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Anamorphics, rental houses and math (Oh MY!)


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#1 Jay Young

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Posted 08 February 2016 - 06:41 PM

So I called a rental house today, and talked to the rental manager.

 

I said, I want a 4-perf 35mm camera, and 40mm and 75mm anamorphic 2x. 

They said "you want 2.35:1?"  I said no, I want 2.66:1 I'm not going to crop the sides.

They said "So you want Super 35", I said no

They said "So you want 4:3", I said yes

 

It went on like this for some time, but finally the thing that made me just want to hang up the phone.

 

They said, "you realise that the 40 will act like an 80mm at 2x, and that 75mm is going to be really long like a 150mm"... Finally I just started saying YES so they would get me my quote.

 

Anyhow, I was under the impression that anamorphic glass acted like it's divided counterpart. 

 

That is, a 40mm anamorphic 2x lens would act like a 20mm on the u-squeeze horizontal plane, and like a 40mm on the vertical.   Is this not correct?  Did I miss something in 'I have an anamorphic lens in my hand right as I type this and it sure doesn't double the focal length at any point' school and get it wrong.

 

Someone reassure me that I think they were talking about crop factor or some crazy thing?!

 

I just need some reassurance, or some serious re-schooling on the optical properties of anamorphic lenses!


Edited by Jay Young, 08 February 2016 - 06:42 PM.

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#2 Satsuki Murashige

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Posted 08 February 2016 - 06:45 PM

Yes, you are correct. Sounds like the person you were talking was very confused.
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#3 Carl Looper

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Posted 08 February 2016 - 07:23 PM

Yes, you are correct. They have got it wrong.

 

The focal length is independant of angle of view. It is no more and no less than the distance between a lenses centre of projection and the film plane. It becomes the size of the film in the film plane, with respect to a given focal length which determines the actual angle of view. If the film size was infinitely large the angle of view would be 180 degrees (ignoring the crop which a lens circle introduces). In other words, without a film size, the lens angle of view is undefined. In short, lenses on their own, don't have an angle of view. One needs to know the film size in order to calculate angle of view.

 

Now between the lens and the film the 'angle of view' could be considered the same regardless of whether the lens was anamorphic or otherwise. But by angle of view we mean the content of the image (what we see of the depicted world) rather than just the angle of light between the lens and the film frame. In the case of anamorphic lenses the angle of view (of the outside world) is squeezed during photography and then unsqueezed during projection, and so the focal length/ film size relationship requires we include the anamorphic factor if we're to get what we normally mean by angle of view. In the case of a 2X anamorphic we would be seeing twice as wide as that which a non-anamorphic of the same focal length, on the same film size would be seeing.

 

 


Edited by Carl Looper, 08 February 2016 - 07:32 PM.

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#4 David Mullen ASC

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Posted 08 February 2016 - 07:34 PM

Well, they were sort of correct about Super-35... when you said that you wanted 2.66 instead of 2.35, that meant you wanted the lens centered for Super-35 because you were shooting Full Aperture, not Academy/Anamorphic aperture.

 

As for the field of view, maybe they though you meant you wanted a 2X extender on the lens, not that you wanted a 2X anamorphic (in other words, you probably should have just said you wanted anamorphic lenses and not confused them by saying "2X" even though that is correct.  The odds would be very low of them giving you anamorphic lenses that weren't 2X.)

 

But if they did understand regular anamorphic was what you wanted, then they are incorrect, a 40mm anamorphic behaves like a 20mm horizontally but a 40mm vertically.

 

Maybe they thought you wanted to rear-adapt spherical lenses with a 2X anamorphic element, which would double their focal length effectively (they'd use a 20mm spherical lens with a rear adaptor to get you a 40mm anamorphic lens equivalent.)

 

It would help if you mentioned to them up front the specific anamorphic lens you wanted, let's say a 40mm Cooke anamorphic.

 

The one issue you might run into with your plan is the groundglass, you'd want to use a 1.33 Full Aperture / Super-35 groundglass.


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#5 Jay Young

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Posted 08 February 2016 - 08:45 PM

Yes, thanks David.
I triend to explain an clearly as I could. Maybe I didn't do a good job.

The only reason I ever mentioned 2x is because they kept trying to get me to shoot 3-perf spherical, crop for 16x9 or use the 1.3x lenses. And in that particular conversation Super35 was mentioned as an alternative to "4x3"... It was very odd.

Maybe it was a case of not ordering an Alexa or something standard.

Anyhow, I'll double check the quote order and make sure it looks correct.
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#6 David Mullen ASC

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Posted 08 February 2016 - 09:16 PM

Just make sure:

 

the camera is 4-perf 35mm

the gate / lens is set for Super-35 Full Aperture

the groundglass is 1.33 Silent / Super-35 / see:

 

http://www.arrirenta...ormat_guide.pdf

You'd want the GG from page 27 or 36 (the one on page 27 is not available for the Arricam)

 

the viewfinder has an anamorphic desqueeze option

 

the lenses are 2X anamorphic

 

you may have to go for a 6x6 matte box on the 40mm

 

In terms of video tap, you may have to live with seeing a 2X squeeze though some monitors can switch this to letterbox -- ask the rental house

 

--

 

Shoot a framing chart for the telecine people


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Media Blackout - Custom Cables and AKS

Zylight

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Pro 8mm

The Slider

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Aerial Filmworks

Visual Products