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35mm & s16 mm


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#1 Matias Nicolas

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Posted 24 April 2008 - 07:38 PM

I have this doubt, : why in s16 the set starts in 9.5 , 12 , 16 , 25 and 50 mm, and if you need a tele you have to use an 85 or 135 mm of 35mm... why the set of 35 mm, usually starts in 16, 24, 32, 50, 85 mm..? why in s16mm you have like more wide open lenses ... I dont understand that, cause if you put a 50 mm of s16 in a sr3, and then you put a 50 mm of 35 mm, you have the same image?
I have this doubt cause Im shooting a film, and the director always shoots in 35 mm, so he speaks of a 100 mm when we put a 50 mm of s16 in our sr3 ... if you have the same image... so then this doubt about the numbers occured, and nobody could answer it, in our camera crew !!! thanks..
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#2 Michael Nash

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Posted 24 April 2008 - 08:01 PM

I dont understand that, cause if you put a 50 mm of s16 in a sr3, and then you put a 50 mm of 35 mm, you have the same image?


No, you don't. The 16mm frame is half the width of the 35mm frame, so the same lens will give you a field of view that's half as wide. You need a 25mm lens in the 16mm format to give you the same field of view as a 50mm lens in the 35mm format.
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#3 Matias Nicolas

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Posted 26 April 2008 - 07:46 PM

try it, but it is not that way.... you ll have the same angle ... put a sr3 , put a 25 mm of 16mm, and then a 25 mm of 35mm, you will have the same angle of view..
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#4 Mike Rizos

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Posted 26 April 2008 - 08:24 PM

Matias this has been discussed once or twice previously.
http://www.cinematog...;hl=16mm lenses
http://www.cinematog...;hl=16mm lenses
http://www.cinematog...;hl=16mm lenses
http://www.cinematog...;hl=16mm lenses
http://www.cinematog...-16mmvs35mm.htm
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#5 Chris Keth

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Posted 26 April 2008 - 08:47 PM

try it, but it is not that way.... you ll have the same angle ... put a sr3 , put a 25 mm of 16mm, and then a 25 mm of 35mm, you will have the same angle of view..


No, you won't have the same field of view. Please don't ask a question and then argue with the answer. <_<

A 35mm lens has a particular field of view for the 35mm format. If you use that same lens on a 16mm camera, you are using only part of that projected light, so the field of view is narrower. Try it at a rental house. Set up a 16mm camera with a 50mm lens so that a chart is filling the frame. Set up a 35mm camera right next to it with a 50mm lens. The chart will not fill the frame of the 35mm camera.

Check out the links in the post above mine. We generally explain this topic in length about once a month.

Edited by Chris Keth, 26 April 2008 - 08:48 PM.

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#6 Michael Nash

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Posted 27 April 2008 - 12:41 AM

try it, but it is not that way.... you ll have the same angle ... put a sr3 , put a 25 mm of 16mm, and then a 25 mm of 35mm, you will have the same angle of view..


You're talking about two different things. A 25mm lens from a 16 set will have the same field of view as a 25mm lens from a 35 set (more or less; there are some manufacturing differences noted in those other threads). But A 25mm lens on a 35mm camera will have a field of view twice as wide as a 25mm lens on a 16mm camera. The focal length is the same, and projecting an image onto the film at the same distance. But since 16mm film is only half as wide as 35mm film, it can only "see" half as wide as the 35mm film.

Cover up half of the 35mm frame and you've got the size of the 16mm frame. If you cover half the frame, the field of view is half as wide.

screenshot2.jpeg
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#7 Tim O'Connor

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Posted 27 April 2008 - 11:22 AM

You're talking about two different things. A 25mm lens from a 16 set will have the same field of view as a 25mm lens from a 35 set (more or less; there are some manufacturing differences noted in those other threads). But A 25mm lens on a 35mm camera will have a field of view twice as wide as a 25mm lens on a 16mm camera. The focal length is the same, and projecting an image onto the film at the same distance. But since 16mm film is only half as wide as 35mm film, it can only "see" half as wide as the 35mm film.

Cover up half of the 35mm frame and you've got the size of the 16mm frame. If you cover half the frame, the field of view is half as wide.

screenshot2.jpeg



I know that people can tend to think of, and I've heard it expressed this way, a 50mm lens
as being "more telephoto" in 16mm than 35mm.

While that can be one way to approach the subject, your explanation and illustration show that the tighter field of view with the 50mm lens in
16mm is because that is the image area available and that's how much of it is covered with the 50mm lens.

I think that even if people continue to use this shorthand language that helps them go back and forth between formats and choose lenses
for close-ups, you've given an extremely clear explanation for why a lens may seem "more telephoto" and that is going to clarify for a lot of people why different focal length lenses in different formats are used for the same field of view and the corollary of why the same focal length lenses in different formats provide different fields of view.
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#8 Brad Grimmett

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Posted 29 April 2008 - 12:23 AM

I think he was comparing a 16mm 'format' lens with a 35mm 'format' lens, which would explain why the field of view was the same or similar.
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#9 Tim O'Connor

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Posted 29 April 2008 - 12:57 AM

No, you don't. The 16mm frame is half the width of the 35mm frame, so the same lens will give you a field of view that's half as wide. You need a 25mm lens in the 16mm format to give you the same field of view as a 50mm lens in the 35mm format.




