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class="Paragraph" style="margin-bottom: 0">50mm Lens On S16mm & 35mm

Published : 12th May 2004

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Jeff Kreines wrote :

re - the 16mm and 35mm lens kafuffle...

class="Paragraph" /Super1635mmLenses.htm

>Perhaps he meant to say something slightly different, like "a 25mm lens is 'normal' (whatever 'normal' means) on a 16mm camera, and a wide angle on a 35mm camera?

> But the focal length remains the same -- 50mm = 50mm.

A "standard" or "normal" lens is the lens that gives the field of view approximate to the field of view of the naked singular ( ie close the other one stupid..) Mk I human eyeball. Back in the past as a trainee stills photographer I was taught that the diagonal of the neg area will give you the size of the standard lens. For a 35mm stills camera the diagonal is 50mm and like magic there is the answer. Walk up to a 120 roll film camera, different answer.

Got a set 35mm (so called because they cover the neg area of the camera system only) lenses that you wish to use on a S16 camera? Or even a Video camera with a PL mount? No problem. Measure the diagonal to find the "standard".

Now for the fun bit. The "Standard" lens will change every time the actual neg area changes. The actual neg area changes every time you change the ground glass but it only matters in the extremes. Matching shots from a standard 35 and Super 35 may not pose any problems but remember when you did that 2 perf 2.35:1 shoot last year their never seemed to be a lens quite wide enough for the job in the box.

As for anamorphic lenses? Please don't ask. That is rocket science.

Cheers
Andrew Horton
Poverty stricken Camera Assistant
- If I was a rocket scientist I would be rich by now-
Sydney Australia



>For a 35mm stills camera the diagonal is 50mm and like magic there is the answer. Walk up to a 120 roll film camera, different answer.

A 35mm still camera covers twice the area of a 35mm movie frame.

What's the diameter there?

Robert Rouveroy csc
The Hague, Holland

I plan to live forever. So far, so good.



I haven't been following this thread closely but:

>For a 35mm stills camera the diagonal is 50mm

No it is 43.267mm

The diagonal is the square of both sides added together and then find the square root of this sum

For example :

24mm x 18mm (Full Aperture?)
24x24 + 18x18 = 576 + 324 = 900
…The square root of 900 is 30
…The diagonal is 30mm

Cya

Steve Morton

Scientific Imaging
Monash University
Melbourne
Australia



Steven Morton wrote :

>The diagonal is the square of both sides added together and then find the square root of this sum

Freaky. I've just been 'helping' my stepson with his homework and this is exactly the formula I couldn't remember!

'SOH', 'CAH', 'TOA' etc, etc, - I'm sure I wasn't alone in staring out of a sunny classroom window thinking, "I'll never need to know THIS bullsh*t when I leave school".

Tom Townend
Cinematographer/London



Andrew Horton writes :

>A "standard" or "normal" lens is the lens that gives the field of view approximate to the field of view of the naked singular ( ie close the other one stupid..) Mk I human eyeball.

I was taught that, too. But it's not true. The field of view of the human eye is damn near 180 degrees wide. What they actually meant was the field of view represented by a framing rectangle of arbitrary size at an arbitrary distance from the human eye...which, of course, is meaningless. In other words, a "normal" focal length is arbitrary.

>I was taught that the diagonal of the neg area will give you the size of the standard lens. For a 35mm stills camera the diagonal is 50mm

Not exactly, but let's assume it is. Why, then is 50mm also considered "normal" for 35mm motion picture frames, which are considerably smaller than stills frames?

What's "normal" is usually a matter of consensus.. There's a ballpark within which you'll get minimal distortion or compression, and which works for most photographic purposes. With stills, anything from about 42mm to 55mm can be considered "normal."

"Portrait" lenses start at about 75mm and "wide angles" at 35 to 38mm.

Dan "and then there are zooms..." Drasin
Producer/Lenser
Marin County, CA



Tom Townend writes :

>'SOH', 'CAH', 'TOA'

The math tutor my despairing parents hired taught me the trig functions as SOPPY CADJY TOAD. For some weird reason that got me back on the rails.

Dan Drasin
Producer/DP/Rocket Scientist (in my next lifetime)
Marin County, CA



>So to sum up, lenses are the same whether they’re fitted to a 16mm or 35 mm camera. 14mm is still a 14mm, no matter if there is more glass in a larger barrel to suit the size of camera.

