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16mm or 35 mm lenses


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#1 Martin Amezaga

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Posted 02 January 2008 - 11:53 PM

Hi, I'm going to make a short film on 16mm. I know that when shooting on 16 mm any lense focal distance is equivalent to half its focal distance when used on 35mm. For example a 25 mm lesne used on 16mm is the same as a 50mm used on 35mm .
If that is correct, what happens with the sense of space.

For example:

A lense with a focal distance of 25mm used on 16mm camera will have exactly the same feel as a 50mm focal distance lense used on 35 mm film?

If there are any, what are the differences and how can I work with them?

Is it better to use 35 mm lenses than 16 mm lenses when working on 16mm film cameras?

Hope I made my self clear enough. Thanks in advance, best regards.
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#2 Michael Nash

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Posted 03 January 2008 - 01:06 AM

The focal length of a lens does not change between 16mm and 35mm formats, only the angle of view changes. A 50mm lens is a 50mm lens no matter what camera format it's on, so you can't use "35mm lenses" instead on a 16mm camera, because they're the same lenses. Think of it this way -- the lenses, and the camera to an extent, are the same no matter what film is running through it. Since 16mm film is half as wide as 35mm film, it can only capture half the width of the image that 35mm film can capture from that lens.

Depth of field changes with focal length. A 25mm lens will have more depth of field than a 50mm lens, when using the same f-stop and distance to subject.

"Sense of space" is created by many visual cues, such as depth of field, linear perpective, planes of focus, camera movement, contrast, color, atmospheric haze, and so on. With smaller gauge film and video formats that use short focal length lenses it can be difficult to get a shallow depth of field to create visual depth and separation, so you use other visual cues to create the illusion of depth.
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#3 Jonathan Bowerbank

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Posted 03 January 2008 - 01:45 AM

The focal length of a lens does not change between 16mm and 35mm formats, only the angle of view changes.


Just so Martin knows, "Angle of View" can also be called "Field of View"
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#4 Tim O'Connor

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Posted 06 January 2008 - 10:47 PM

The focal length of a lens does not change between 16mm and 35mm formats, only the angle of view changes. A 50mm lens is a 50mm lens no matter what camera format it's on, so you can't use "35mm lenses" instead on a 16mm camera, because they're the same lenses. Think of it this way -- the lenses, and the camera to an extent, are the same no matter what film is running through it. Since 16mm film is half as wide as 35mm film, it can only capture half the width of the image that 35mm film can capture from that lens.

Depth of field changes with focal length. A 25mm lens will have more depth of field than a 50mm lens, when using the same f-stop and distance to subject.

"Sense of space" is created by many visual cues, such as depth of field, linear perpective, planes of focus, camera movement, contrast, color, atmospheric haze, and so on. With smaller gauge film and video formats that use short focal length lenses it can be difficult to get a shallow depth of field to create visual depth and separation, so you use other visual cues to create the illusion of depth.


Veni, vidi, vici. I'm not there yet but I don't know if there's a Latin phrase for "I've come to understand,
I'm going to understand, I understand". Anyway, I'm not quite ready to say that I understand.

An Xmm lens is an Xmm lens is an Xmm lens. I'm getting with the program.

Now my local camera rental house
has in its catalogue separate sections for 16mm (format) lenses and 35mm (format) lenses.

When somebody shoots a Super 16 project and rents a more expensive lens package from
the 35mm format options, what are they gaining? Superior optics? Faster speed?

With the 35mm format lenses, does the person shooting Super 16 simply adjust so that if a shot
is desired with the angle of view that would ordinarily be obtained with a 25mm lens designed for
16mm cameras, a 50mm lens designed for 35mm images is used? (if this is done, does the Super 16
filmmaker get the desired frame but a different depth of field because a different focal length lens
is used to get that same angle of view onto the 16mm image?)

I know this seems to contradict "the same lens" argument. I'm afraid that I can almost hear you bashing
your head against the wall.

I guess that I haven't had to wrestle with this because I've shot 16mm with zooms or primes designed
for 16mm images of 35mm with lenses designed for 35mm images or video with zooms and then never
really though too much in terms of numbers but rather wider or tighter.

Now that the issue is coming up for me of using lenses that are traditionally used for larger image formats
for smaller formats, I'm finding that although NASA and JPL do indeed consult me for problems with
telescope lens intended for seeing far into the universe, I am somehow struggling with these equations.

I know that these questions must be about as much fun as Gee how can I make video look like film but
somehow I get hung up on them. Thanks for your patience.

