3D Tips

The second photo of a stereo pair must NOT be taken from a point closer to or farther from the subject than is the first. That is, keep your distance to the subject exactly the same for both photos. When you move sideways to take the second photo, take care to move exactly perpendicular to the line of sight to the subject. Failure to observe this rule will result in an aberration which cannot be corrected.

Why? To illustrate; suppose you are taking a photo of a bikini clad beauty holding a beach ball toward you. In the first picture you just can see her smile over the top of the ball and her . . . navel below the ball. If the second shot is taken slightly closer, you will obscure either her lips or her navel. The resulting stereo pair will have rivalries which cannot be corrected due to the missing image data.

Even small errors of this type will degrade your stereos and make them uncomfortable to view. This error is often the cause of images that just won't align properly.

Some persons suffer headaches and/or nausea while watching 3D movies. The most likely cause is that 3D movies are not true binocular seeing. In a real 3 dimensional setting, people look at a near object and their eyes converge on it. At the same time, each eye changes shape slightly to bring the object into sharp focus. These are two separate actions, but in most people they are coupled. That is, when the eyes converge, the focus is near, and when the eyes are less converged (sight lines almost parallel), the focus is far. This is not what happens in artificial 3D (movies).

In artificial 3D, such as in a 3D movie, the eyes still converge to see objects that seem near and converge less to see objects that seem farther away. But here's the problem; all the images in a movie are at a fixed distance . . . on the screen. The eyes must learn to focus at a constant distance while vergence changes rapidly to look at objects that seem to be at varying distances. Some people, particularly older people, cannot easily disassociate focus from vergence and consequently suffer considerable discomfort, including headaches and nausea.

There are several things you can do to minimize this miasma. First, sit as far as possible from the theater screen. Second, try to keep your attention (eyes) on those parts of the movie action which seem to you to be occurring roughly at the distance where you think the actual physical movie screen is located. Third, and certainly obvious, take a time-out now and then. You have 3 options. If you want to keep viewing the movie, this is the best option; close or cover 1 eye (with the glasses still on) and view the movie in 2D. Removing the glasses is not the best option as the image will be blurred. The last option is, of course, to just close your eyes. My experience is that near sighted persons (who use glasses to drive) have less trouble than far sighted persons (who use glasses to read).

If you can't view 3D movies without discomfort, don't worry that you are missing something. Many people find that 3D actually distracts their attention from the subject matter of a movie. Why? Because regular 2D focuses your attention by reducing sensory overload. People watching 3D movies often admit to losing track of the plot and missing dialog due to the increased sensory input . . . they become overly absorbed in the 3D effect itself. On the other hand, movies with no other substance are only good to watch in 3D.  😉

There is now a wonderful new option available; 2D glasses for 3D movies. You can buy these glasses online for watching Real-D 3D movies. Get a pair or two to take with you for your 3D challenged or intolerant friends and, ta-da! . . . they will convert the 3D movie into a normal 2D movie experience. They work because both lenses are polarized the same; thus both eyes see the same image. For a long time I used to make these for friends by knocking opposite lenses out of two pairs of Real-D 3D glasses and gluing the lenses back into the opposite pair.

A considerable misunderstanding exists about 3D movies and how they work. Lets clarify exactly what happens on the 3D movie screen by discussing the 3 primary types of 3D movies.

Anaglyph 3D movies. These require the red and blue (or red/green or red/cyan) glasses with which we are all familiar. Just exactly as is done in comic books, each frame of the movie contains both the left and the right views superimposed. Consequently, the movie appears to be a bit of a garish mess if viewed without the glasses. With the glasses on, one of the images cannot be seen through the red filter and the other cannot be seen through the blue filter. Each eye thus has its own perspective view and this then provides an artificial 3D similar to what we experience in the real world.

Anaglyph 3D movies must be projected onto the screens extra brightly to compensate for the light reduction caused by the red/blue filters. Worse, the colors in an anaglyph movie are unrealistic. In fact some colors cannot be used at all because they closely match the filters in the glasses, resulting in visual discomfort and headaches.

Shutter glasses 3D movies. This is the Imax type of 3D that requires the electronic headgear. In this version the view for the left eye is projected on the screen and then the view for the right eye. At no time are both images on the screen at the same time. Meanwhile, in the headgear, there is a clear screen over the eyes. The left and right halves of this screen can be made opaque or transparent by electrical stimulation. So, in perfect synchronization with the alternating images on the screen, the head gear blocks first one eye then the other. In this way the viewer sees with the left eye only the image intended for that eye and likewise the right eye sees only its appropriate image.

The colors in a shutter glass movie are normal and the result is spectacular. When viewed without glasses, the images on the screen are blurred. Closing one eye allows you to view the movie in 2D.

Polarized glasses 3D movies. These movies use the glasses with dark gray lenses. Polarized 3D movies have been around forever. In the 1950's such classics as The House of Wax were released in a linear polarized version. You can tell if 3D glasses are linear polarized by placing two pairs face-to-face and trying to look through them. Doing this should totally block the passage of light. Again, like the anaglyph movie, both images are projected simultaneously on the screen. Each frame of the movie contains two images . . . the image for the left eye and the image for the right eye but they are projected through oppositely polarized filters. Thus, the left eye sees only the image whose filter direction matches the filter over the left eye and likewise for the right eye.

A new version of polarized 3D, called Real-D, is now becoming the norm. It is almost the same, but uses a new type of polarized filtering called circular polarization. These are still dark gray glasses, but reversing two pairs face-to-face does not totally block all light.

With both types of polarized 3D, the colors are perfectly natural and the result is spectacular. When viewed without glasses, the images on the screen are blurred. Closing one eye allows you to view the movie in 2D.