You've got it. It is surprising how many people don't get this because the angle of view varies from film size to film size (and chip size too) Anyone who is looking at digital still cameras these days finds the same thing - they list the focal length of the lens and then tell you what the 35mm[still] equivalent focal length would be...equivalent meaning "having the same angle of view."

Mark Weingartner
LA based



>Actually, 32mm is considered "normal" for 35mm motion photography.

I always thought that 50mm was considered "normal" for 35mm still camera, 35mm for 35mm Academy and 25mm was "normal" for standard 16mm. Is that true?

Robert Rouveroy csc
The Hague, Holland



In reply to :

>Actually, 32mm is considered "normal" for 35mm motion photography.

Mitch gross writes :

>This gets so silly. Would that be 35mm 1.33 academy? How about silent? Did it change with 1.85? Is it different for 1.66? And then there's Super-35

It is silly. FWIW, 32mm was considered to be the focal length that most closely duplicated the human field of view. And it was for the Academy format.

For standard 16mm it was a 16mm lens. Other formats changed proportionally.

I can't remember who made this determination.

Brian Heller
IA 600 DP



Robert Rouveroy writes :

>I always thought that 50mm was considered "normal" for 35mm still camera, 35mm for 35mm Academy and 25mm was "normal" for standard 16mm. Is that true?

Yes, it is. And AFAIK, it still is.

Brian Heller
IA 600 DP



>I always thought that 50mm was considered "normal" for 35mm still camera, 35mm for 35mm Academy and 25mm was "normal" for standard 16mm. Is that true?

It's an artificial concept - human vision is a little too complicated to be reduced to a single number. Our field of view (when including our peripheral vision) is close to 180 deg.

Jessica Gallant
Los Angeles based Director of Photography
West Coast Systems Administrator, Cinematography Mailing List
http://www.cinematography.net



Brian Heller a ecrit :

>It is silly. FWIW, 32mm was considered to be the focal length that most closely duplicated the human field of view. And it was for the Academy format. For standard 16mm it was a 16mm lens. Other formats changed proportionally. I can't remember who made this determination.

>Robert Rouveroy writes :

>I always thought that 50mm was considered "normal" for 35mm still camera, 35mm for 35mm Academy and 25mm was "normal" for standard 16mm. Is that true?

>Yes, it is. And AFAIK, it still is. Brian Heller

Now I'm thoroughly confused. Are you twins?

Robert Rouveroy csc
The Hague, Holland



This must be the third go-round for all this on CML.

There's "normal" angle of view for monocular vision, "normal" angle of view for binocular vision; then there's peripheral vision....

You could say that 25mm in 16mm format is "normal" in terms of perspective, but the field of view at that focal length is limited given the above.....

How'd that Martin Mull song go ?

"It don't have to be that formal, honey let's you and me get normal for a change"

Sam Wells



Sam Wells writes :

> This must be the third go-round for all this on CML.

That's never stopped us before.

>There's "normal" angle of view for monocular vision, "normal" angle of view for binocular vision; then there's peripheral vision....

Yes, and some people have more peripheral vision than others.

>You could say that 25mm in 16mm format is "normal" in terms of perspective, but the field of view at that focal length is limited given the above.....

The only thing normal about 25mm on16 and 50mm on 35 is those are the lenses that cameras "normally" come with when they're purchased. Somebody probably at Kodak did some kind of research and determined that 50mm would be the best general purpose focal length for most people. I seem to remember someone from Nikon saying that they made 10 times more 50mm lenses than any other focal length. It may actually have been a higher number.

The focal length that most nearly approximates the human field of view is 32mm on 35. This does not include peripheral vision or turning one's head as in Cinerama; or 360 degree vision as demonstrated by Linda Blair in "The Exorcist". But most vision experts agree that is not normal.

Brian Heller
IA 600 DP



Dan "and then there are zooms..." Drasin wrote :

>...I was taught that, too. But it's not true. The field of view of the human eye is damn near 180 degrees wide. What they actually meant was the field of view represented by a framing rectangle of arbitrary size at an arbitrary distance from the human eye....which, of course, is meaningless. In other words, a "normal" focal length is arbitrary...

Okay, students, listen up. I haven't been following this thread, and I see it's going haywire.