Please don't tell NASA, JPL or the agent that represents me for my freelance scientist work. I need the
money.
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#5 Chris Keth

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Posted 06 January 2008 - 11:33 PM

See this post: http://www.cinematog...mp;#entry212029 as well as the post I just made at the end of it.
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#6 Chris Keth

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Posted 06 January 2008 - 11:42 PM

1.:When somebody shoots a Super 16 project and rents a more expensive lens package from
the 35mm format options, what are they gaining? Superior optics? Faster speed?

With the 35mm format lenses, does the person shooting Super 16 simply adjust so that if a shot
is desired with the angle of view that would ordinarily be obtained with a 25mm lens designed for
16mm cameras, a 50mm lens designed for 35mm images is used? (if this is done, does the Super 16
filmmaker get the desired frame but a different depth of field because a different focal length lens
is used to get that same angle of view onto the 16mm image?)


By using 35mm format lenses on 16mm film, you don't really gain a thing. Perhaps superior optics since generally 35mm is better supported. Perhaps you might gain familiarity with a particular series of lense you favor.

Repeat "A 50mm lens is a 50mm lens" a million times. If you were to rent a 50mm lens designed for 16mm film, a 50mm lens designed for 35mm film, and a 50mm lens designed for 4x5 inch film and try them all out, you would see absolutely zero difference in field of view, the apparent "wideness" or "telephoto-ness" of the lens, or depth of field assuming each lens was shot at the same stop.

Additionally, imagine a test where you have an identical 50mm lens on a 16mm camera and on a 35mm camera. Each lens is focused on a tape measure laid out on the floor and sharp focus is placed on a point 6 feet from each film plane. even though the field of view would be different, you would find that the depth of field would be exactly the same.
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#7 David Mullen ASC

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Posted 06 January 2008 - 11:48 PM

With the 35mm format lenses, does the person shooting Super 16 simply adjust so that if a shot
is desired with the angle of view that would ordinarily be obtained with a 25mm lens designed for
16mm cameras, a 50mm lens designed for 35mm images is used? (if this is done, does the Super 16
filmmaker get the desired frame but a different depth of field because a different focal length lens
is used to get that same angle of view onto the 16mm image?)


Yes -- just to keep it simple, if you cut the focal length in half to maintain the same field of view, you effectively gain two stops more depth of field (which you could compensate for by opening up by two stops.) Hence the value of using the new Ultra-16 Zeiss T/1.3 lenses -- you can shoot with them wide-open at decent quality and get a similar depth of field to when you shoot in 35mm at T/2.8. Unfortunately the old Zeiss Super-Speeds are rather soft at T/1.3.

Generally when you are shooting, you aren't mixing Super-16 and 35mm, so you just get used to the field of view of the lenses you have and you stop trying to transpose them in your head. You just know that your 25mm lens in Super-16 has a medium view, your 12mm is wide-angle, etc. You stop thinking "this 25mm is sort of like a 50mm lens on a 35mm camera..."
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#8 Tim O'Connor

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Posted 07 January 2008 - 01:52 AM

Thanks guys, I'm really getting it. Lately I've come across several people doing Super 16 projects
and I've heard so many comments in different directions about their lens packages...!

It's about time I went through my ASC manual like I do periodically so that's a good suggestion Chris
to look at the charts.

Incidentally, I used to carry it and also my Spectra with me and wherever I went, pizza places, ATMs,
pumping gas, anywhere, I'd measure footcandles.

I started to get good at estimating footcandles and I really enjoyed
being able to use the ASC chart for footcandles/ASA/stops with the footcandles that I found wherever I
metered. Then whenever I went any place without the manual and meter, I'd guess how many footcandles
there were and how I would expose depending on what stock I imagined using.


David, I knew that you were on "Big Love". It was the other David who posted in that thread who had been
in an episode of "24" last year.

Thanks again. If I ever ask another question that violates the " A 50mm lens is a 50mm lens is a 50mm lens"
mantra, I will pay enough of a fine to the forum to buy coffee for everybody who posted replies to the
first zillion times I asked.
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#9 robert duke

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Posted 07 January 2008 - 10:00 AM

Veni - I came.
Vidi - I saw
Vici - I conquered.
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#10 Sam Wells

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Posted 07 January 2008 - 11:47 AM

Veni - I came.
Vidi - I saw
Vici - I conquered.


Venti - I gave in and went to Starbucks

-Sam

p.s. Ansel Adams' "The Camera" is still I think the best introduction to basic geometry of lenses forming images.

