#3D images using normal and very wide interaxial lens spacing
When shooting 3D images, the distance between the left and right lenses matters as it impacts both the useful depth of the image and how close your camera can be to primary objects without the objects appear to “pop out” in front of the screen.
The following photos are 3d “red/cyan” stereoscopic anaglyph images. The photos were taken using dual Lumix GH-2 cameras and processed in Stereomaker. The original 5k pixel wide images were uploaded to my video blog; click on the image to see larger image. Use your red/cyan 3D glasses to view these images.
First photo is of playground equipment using my standard 5 1/4″ interaxial spacing – that is the closest I can get the cameras together, and the lens was set to 42mm (on a micro four thirds camera that is the same as an 84mm lens on a full frame camera).
Notice that the line of trees well behind the playground equipment is all “in the distance” at the same plane. Not much 3D going on back there. This is due to the closer lens spacing.
For the following images, I used my “sliding rail” mount which is a home made mount that enables me to separate the lenses by more than 2 feet.
The effect of a wider lens separation is to create a sense of stereoscopic depth much deeper into the scene than is possible with a narrow lens separation. Think of it like this – suppose your two camera lenses (or your eyes) were on top of each other, in the exact same spot. You would not see any 3D effect as you’d have a 2D image. But move your lenses (or eyes) apart by a millimeter or two. Now you would begin to see some depth but only for objects very close to you. Distant objects would not be sufficiently different in the left and right views to give a 3D sense to them.
Now move the lenses (or your eyes) several inches or even a foot apart. The difference in the images, even at far distances, will now be noticeable.
A “normal” 3D camera might have lens spacing in the 1 and 1/2 to 2 1/2 inches range (similar to your eyes). This camera will produce useful depth at up to perhaps 200 feet. Beyond that, objects will tend to appear on a distant plane.
By increasing the interaxial base, we extend the depth into the distance. In these photos, with a long stereo baseline between the lenses, depth is extended out to easily 800 to 1,000 feet.
Why don’t we then just always use a wide lens separation? Because a wide separation has impacts on objects appearing closer to the camera. As a rough rule, the closest subjects in your scene should be about 30 times the distance between the lenses. For a 2 foot lens separation, that means the nearest objects should be at least 60 feet away.
By comparison, my normal 5 1/4″ separation enables objects down to less than 14 feet from the cameras. Consequently, lens width matters! For my Canon HF M301 video camera set up, lens spacing is 2 5/8″ and enables taking 3D images down to within about 7 feet of the subject.
In these images (some shot at 42mm m4/3ds) we still see depth at what is probably 800 to 1,000 feet. But note that I carefully avoided having anything, like a tree, appear in the foreground – it would have hurt your eyes with this lens spacing!