The "normal" lens is not a purely arbitrary matter. It does actually relate to human vision. As you know, we have sharp vision only in the area of the retina in and around the fovea. When we want to see detail we swivel our eyeballs and/or turn our heads to centre the desired object in that area of the retina. Everything else has greatly diminished resolution. The Creator gave us a very neat vision system, one that allows excellent resolution where we need it, but just vague representations elsewhere in the visual field. This permits us to concentrate without excessive distraction by off centred subjects, while still giving us warning of incoming dangers and a good feel for where we are spatially.

Because of this limited sharp visual angle, we tend to view objects at different distances, depending upon the size of the subject. We might view a breadbox at 3 feet, but we'll back off to 30 feet or so to view an automobile. We do this when we want to see the object overall, to be able to size up its proportions. You can view the auto at 6' and get it all into that 170 degree angle your eyes possess, but you can't really size up its proportions from there. Same reason a painter moves close to the canvas to paint some detail, then backs off 5 feet or so to see what it looks like, i.e., to see how it all fits together.

The normal lens for any format is the lens that forces you to shoot from approximately the distance you would choose to comfortably view that object overall with your eyes. That's why the "normal lens" is commonly defined as the focal length that produces the same perspective as the eye. Perspective is determined by viewing/shooting distance, so the perspective of an object will look the same in the normal lens photo as it does to the eye, viewing it comfortably. (By comfortably, I mean at a distance that allows you to see the whole object relatively sharp and size up its proportions without a lot of eye/head movement.) It happens that, because of the size of the foveal area, a focal length equal to the diagonal of the format produces that angle of view.

The story doesn't end there. The only way the resulting photograph will still appear to have the same perspective the eye saw is if the final print is viewed at the correct viewing distance. This distance will have to be proportionate to the focal length that shot it, so if the print was produced by blowing up the neg. 2X, then the correct viewing distance will be the lens focal length X 2. Viewed at this distance the perspective in the scene will look natural, not distorted, foreshortened, or flattened. But with photos we can view at any distance we wish, something we can't do with the naked eye. So if we view that photo too far away the perspective looks foreshortened--the "wide angle" look. If we view it too close, the perspective in it looks flattened--the "telephoto" look.

And of course, we like to use that technique. We know that the viewer will look at all pictures of a similar size at the same distance, so having shot them with different focal lengths, the viewer will experience variations in perspective he can't see naturally. The viewer will look at all 8x10 prints at the same distance, about a foot away, because that's the distance that allows him to see the whole print easily--back to the comfortable viewing angle idea again. Blow it up to 16x20 and he will back off further to view it comfortably overall. If the original neg. was 4x5 and it was shot with the normal lens for 4x5 (6.4 inches, or 163mm) the correct viewing distance for a full frame blowup to 8x10 is 2 x 6.4 inches, about 13 inches. That will give him a natural looking perspective of the subjects in that photo. Blow it up to 16x20 and the correct viewing distance is 26 inches, etc.

When the Leica camera came out it was equipped with a 50mm lens, a focal length that had been popular for some time in film work on 35mm film. (The Leica evolved out of a camera that had been constructed for the purpose of making exposure tests on 35mm mp film and used a common mp lens.) Of course, the Leica’ s still format (24mm x 36mm) was twice that of the movie format, so why was 50mm being used for filming? Kodak, preparing to offer a new 16mm format for home movies in the early 20's, analysed this question, because they were going to make a new camera in a new format and it would come with one lens : what focal length should be used?

Here are a couple of their considerations :

When viewing films the average viewer sat about half way between projector and screen. For common screens of that day (and ever since, in 1:33) the average viewer was about twice the correct viewing distance for the screen size, so using the still camera formula for normal lenses would make perspective in the scenes appear foreshortened. Double that focal length looked more natural to most viewers. (Another consideration was that since the user would be filming action subjects, there needed to be more working distance between camera and subjects than needed for stills.) Thus, it was established that for motion picture cameras, the normal lens should be a focal length equal to twice the diagonal of the format. For 16mm, that is 2 X 12-1/2mm, or 25mm. For 35mm full aperture, 31mm.

As other manufacturers got in on the Leica craze they followed suit with the 50mm lens on their competing cameras. But the true diagonal is 43mm.

When it comes to wide screen formats....I don't know any data on this, relative to viewing distances and focal lengths for the plethora of formats now extant. If anyone else does, please chime in!

It's little wonder that there has always been so much confusion about the normal lens. I've yet to see this all explained in any text. I figured it out by studying bits and pieces of info over several years until it all gelled.