But David and Chris have you on the right course.

-Sam
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#11 John Sprung

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Posted 07 January 2008 - 02:10 PM

If you were to rent a 50mm lens designed for 16mm film, a 50mm lens designed for 35mm film, and a 50mm lens designed for 4x5 inch film and try them all out, you would see absolutely zero difference in field of view, the apparent "wideness" or "telephoto-ness" of the lens, or depth of field assuming each lens was shot at the same stop.

All true, but there is a difference in design between these lenses: the size of the image they make.

Hang the 4x5 view camera lens on an Arri 16-S, and you'll get the same telephoto-ness that you'd get from a lens designed for that camera, but it wouldn't be as sharp, and you'd have to use the matte box to keep from having loads of extraneous light bouncing around in there. Adapt the Arri 16's lens to the 4x5 view camera, and it wouldn't cover the whole plate -- you'd get a very nice sharp image, but only in a fuzzy-edged circle in the middle. That's the main way in which lens designs are optimized for a particular film format.

This fact was a pain in the tush in the early days of Super-35, as there were lots of lenses designed for the Academy aperture that didn't quite cover the Super frame, or only covered adequately at deeper stops. Wide open, you'd get fuzzy darkening in the corners.

You can look at this directly using any lens and an ordinary sheet of paper. Take them into a room where you can have something bright at one end, like lamps or daylit windows, and go down to the other end of the room. Point the lens at the light, and hold the paper where the film plane should be. You'll see a circular image upside down. The bigger the format the lens was designed for, the bigger the image. It even works with an ordinary hand magnifying glass, or strong reading glasses.

Bottom line, too much lens is a little below the optimum, not enough lens just plain doesn't work.




-- J.S.
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#12 Bill DiPietra

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Posted 07 January 2008 - 04:03 PM

Veni - I came.
Vidi - I saw
Vici - I conquered.


Is that like Asa Nisi Masa in Fellini's "8 1/2?"...lol ;)
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#13 Peter Anderson

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Posted 07 January 2008 - 06:00 PM

Ok so let me get this completely straight...

a 50mm lens on 35mm format ISN'T the same as a 25mm lens on 16mm format because the shorter lens still suffers from increased distortion in perspective caused from having a shorter focal length? So if i wanted a similar sense of distance between formats I would have to sacrifice field of view?

Is that a correct assumption.

Desipte the hammering of posts its still a little confusing. If i like the look of a 50mm lens on a 35mm camera it seems that essentially I cannot replicate it exactly on 16mm, not without sacrificing some element of composition at least.
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#14 David Mullen ASC

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Posted 07 January 2008 - 06:18 PM

Ok so let me get this completely straight...

a 50mm lens on 35mm format ISN'T the same as a 25mm lens on 16mm format because the shorter lens still suffers from increased distortion in perspective caused from having a shorter focal length? So if i wanted a similar sense of distance between formats I would have to sacrifice field of view?

Is that a correct assumption.

Desipte the hammering of posts its still a little confusing. If i like the look of a 50mm lens on a 35mm camera it seems that essentially I cannot replicate it exactly on 16mm, not without sacrificing some element of composition at least.


You can match the composition. I think some are just saying that the shorter focal lengths could have some curvature on the sides, though a 25mm lens is not particularly short.

Perhaps when you start talking about using a 9mm on a Super-16 camera to match the look of a 18mm lens on a 35mm camera -- or even wider-angle shots -- that you may have to look harder for some good wide-angle lenses that don't have barrel distortion on the sides.

I think you're worrying too much over this.
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#15 John Sprung

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Posted 07 January 2008 - 06:26 PM

a 50mm lens on 35mm format ISN'T the same as a 25mm lens on 16mm format because the shorter lens still suffers from increased distortion in perspective caused from having a shorter focal length? So if i wanted a similar sense of distance between formats I would have to sacrifice field of view?

Perspective and field of view would be a very close match. The big difference would be Depth of Field at a given stop. You can get that closer by going a couple stops deeper on the larger format.

Another little secret: The focal lengths of prime lenses aren't necessarily high precision numbers. Something that's marked 50 mm could, if you measure precisely, be more like 48.6 or 51.8 or something like that. So, two different makes of 50 mm on the same camera may well give you slightly different fields of view. You'd have to noodge the dolly a little bit in or out to make better matching compositions.



-- J.S.
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#16 Peter Anderson

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Posted 09 January 2008 - 03:16 PM

I think you're worrying too much over this.


I think you're right :)
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