Use of zoom lenses on 3D shoots?

[Karel Bata]

I was under the impression that many 3D shoots employing a mirror rig use zoom lenses so they can 'dial in' a focal length and save on set-up time between shots.

 

However a stereographer I spoke to yesterday said he always uses primes because of the quality.

 

Which made me wonder what the preference out there generally is..?

 

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Edited June 23, 2010 by Karel Bata

[Alfeo Dixon]

Which made me wonder what the preference out there generally is..?

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Karel,

 

The preference is two identically matched lenses for ever sizing. Since most lenses are assembled by hand, even if they are consecutive in serial numbers, they may still be slight differences across the board. A zoom by nature is a variable lens, why on earth would you want to add more variables into your workflow.

 

-Alfeo

[Karel Bata]

Well, there are always slight differences between lenses.

 

Let me refer you to the section on zoom lenses in Bernard Mendiburu's book 3D Movie Making http://bit.ly/Zoom3D

 

If you're a steadicam operator then loading up your rig with two zooms would be a bit ridiculous. But I was wondering what other stereographers here thought about this..?

[James Neihouse]

Well, there are always slight differences between lenses.

 

Let me refer you to the section on zoom lenses in Bernard Mendiburu's book 3D Movie Making http://bit.ly/Zoom3D

 

If you're a steadicam operator then loading up your rig with two zooms would be a bit ridiculous. But I was wondering what other stereographers here thought about this..?

 

Zoom lenses add too many variables to the already complicated 3D equation. Any miss-match between the lenses focal lengths causes undue eyestrain in the viewer. For the best 3D, everything should match!

 

The primary reason for using zoom lenses on beam-splitter rigs is the reduction in lens change over time. Some of the beam-splitter rigs I have worked with take quite a long time to change lenses, so zooms are the easy answer. When choosing a rig always take into consideration the time required to switch lenses.

 

Most serious stereographers will tell you that you should never zoom in a shot, because zoom lenses do not track perfectly. One lens may deviate left and up while the other is deviating right and down. This is due to the complexity of the lens mechanical system that is need to move the optics facilitating the zoom.

 

Most all of the optical mismatch problems can be fixed in post, if you have the time and budget, but what if you're going out live?

 

James Neihouse

Director of Photography

IMAX Hubble 3D