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614



WKR wrote:

>...Thus, it was established that for motion picture cameras, the normal lens should be a focal length equal to twice the diagonal of the format. For 16mm, that is 2 X 12-1/2mm, or 25mm. For 35mm full aperture, 31mm...

Oops! For 35mm full aperture it is 31mm x 2, or 62mm. 31mm is the diagonal of the full aperture.

Sorry about that!

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614



>Our field of view (when including our peripheral vision) is close to 180 deg.

I saw a " 60 Minutes" (CBS) episode years ago, shot in a hospital in Russia, in a hospital that took in the people from a village that was subjected to nuclear fallout from nearby explosions/tests-purposely- Doctors were instructed not to treat these patients, but merely observe and write down the data. Most of the young men ended up in a cemetery shortly thereafter, and the women gave birth to deformed babies-young men were born without a left arm, and the most bizarre recollection - I think they showed a foetus in a jar born with one eye( Cyclops)

Did anyone else see this? It's been a few years since it aired…

John Babl
Miami



All of these issues regarding "normal" is why I think the 40mm or 50mm anamorphic lens is perhaps closest to human vision in that the vertical perspective is like a 40mm or 50mm spherical -- but it has twice the horizontal field of view.

Of course, viewing distance is another factor. IMAX movies often use very wide-angle lenses but most of the image falls into our peripheral vision unless we sit in the back of the theatre -- so we are in essence only concentrating on a "longer focal length" view in the (lower) centre of the frame. Cinerama had a similar effect in that the image was pretty wide-angle (three 27mm lenses on three 6-perf 35mm frames for a total field of view of 146 degrees) but we tended to look at the centre of a very large theatre screen and let the sides engage our peripheral vision.

David Mullen
Cinematographer / L.A.



Robert Rouveroy writes :

>Now I'm thoroughly confused. Are you twins?

Who wants to know? RR1, RR2 or RR3?

Brian "I stand by whatever I said" Heller
IA 600 DP



Quoth Wade :

>Okay, students, listen up. I haven't been following this thread, and I see it's going haywire...

Thanks, teach...

The first time I stood in front of some very wide lens stills with my nose touching the glass to test the premise that viewing from the right place would undistort the perspective, I was amused and amazed to see how well it worked.

Wade's description and explanation of all this is concise and easy to follow - and I would ask for permission to print up copies to give to directors who don't get it, but I am afraid that after reading this, they would still not get it but would quote bits back to me to prove that they had...so I will just print a copy for myself:

Mark Weingartner
LA



Wade Ramsey wrote:

>Okay, students, listen up. I haven't been following this thread, and I see it's going haywire.

That's the best explanation I've ever read in chasing down the source of the ever elusive normal lens.

I'm going to take Mark Weingartner's route and print it out for myself.

I'll refer the directors directly to Wade.

Brian "More normal now" Heller
IA 600



Mark Weingartner wrote :

>...so I will just print a copy for myself:

Feel free! You aren't going to find it anywhere else, so far as I've found. So if it's helpful use it!

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614



Been away for a while (quite a while) but am back.

I remember bugging everyone about the normal lens a couple of years ago. The thread was never ending with lots of opinions until Mr. Ramsey's excellent answer that cleared it up for me.

Mr. Ramsey thou art truly a patient man .

Manu"deja vu"Anand
New Delhi



>A "standard" or "normal" lens is the lens that gives the field of view approximate to the field of view of the naked singular ( ie close the other one stupid..) Mk I human eyeball.

O.k., so my question is - what lens do most folks use when simulating a POV.

I had always heard (in my very informal education) that 50mm was "normal" for 35mm motion picture work. I'm reading here that 32mm is actually considered normal and this makes much more sense to me.

For instance, if I'm doing a handheld walk through a location to simulate someone's walking POV, I'll use anything from a 32mm to a 24mm - and more often the wider.

Roderick Stevens
Az. D.P. (I see in wide angle)
www.restevens.com
12on12off



>I had always heard (in my very informal education) that 50mm was "normal" for 35mm motion picture work. I'm reading here that 32mm is actually considered normal and this makes much more sense to me.

I suspect 50mm is "normal" perspective and 32mm is "normal" angle of view.

Art Adams, DP [film|hdtv|sdtv]
Mountain View, California - "Silicon Valley"
http://www.artadams.net/