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Is it ok to replace the 50mm with a 35mm as your normal lens?


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#1 Adam Paul

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Posted 07 December 2005 - 01:21 PM

I know 50mm is supposed to be the "normal" lens in 35mm photography, but I always found it so narrow, specially when filming indoors. Is it ok to replace it with a 35mm? Will it impact the cinematography or the audience's perception of "normal" shot in anyway? I don't think a 35mm has the characteristics and distortions of a wide angle like a 24mm or even the 28mm, so I think it wouldn't be bad to use it as the normal lens. Reason I ask is because I want to buy a set of three 35mm motion picture primes and I was thinking of a 18mm, a 75mm and something in the middle. But the 50mm is to close to 75 and is too narrow for indoors. So I thought of a 35mm, making my set 18mm, 35mm, 75mm. I thought of 18mm, 35mm and 100mm as I prefer it to 75mm for close ups. But 100mm are almost always slower.
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#2 Adam Frisch FSF

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Posted 07 December 2005 - 01:28 PM

Of course. If you prefer it, then that's it. You don't need someone's permission and you won't be arrested by ASC's secret Hollywood SWAT team if you break the rules...
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#3 David Mullen ASC

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Posted 07 December 2005 - 01:32 PM

You can do whatever you want to do!

Actually, a 35mm lens is closer to "normal" perspective in the 4-perf 35mm movie frame, whereas the 50mm is closer for the 8-perf horizontal still camera frame, hence the confusion. So you're right, the 50mm looks a little longish. Maybe a 40mm would be the closest, I don't know -- I don't really care actually, I use whatever lens gets me the look I want.

Although because humans have peripheral vision, the most "natural" perspective comes from using the 50mm anamorphic lens for 2.35 photography because then you have a 50mm vertical perspective but see twice as much horizontally, more like a 25mm lens would.

It's a tough call -- some people would pick a 25mm, 50mm, 75mm as their three lenses, some an 18mm, 35mm, 75mm, etc. Truth is that three lenses doesn't really cover enough options, hence why most sets have five (18mm, 25mm, 35mm, 50mm, 75mm for example.)

A 50mm lens is really useful for over-the-shoulders, medium close shots, etc. It also tends to focus closer than some other primes.

I'd get a 75mm over a 100mm if I had to choose, unless I was adopting a long-lens style, in which case I'd drop the 18mm, which looks pretty wide-angle. I usually either use a 25mm for wide-angle shots, or the 20mm end of the zoom (if it's a 20-100mm). But again, it depends on the style and 35mm format, etc. If I were shooting in Super-35 and cropping to 2.35, I'd probably use slightly wider-angle lenses than for a 1.85 movie.

Edited by David Mullen, 07 December 2005 - 01:33 PM.

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#4 Max Jacoby

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Posted 07 December 2005 - 01:44 PM

Shooting a ratio that is wider than 1.33 means that you 'letterbox' your neg, so you reduce the vertical angle that your lens covers. So if one defines the 'normalcy' of a lens by the vertical angle that it covers, rather than the horizontal one (which make sense, since in most cinemas the height of the screen stays the same and the width changes to accomodate for different aspect ratios), then each aspect ratio has its own 'normal' lenght. So if one considers that the 50mm is the 'normal' lens for 1.33, then the 35mm will give you the same vertical angle if you shoot 1.66 and the 32mm if you shoot 1.85, which are all around 21 degrees.
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#5 Keith Mottram

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Posted 07 December 2005 - 02:25 PM

Shooting a ratio that is wider than 1.33 means that you 'letterbox' your neg, so you reduce the vertical angle that your lens covers. So if one defines the 'normalcy' of a lens by the vertical angle that it covers, rather than the horizontal one (which make sense, since in most cinemas the height of the screen stays the same and the width changes to accomodate for different aspect ratios), then each aspect ratio has its own 'normal' lenght. So if one considers that the 50mm is the 'normal' lens for 1.33, then the 35mm will give you the same vertical angle if you shoot 1.66 and the 32mm if you shoot 1.85, which are all around 21 degrees.


Max,

What about S35 and Anamorphic?

Cheers,

Keith
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#6 Laurent Andrieux

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Posted 07 December 2005 - 04:55 PM

The so-called "normal" focal length is something that can be discussed a lot, and some of the previous posts have been giving very interesting elements about that.