Brad Grimmett Posted Today, 01:23 AM
I think he was comparing a 16mm 'format' lens with a 35mm 'format' lens, which would explain why the field of view was the same or similar.


Hi Brad. Yes, I think maybe I worded it poorly. I understood that but I like the way that Michael illustrated how a similar field of view from shooting in 35mm
or 16mm requires different focal lengths because of the different image areas.

I don't know; I tend to mangle my discussions on this topic but I found that picture very helpful. I guess because by seeing how the same focal length lens, used for shooting different film sizes, produces different fields of view; it helped me work my way backward into a new way of looking at how the different focal lengths produce the same or similar fields of view when shooting with different (16mm or 35mm) film sizes.

To all those of you who have discussed this with me before, I promise you that I remember and am repeating the mantra "A 50mm lens is a 50 mm lens is a 50mm lens." "A (focal length) is (a focal length) is a (focal length.)

I haven't forgotten; just haven't improved in talking about it. I'll stop now.
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#10 Matias Nicolas

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Posted 18 May 2008 - 07:05 AM

Thanks for the answers... now I understand... but now I have ahother doubt ...

If I use an 85 mm on a s16 camera, Its like a 170 mm, but I have the same depht of field, no?
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#11 Nate Downes

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Posted 18 May 2008 - 09:27 AM

Thanks for the answers... now I understand... but now I have ahother doubt ...

If I use an 85 mm on a s16 camera, Its like a 170 mm, but I have the same depht of field, no?

If it's a lens designed for s16, no. DoF is in part determined by the area of coverage of the lens. Namely, if the lens is designed to cover a smaller area (such as a S16 frame vs a 35mm frame) the DoF is greater, deeper. On the other hand, it is easier to manufacture larger apetures for smaller coverage circles, allowing for faster lenses. So, in your example, an 85mm f1.4 would give the same DoF as a 170mm f2.8 on a 35mm, roughly.
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#12 Larry Nielsen

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Posted 18 May 2008 - 12:56 PM

I'll add a few more confusing notes to this. I always here of tis and try to explain to the best of my knowledge, but some how confuse people even more, but her goes. there are different format leses, 16, 35, 65, 35 anamorphic, and so on. Most depth of field charts are based on 35mm spherical lenses, you can make your own for the format you're shooting, or just simply do the math in your head. depth of field is based on F stop, focal length, and distance to subject. Now I always say T stop, because in the motion picture industry thats what we work in, my old Samcine wheel has the difference between a F and a T stop as a one stop difference, my new one has them pretty darn close as no difference at all.

Part two of the equation is Field of view, Some people feel that a 35mm format lens on a 16mm camera has less depth of field. This of course is just the opposite, and I'll try to explain. The image used earlier shows the view of a 50mm lens in both the 16mm and 35mm formats, the 16mm view of course being the smaller image with in the 35mm frame. In order to achieve the larger image in the 16mm format, I would have to switch to a 25mm lens, and in order to achieve the smaller image in the 35mm format I would have to switch to a 100mm lens. These examples are just what they are, they are not mathematically correct. 16mm of course is not half of 35mm. A 50mm 35mm format lens on a 16mm camera translates to a 109 mm lens on a 35mm camera in order to achieve the same field of view. So now lets focus our attention back to the smaller image in the frame. Lets just say that the barn is 60 feet away from my film plane, and we're shooting at T 5.6 my depth on the 50mm is 26'11" to infinity, my depth on the 109mm is 47'8" to 80'8".

Now I use field of view loosely, because yes there is a difference in field of view from format to format, 35mm spherical 1:85, 2:35, 2:40, 1:78 and so on.
If both cameras 16mm, and 35mm had 1:33 ground glasses, this would pretty much stand up.

Now lets focus another situation using the image above again I have a 16mm camera with a 50mm, 35mm format lens on it, right next to it, I have a 35 mm camera with a duplicate 50mm lens on it. The Barn is 60 feet away, and my T stop is 5.6, Whats my depth of field?


Larry
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#13 Chris Keth

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Posted 18 May 2008 - 03:34 PM

If it's a lens designed for s16, no. DoF is in part determined by the area of coverage of the lens. Namely, if the lens is designed to cover a smaller area (such as a S16 frame vs a 35mm frame) the DoF is greater, deeper. On the other hand, it is easier to manufacture larger apetures for smaller coverage circles, allowing for faster lenses. So, in your example, an 85mm f1.4 would give the same DoF as a 170mm f2.8 on a 35mm, roughly.


The area of coverage is not even a variable in the equation to calculate depth of field, therefore it can not affect it in any way. The ONLY reason smaller formats tend to exhibit greater depth of field, given an equal final blowup size (which is how a proper CoC is determined), is the tendency to use wider lenses on that format.

Edited by Chris Keth, 18 May 2008 - 03:37 PM.

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