or 0.7%
Therefore the Native Parallax of a 30 foot screen is 0.7%, so we should make sure to keep our
maximum positive parallax under 0.7% of screen width if we plan to show our footage on a 30 foot
wide screen. If we shoot for a 65” 3DTV, then we can get away with over 3% positive parallax.
The 1/30th Rule
The 1/30 rule refers to a commonly accepted rule that has been used for decades by hobbyist
stereographers around the world.
It basically states that the interaxial separation should only be
1/30
th
of the distance from your camera to the closest subject.
In the case of ortho-stereoscopic
shooting that would mean your cameras should only be 2.5” apart and your closest subject should
never be any closer than 75 inches (about 6 feet) away.
Interaxial x 30 = minimum object distance
or
Minimum object distance ÷ 30 = Interaxial
If you are using a couple XF305 cameras in a side by side rig as
close as they will
fi
t together (6 inches) then the calculation would
look like: 6” x 30 = 180 inches or 15 feet.
That’s right… 15 feet!
But does the 1/30 rule apply to all scenarios? No, the 1/30 rule
certainly does not apply to all scenarios.
In fact, in feature
fi
lm
production destined for the big screen we will typically use a ratio
of 1/60, 1/100 or higher.
The 1/30 rule works well if your
fi
nal
display screen size is less than 65 inches wide, your cameras were
parallel to each other, and your shots were all taken outside with
the background at in
fi
nity.
When you are ready to take the next
step to becoming a stereographer you will need to learn about
parallax range and the various equations available to calculate
maximum positive parallax (the parallax of the furthest object,)
which will translate into a real-world distance when you
eventually display your footage.
Remember that illustration on page 3 of the eyes pointing outward (diverging)?
Well it isn’t natural
for humans to diverge and therefore the maximum positive parallax when displayed should not
exceed the human interocular of 2.5 inches (65mm.)
You can readjust the convergence point and
bring the maximum positive parallax within the limits of the native display parallax (2.5 inches) but
that will also increase your negative parallax.
XF300/305 Whitepaper
Stereoscopic 3D
Tim Dashwood
7
Summary of Contents for XF105
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