Some directors like the 35 mm or even the 32 mm (Bresson, Rhomer) as a "normal" focal length.

As it's been said, it's up to you to choose whatever lens you like as a "normal" one...

But if you see things a bit differently, you will see that it's not even worth putting forward this question.

I consider that the first parameter that one has to define for a shot is the point of view. It's the point of view that gives the perpective sight on a scene, not the focal length.

It's not difficult to prove this : the feeling of distorsion is not caused by short focal length but because of short distances of view. A long focal length only enlarges a part of the image one would get with a short lens, like using a magnifying glass, no more. It's common to consider short lenses give distorsion, but it's not true to think a short focal lens by itself does. Some "cheap" short lenses do, but it's not because of their focal length, but because of their building. Take a good lens, a view of a landscape with a short lens won't be distorded. Of course, short lenses are more commonly used at short distance, and therefore give a "distorsion" feeling (due to the distance, not the foccal length) and that telephoto lenses give the feeling of smashed perspective, but this is due to long distance, not long focal length.

The point of view gives you the relative distance you want to observe a scene at.

Then, you feel like showing a part of the scene, from this point of view.

One has to consider a focal length is only a viewing angle (at a given format). So what sense does a "normal" lens have, therefore ? The one that gives a viewing angle close to the human's eye ?... OK, but the human's eye is more like a variable angle lens system... Somehow, we sort of zoom when we look at things, with our brains, better than with our eyes only, just like we select sounds when we listen, what an ominidirection mic doens't do. This is why we do allow different sounds or voices at a same time but select the one we want to hear, what a recording system can't do, and then gives something "unearingable" when different people talk at the same time.

I think it's much more important you to determine the point of view, the viewing distance, and therefore, the focal lenght will very easily fall : it's the one that gives you the viewing angle you want... That's all !

And if you can't put your camera there, well, you'll have to cheat, and other lenses will help too...
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#7 Max Jacoby

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Posted 07 December 2005 - 06:24 PM

In Super35 a 27 or 28mm gives you the same angle, while in anamorphic it is the 50mm.
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#8 Adam Frisch FSF

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Posted 07 December 2005 - 07:00 PM

As usual, the general rule is that twice the diagonal of the frame in mm is the "normal lens". Therefore S35 framed for 2.40:1 needs a slightly shorter lens than if you'd use the full neg. In theory. This is all very anal and hair-splitting, but nevertheless.
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#9 Paul Bruening

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Posted 08 December 2005 - 04:29 AM

This was worked out in the early part of the century. The reason the industry selcted 50mm is due to some of the factors already mentioned. Distortion, linear perspective and distance compression are high on the list. Certainly, practicality is important as well. If you need the 35mm lens to squeeze into tight shoots then it's a good lens for you. But that 50mm will serve you in plenty of situations and serve you well. It is still the established standard for "normal".
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#10 Michael Maier

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Posted 08 December 2005 - 04:49 AM

I always thought 50mm was normal for 35mm still photography, not motion picture, where the frame is smaller.
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#11 Stepan Benda

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Posted 08 December 2005 - 11:15 AM

As usual, the general rule is that twice the diagonal of the frame in mm is the "normal lens". Therefore S35 framed for 2.40:1 needs a slightly shorter lens than if you'd use the full neg. In theory. This is all very anal and hair-splitting, but nevertheless.


I am sorry but it is not true! It would prpose to speak not about "normal" but "standard" lens. The definition of a "standard" lens would be: the "length" of the "standard" lens ( focusdistance) is approximately equal to the diagonal of the frame (not twice), because in that case would be the angle approx. 53 grades, which is the "standard" so to speak.

Stepan
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#12 Sam Wells

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Posted 08 December 2005 - 11:26 AM

I like the way you put that, Laurent.

-Sam
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#13 Adam Frisch FSF

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Posted 08 December 2005 - 02:25 PM

I am sorry but it is not true! It would prpose to speak not about "normal" but "standard" lens. The definition of a "standard" lens would be: the "length" of the "standard" lens ( focusdistance) is approximately equal to the diagonal of the frame (not twice), because in that case would be the angle approx. 53 grades, which is the "standard" so to speak.

Stepan


Hi.
Maybe I'm misunderstanding you, but you say that it shouldn't be twice the diagonal. In that case a "normal" 35mm lens would be around 25-28mm, which in my book is a rather wide lens. So I wouldn't agree there. But I would agree that twice the diagonal is little bit to long for my taste, but that's the rule I was tought.

