, i.e. perspective changes in the same way and the objects in the foreground are in the same relationship size wise to the objects in the background. Easy way to check this is to grab your still camera [or a director's viewfinder], pop a 50mm lens on it, look through it with your right eye, open your left eye - and the images will align perfectly, apart from the focus. Put a shorter lens and you cannot align it with what you see. Same goes for longer lenses. I did this test with my Leica R and


I think what you're saying is true for still photography, or video to be viewed on a monitor directly in front of you. But for motion picture to be viewed in a large theatre, a "normal" picture means you have to choose a longer lens to compensate for the distant seating in the theatre (i.e. ~85mm focal length, in a large theatre, could be considered normal). In other words, normality is related to how the viewer sees the image, not the filmmaker.

[David Quinn Carder]

I think what you're saying is true for still photography, or video to be viewed on a monitor directly in front of you. But for motion picture to be viewed in a large theatre, a "normal" picture means you have to choose a longer lens to compensate for the distant seating in the theatre (i.e. ~85mm focal length, in a large theatre, could be considered normal). In other words, normality is related to how the viewer sees the image, not the filmmaker.

I don't see how this is true at all. The size of objects relative to each other in an image has nothing to do with seating distance. If a man (the subject) has a head that appears on screen to have a pixel diameter of X, and the moon in the sky behind him has a pixel diameter of 4X (due to the use of a telescopic lens), that's not "normal". The moon looks bigger than it does in real life, and likewise, if the shot was panned, there would be an illusion of speed with distant objects like the moon or the horizon that you can't replicate in real life without the use of a lens (like a telescope or binoculars).

When it comes to perspective, I think that gets thrown out the window when the size of the image doesn't sync up with real life. In other words, if you are watching a human subject on an enormous screen, his gigantic proportions are being compensated for, along with the perspective to match the size of the image, and even where the image is in the room. It's pretty simple for our brain to sort out.

ON THE OTHER HAND, the effects that wide-angle or telescopic lenses have on the image itself, regardless of where the viewer is sitting, do create effects that are clearly "movie-like" or "photographic", such as the skewing of the peripheral with a wide-angle lens, or the increased or decreased sensation of speed (depending on the lens and what you're doing with the camera), or the aformentioned changes in the relative size of objects in the foreground and background.

So I actually disagree with your statement, and would say that a normal lens is "normal" from the perspective of the filmmaker.

[David Mullen ASC]

I think what you're saying is true for still photography, or video to be viewed on a monitor directly in front of you. But for motion picture to be viewed in a large theatre, a "normal" picture means you have to choose a longer lens to compensate for the distant seating in the theatre (i.e. ~85mm focal length, in a large theatre, could be considered normal). In other words, normality is related to how the viewer sees the image, not the filmmaker.

The opposite actually tends to be true -- when an image is viewed on a very large screen so that it fills the peripheral vision of the viewer, like in an IMAX theater, you would compensate by using wider-angle lenses because the viewer is basically concentrating on the center inside the overall frame and thus is mainly seeing a more telephoto perspective inside a wider-angle frame. This is one reason why IMAX photography often resorts to wide-angle optics, and even the Cinerama process had an extremely wide angle of view (146 degrees or so). The image as a whole is very wide-angle but the edges of the frame are supposed to lie within your peripheral vision and you are supposed to concentrate on the more "normal" perspective inside. When the images are viewed on a small screen, they look too wide-angle.

You can see some of this effect in the Todd-AO production "Around the World in 80 Days", which tried to mimic Cinerama's wide view (from using three 27mm lenses on three negatives) with a single lens on a 65mm camera:

http://www.davidmullenasc.com/atwied1.jpg

http://www.davidmullenasc.com/atwied2.jpg

http://www.davidmullenasc.com/atwied3.jpg

Though the barrel distortion is quite extreme, on a large curved screen where you would tend to concentrate on the center, it feels less distorted.

[David Mullen ASC]

Here are some frames from the 3-camera Cinerama production "How the West Was Won" (I took these off of the old DVD and created the fake curved screen effect -- the new Blu-Ray has a "Smilevision" version on it):

http://www.davidmullenasc.com/htwww1.jpg

http://www.davidmullenasc.com/htwww2.jpg

http://www.davidmullenasc.com/htwww3.jpg

http://www.davidmullenasc.com/htwww4.jpg

You see that the basic principle behind Cinerama was very wide-angle image on a very large curved screen to create an immersive "you are there" experience where the side information sort of wraps around your vision. You'd have to use something like a 9mm lens on a Super-35 camera to get a similar horizontal view.

[Yousuf Abbasi]

I don't see how this is true at all. The size of objects relative to each other in an image has nothing to do with seating distance. If a man (the subject) has a head that appears on screen to have a pixel diameter of X, and the moon in the sky behind him has a pixel diameter of 4X (due to the use of a telescopic lens), that's not "normal". The moon looks bigger than it does in real life, and likewise, if the shot was panned, there would be an illusion of speed with distant objects like the moon or the horizon that you can't replicate in real life without the use of a lens (like a telescope or binoculars).

When it comes to perspective, I think that gets thrown out the window when the size of the image doesn't sync up with real life. In other words, if you are watching a human subject on an enormous screen, his gigantic proportions are being compensated for, along with the perspective to match the size of the image, and even where the image is in the room. It's pretty simple for our brain to sort out.

ON THE OTHER HAND, the effects that wide-angle or telescopic lenses have on the image itself, regardless of where the viewer is sitting, do create effects that are clearly "movie-like" or "photographic", such as the skewing of the peripheral with a wide-angle lens, or the increased or decreased sensation of speed (depending on the lens and what you're doing with the camera), or the aformentioned changes in the relative size of objects in the foreground and background.

So I actually disagree with your statement, and would say that a normal lens is "normal" from the perspective of the filmmaker.

Thanks for the feedback. You have a point that image size can be blown up or shrunk down, so in that sense normality is really from the photographer's perspective, not the viewer's. But this is interesting, because then it only seems like normality applies through the lens, not really on the projector or screen. Once images are blown up or shrunk down, how then do we judge what is normal? This discussion has really made me re-think the whole notion of normal lenses.

@ David Mullen: I also understand that in an IMAX setting, it makes sense for the viewer to be able to see a wider angle of view so that his focus is not just zoomed into a large image, hence the use of wider lenses. But isn't this more related creating a better movie-viewing environment for the viewer, rather than creating a "normal" look for him? The reason I thought a longer lens would make for a normal image for the viewer is because if, say, the image represents a man standing right in front of you, using an 85mm lens makes the man seem closer to you given that you are sitting further away in a movie theatre. Of course this wouldn't make for a very pleasing movie to watch, being so zoomed into the man, but in terms of representing how close he is to you I would think its closer to being normal. Or maybe I'm just thinking about this in the wrong way.