|09 September 2017|
Intermediate 3d Modeler
Matching Lens and Camera FoV and Compression of 35mm Anamorphic Film in 3-D
Warning, there is a lot of technical information in this question , but for the sake of simplicity, I wanted to state the actual question here at the top, then all the details below.
What is the correct settings for a 3-D camera/lens if I want to match the compression of space and angle of view of a movie clip that was originally shot on 35mm film with a 2x anamorphic lens?
Would it be 22mm (actual width of film stock) or 44mm (since there is a 2x anamorphic).
I'm attempting to recreate an object from a movie (Yoda's Hut from Empire Strikes Back) and in order to get maximum accuracy (maybe a bit anal, but I digress) I am placing cameras around inside the 3D model of the Hut, and then modifying the geometry to match those shots.
Now I need to figure out the lenses used. Just judging by the look (and the fact they're shooting in a very tight space) I can tell that some of the shots are at least 30mm. So, in order to make everything match up with scale and depth, I need to figure out what the focal lengths of my virtual camera should be. Now, obviously it would be much easier if I just knew what lenses were used on what shots, but through much research, I have narrowed it down to the set of Panavision lenses that were used, and I'm reasonably sure that the focal lengths available to them were 30, 40, 50, 70mm. I've gotten conflicting information that says that a 20mm was available. It's not much information, but it's a starting place. But in order to narrow it down, I need to know my "sensor" size. I have tried both, and I just can't seem to make everything match up, so I'm afraid it's a product of having wrong sensor/film size, wrong focal length, or both, hence why I'm trying to figure out the scientific answer to this, so I know that I at least have the sensor size correct.
So, in my software (Blender, in this case) I have a sensor size option, and a focal length option for my camera. Empire was shot on 35mm film in the Panavision format (also known as standard modern anamorphic ) using a 22mm x 18.6mm area on the film stock, and then using a 2x anamorphic lens to get the 2.37:1 ratio.
So the actual "Sensor" size is 22mm x 18.6mm, however with the 2x anamorphic lens, they're squeezing in twice the horizontal information. Then of course, they desqueeze it with anamorphic lenses on the projectors, or in my case, I'm just working with 1920x816 images screenshoted from my Blue Ray.
"You may only get one chance, make sure you take it."
|04 April 2018|
At the end of the day what matter is the field of view ( FOV) of the camera ( the angle seen by the camera )
The FOV is defined by the focale and the sensor size.
So you can either double the width of your sensor but then you will have to double your focale number
Or half the height of your sensor and keep the focale as is.
But in your case you will have also to compensate for the lens distortion espacially if you want to model it. Unfortunately anamorphic lens got a big distortions. The only way to mesure it is to shoot a grid.
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