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Stereo 3-D Rules.


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#1 Cesar Rubio

Cesar Rubio
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Posted 28 September 2011 - 02:09 PM

There are a few basic and simple rules for good stereo 3-D photography (they apply to video as well).

THE 1/30 RULE:

The 1/30 Rule refers to that the Stereo Base or separation between lenses (from center to center) should be no more than 1/30 the distance of the NEAREST object to the camera lenses.

Example:

For a Normal Stereo Effect (Ortho Stereo) the Stereo Base is of 2.5" or 6.5cm (65mm). You multiply 6.5x30 and that gives you 195 cms Or 1.95mts.

So your nearest (not necessary the main) subject, has to be at least 1.95mts away from the 3-D camera lenses.


ORTHO STEREO:


Ortho Stereo refers to a normal view of things like we see them with our own eyes.

The Stereo Base (or interaxial) is the distance between lenses from center to center and must be 2.5" or 65mm (6.5cm)


HYPO STEREO:

Hypo Stereo Is not the same as Hyper Stereo, and actually is the opposite, scenes and objects appear to grow larger and is used to make appear normal objects or people like if they were bigger or giants. Other use for hypo stereo is to be able to record insects or tiny objects (Macro stereo work) In order to use hypo stereo properly, the 1/30 rule s a good starting point (usually with measurements in mm.)

For 3-D photography of inanimate objects and scenes usually 1 camera is used on a slide bar, changing positions for the second picture to be taken. For 3-D video, if the cameras are small enough to permit a side by side shooting it would be ok, if not, then a Beam Splitter rig must be used.

One of the 3-D movies that amazed me, was the IMAX movie Bugs 3D, where they were able to film tiny insects in 3-D. That was never been done before, and it was a breakthrough achievement by a team led by Peter Parks.

HYPER STEREO:


Hyper Stereo derivates from the Greek prefix "hyper" that means above or beyond, and in 3-D use is achieved by increasing the stereo base (distance between lenses) to make distant objects or scenes appear with sufficient depth, in order to have the correct stereo base you have to take into account the 1/30 rule to have a proper 3-D effect.

In 3-D photography this can be achieved with a single camera and successive exposures (for inanimate objects or scenes), or with 2 cameras (spaced some distance apart) and fired simultaneously.

There are 2 ways of interpreting a hyper stereo picture or video, one is to think of the observer as a giant looking at a smaller world. The other way is to think of the scene as a shrinked model of the real scene.


Now, in real world use how can I apply such rules?

It would be great if we could use Ortho Stereo (65mm SB) with a 35mm Focal Length (in FF 35mm photography) all the time just like the Stereo Realist camera used, but its impractical for all kind of shootings, so we have to combine all stereo techniques.


For FULL LENGHT shots of people I use a wide 30mm lens approximately (in terms of FF 35mm photography, so you have to make calculations for your lens format) . In the 2/3” format that would be something like a 8.5mm lens.

To get a full length view of people I need to be at least 3 mts. away from my main subject, so applying the 1/30 Rule the Stereo Base must be 100mm (3mts/30=0.1mts or 10cms).

For MID SHOTS I use a normal lens (16mm in the 2/3” format) with an Ortho Stereo base (65mm) so my main subject need to be at 1.95 mts from my camera lenses. (6.5x30=195 or 1.95 mts).

For CLOSE UPS I can use a 25mm lens (again in the 2/3” format) and use a narrower Stereo Base to avoid too much frame separation and get closer to my subject. My subject being at 1 mt away from my camera lenses with a 33mm Stereo Base will do the trick. (1/30=0.033) . And without compressing the background too much.

Cesar Rubio.
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