At the end of the day one can argue about this until the cows come home - there are no set standards and the lines are blurred. For me a normal lens, meaning it's not wide, nor a telephoto, is somewhere between 30mm to 60mm. But this is just my personal view, of course.
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#14 Laurent Andrieux

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Posted 08 December 2005 - 04:47 PM

About once or twice the diagional distance :

It's been proposed that the good distance to observe a screen, considering the eye's viewing angle (but in fact we don't see things as a rectangle, did you notice ?) is the diagonal of the screen. Therefore, the "normal" focal length would be the diagonal of the format. But it only works if you look atthe screen from this distance.

It's obvious that mostof the people look at a longer distance from the screen, so there is a consensus on twice the diagonal.

If you consider 27 mm is the diagonal of the 35 mm image, twice the diagonal gives you a 54 mm. It's often considered that a wider lens is used. I actually teach my students to sit at once and half the diagonal. They should be at the good place if the director considered 40 mm is the "normal" lens, wich, I think, the most common. ( Do you have a 40 mm in your lens box ? More often we have a 35 and a 50...).

But the theater is bigger than that... If you remember that a "normal" focal length only gives you the respected perspective if you sit at the given distance - whatever lens and distance you consider as "normal"- you then realize how relative and poor meaning is this so-called "normal lens"...

I think cinema doesn't like "normal" things in general, by the way... neither do I...

And Sam, thanks ! :) I often think about what might people think of what I write here sometimes...It's true I am not often writing "normal" things either, am I ? I sometimes wonder if my english is not a problem, since I sometimes don't get any comment but from your reply, it sounds like it's not my english, is it ? ;) :rolleyes:
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#15 Leo Anthony Vale

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Posted 08 December 2005 - 05:35 PM

I am sorry but it is not true! It would prpose to speak not about "normal" but "standard" lens. The definition of a "standard" lens would be: the "length" of the "standard" lens ( focusdistance) is approximately equal to the diagonal of the frame (not twice), because in that case would be the angle approx. 53 grades, which is the "standard" so to speak.

Stepan


A standard lens having a focal length equal to the diagonal is a rule of thumb in still photography.

I've seen books on amateur movies from the 30s state thate one should film with a one inch lens in 16mm, project with a two inch lens and view from halfway between screen and projector so that one's viewing perspective matches the taking perspective.

I've also come across recomendations that the proper viewing distance for a photo enlargement is the diagonal of the print.

So the definition of normal/standard lens is based on perspective not angle of view.

---LV
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#16 Laurent Andrieux

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Posted 08 December 2005 - 06:23 PM

So the definition of normal/standard lens is based on perspective not angle of view.


They are linked...

the idea is to get the same angle of view as the lens has, as to get the proper perspective.

Mind that if you consider a small screen seen from far, the angle of view that gives you the proper perspective is much tighter (therefore the normal focal length will be much longer) while a big screen seen from close means a wide angle...

Since television definition is based on a 4.5 X the diagonal observation distance, the "normal " angle of view for a tv program is tighter than for a wide screen one (the focal length also depends on the image size...)

Also remind that screens size have enlarge a lot within a century (about 10 X..). As we get bigger TV screens, we should consider to shorten the focal length we use as "normal" on a TV production...
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#17 Paul Bruening

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Posted 09 December 2005 - 08:03 PM

Hey good folks,

I'll probably cause some irritation among my fellows without intending. We certainly all have our rules of thumb about lenses. I was taught one inch for 16mm and two inch for 35mm. This is from an old-school teacher.

The terms, "normal" and "standard" actually have to do with replicating how the human eye sees. There are quite a few optical and asthetic considerations that go into this replication. While all of the factors are not precisely as the eye sees, the factors, averaged together yeild a lens length for 35mm film of 50mm.

This size is still only approximate as variations in lens designs will tend to favor some optical factors over others.

Why did the movie industry obsess about the "normalicy" of a lens? Suspension of disbelief. A normal lens has a greater capacity to lull the viewer into forgetting that they are watching a movie.

Longer lenses where needed for facial close-ups since a normal lens will tend to elongate facial features when used that close to a face. Again, the issue was a matter of replicating, to the best factors of optics what the eye sees.

There are very good reasons to respect the knowledge and experience of those extremely capable people that came before us in the industry.
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