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Field of view vs. perspective?


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#1 Leon Liang

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Posted 19 December 2015 - 11:57 AM

Hi everyone,

 

I came across this short PDF from Panavision (http://www.panavisio...pective (3).pdf) that explains how focal lengths work, and I found this on page 8...

 

Let’s assume that the central Field of View of human vision has an angle of about 45 degrees, with Perspective corresponding to roughly a 40mm lens. To get the same Field of View in Super 35 you need to shoot with a 27mm lens, or thereabouts, but then the perspective will feel a little exaggerated. To get a similar Field of View with a Dragon 6K, you would shoot with a 35mm, which is closer to 40mm and would yield a less exaggerated, more natural perspective. Of course the filmmaker may want to exaggerate the perspective with wider lenses, or flatten it with longer ones, nevertheless the relationship of Angle of View to Perspective remains different with bigger sensors than with Super 35.....Some Panavision engineers, and notably the late Tak Miyagishima, have stated that the “natural” Perspective of bigger formats is scalable: that shooting larger formats will seem more natural no matter what the focal length. In this view, shooting with a wide- angle lens is simply equivalent to moving closer to the subject, while shooting with a longer focal length is like moving farther away, but in both cases the relationship of Perspective to Field of View retains its “natural” feel.

 

...which made me very confused. What is the difference between field of view and perspective? If you were film a person's face with a 50mm lens on Super 35mm, would you get the same field of view but a "flatter" face if you filmed the face from the exact same angle and distance with a 75mm lens on Vistavision?

 

Thanks,

 

Leon Liang

 

P.S. Or maybe Panavision is putting a bit of false advertising in there to make filmmakers who don't fully understand how focal lengths work buy Primo 70 lenses. You never know.


Edited by Leon Liang, 19 December 2015 - 11:58 AM.

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#2 Brian Drysdale

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Posted 19 December 2015 - 12:13 PM

To change the perspective you have to change the camera position (or distance), just changing the focal length with a different lens is like zooming in, which doesn't change the perspective.


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#3 Mark Dunn

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Posted 19 December 2015 - 12:18 PM

Additionally, a wide-angle lens can introduce some distortion at the edges which may look like a change in perspective, but it isn't.


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#4 Leon Liang

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Posted 19 December 2015 - 12:20 PM

But then what do they mean by:

 

Of course the filmmaker may want to exaggerate the perspective with wider lenses, or flatten it with longer ones, nevertheless the relationship of Angle of View to Perspective remains different with bigger sensors than with Super 35.

 

My interpretation is that they're saying you will change the perspective if you use a sensor or film frame of a different size but using a lens with the same field of view.

 

To change the perspective you have to change the camera position (or distance), just changing the focal length with a different lens is like zooming in, which doesn't change the perspective.

 

That what my initial perception of "perspective" was, but now...not so sure.


Edited by Leon Liang, 19 December 2015 - 12:21 PM.

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#5 Stuart Brereton

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Posted 19 December 2015 - 12:30 PM

A 25mm lens at 10ft will give you the same field of view as a 50mm at 20ft, but the perspective will be different. The 25mm will give you a much wider view of the background behind the subject, whereas the 50mm will tend to slightly compress the foreground and background. If you were to then change to a 100mm lens at 40ft, you would again have the same field of view, but the perspective would change, and the backgrounds would be invent more compressed


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#6 Leon Liang

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Posted 19 December 2015 - 12:36 PM

I understand that using a wide lens close to the subject will give a different perspective from a long lens far from the subject, and that was my original understanding of perspective.

 

Right now I'm just confused about how using a larger format would affect the perspective; as in, if you shot a scene with a 40mm lens on Super 35mm, then shot the same scene with everything (hypothetically) the same, except now using a 60mm lens on full-frame 35mm, would the perspective change at all? Because the PDF seems to be saying that it does affect the perspective and I'm inclined to think it doesn't.


Edited by Leon Liang, 19 December 2015 - 12:37 PM.

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#7 Mark Dunn

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Posted 19 December 2015 - 01:47 PM

You're right, it doesn't. That assertion that the relationship between FoV and perspective is dependent on format is at best misleading and at worst plain wrong.


Edited by Mark Dunn, 19 December 2015 - 01:48 PM.

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#8 Leon Liang

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Posted 19 December 2015 - 02:35 PM

Thanks, that certainly clears things up.


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