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3D Imaging Magic

Posted by caseycrockerphoto on April 22, 2010 at 6:16 PM

3D Imaging Magic


(written for Camren Photographic's November 2009 Newsletter)


Although the 1950s are most often considered the 3-D movie decade, the first feature length 3-D film, "The Power of Love," was made in 1922. Ever since, the use of 3-D technology in theaters and television has risen in popularity. Film-makers James Cameron and Steven Spielberg are currently pushing 3-D technology in Hollywood by assimilating motion-capture 3-D effects with 3-D viewing during the filming process. Surely, this will forever alter the movie-going experience. But, how does making something with two dimensions into an illusion of three dimensions work? The magic occurs during a combination of projection and those goofy looking glasses. Whether you have used 3-D glasses for a big screen or at home experience you have to admit 3-D glasses are fascinating. Considering they have such high entertainment value, it may be surprising how amazingly simple 3-D glasses are. Put 3-D specs on an all of the sudden they make the movie or television show look real and directly in the same space. Wearing 3-D glasses makes you feel like you are a part of the action. What is the past and the present of this technology? Where is this technology going? Why is the 3-D of today better than the 3-D of yesterday? The answer is simple–the color Green.


Be sure to click on the picture of the 3-D glasses above for a visual compliment to this article. The 3-D technology of today and yesterday differ in unique ways, but they are based on the same principles of how binocular vision operates. Most human beings and animals use what is known as binocular vision to perceive depth and see the world in the three dimensions of length, width, and height. The binocular vision system relies on the fact that we have two eyes, which are approximately three inches apart. This separation causes each eye to see the world from a slightly different perspective. The brain fuses these two views together because it understands the differences and uses them to calculate distance and create the sense of depth. For objects up to about 20 feet the binocular vision system lets someone easily tell with good accuracy how far away an object exists. If there are multiple objects in our field of view, we can automatically tell which is furthest and which is nearest and how far away and apart they are. The illusion of 3-D tricks the brain into believing that binocular vision is in effect.

If you look at the world with one eye closed you can still perceive distance, but accuracy decreases and a slower reliance on visual cues takes place. To see how much of a difference the binocular vision system makes have a friend toss you a ball and try to catch it while keeping one eye closed. Try the same exercise in a fairly dark room or at night. The difference binocular vision makes in catching the ball is even more noticeable.


If you have ever used a View-Master or a stereoscopic viewer you have seen the binocular vision system in action. In a View-Master or stereoscope the audience is presented with a pair of images, but each individual eye is presented with its own image. These two images slightly differ in point of view. Originally, the camera photographed the same scene from slightly different positions to create images known as a stereo pair. The images are directly viewable using a parallel lens device, like the View-Master, which allows each eye to only see its respective image. When shown the stereo pair simultaneously in the stereoscope the two images blend together and form a single three dimensional image.


In a movie theater the reason why you wear the classic 3-D glasses is to feed different images into your eyes just like a View-Master does. The screen actually displays two images and the glasses cause one of the images to enter one eye and the other to enter the other eye. There are two common systems for doing this: anaglyph and polarization.

The anaglyph 3-D method uses glasses that contain a red gel filter for one eye and a blue gel filter for the other. This is the classic 3-D experience. In this system two images are displayed on a screen through two projectors; one projecting in red and the other in blue (sometimes green, but this promotes discoloration even though it is more effective for depth. Cyan gels make a good compromise for color and depth). The gel filters on the glasses allow only one image to enter each eye. This may sound counter-intuitive, but the red gel allows only the blue light through and vice versa. In effect, the combination of the red projection and red gel block one another, admitting only the opposite into the eye. The same is true for the other eye. These glasses are called anaglyph glasses. You cannot really do justice to a color movie when you are this method because we actually see three colors; red, blue, and green. If one color is omitted, which anaglyph 3-D promotes, then a good third of the overall coloration of the picture is lost. The illusion of depth of field also weakens.


The polarization 3-D method incorporates glasses, but in a different way. This method is more commonly used in modern 3-D movie projections. Modern movie theaters do not project two images from two projectors with the polarization method. Rather, the images are already combined and the single lens is sending two signals with two opposing polarizations. The audience must then wear polarized glasses with lenses that transmit the light of the movie in a special way so that each eye receives a different type, or angle, of polarization. Each lens has its respective polarization directions adjusted to be 90 degrees different from one another. This makes is possible for the left eye to see its picture and does not allow light of another polarization to pass through. Vice versa is true for the right eye. Similar to the anaglyph system, each lens blocks the light meant for the other eye. This method is more effective because it allows all three colors of light to reach the eyes, which in turn makes the experience more real because the entire visible spectrum and all its colors and tones are present. This means the color green is no longer subtracted from the 3-D equation, like the anaglyph method. And the color green is a very special color to human depth perception.


Light consists of three colors: red, green, and blue. Together, in unison, the eye can see all humanly perceivable colors. Anaglyph 3D glasses do not give us quite the same effect because in using them we are only presented a pair colors to mix. Red in one eye and blue in the other. Some glasses used a red and cyan or red and green combination. Cyan is a half blue and half green mixture, so the eye is seeing both at the same time in one eye. This can make the image look red. If a green gel is used for a lens, then a green image mixes with a red, totally absent of blue, which generally results in a muddy, unpleasing color with qualities of gray. A rose filter in one eye and cyan for the other might solve this problem. However, because polarizational materials do not interfere with the perception of color, and they do actually enhance the dynamic range of a scene, they are the best bet in at home or large scale 3D image viewing.


The color green also has context with digital camera sensors. Large amounts of contrast and color depth are generated through the color green. Take a CCD or CMOS sensor and you will find that inside the mosaic color array that makes up the final picture are twice as many green pixels as there are red and blue combined. In a CCD or CMOS equipped digital camera half of the pixels are dedicated to the color green. The color green aides in depth perception, color transition, tonality, and therefore an impact on an image’s three- dimensionality. Simply put, green consists for a large share of the visible spectrum. Without the color green, old methods of 3-D trickery fall short and digital cameras wouldn’t be able to render scenes the way our eyes see. An amplification of this area of the spectrum is also why night vision works.

There are some more complicated systems as well, but because they are expensive they are not as widely used. For example, in one system, a TV screen displays the two images alternating one right after the other. Special LCD glasses, called shutter glasses, block the view of one eye and then the other in rapid succession. This system allows color viewing on a normal TV, but requires the purchase of specialized equipment.


While 3-D technology is impressive, some people still want a solution that does not require them to wear glasses. This is quite the challenge for motion pictures, however there is one way to create three-dimensional images in every day places. Movies often advertise with this system. This method relies on a display coated with a lenticular film. Lenticules are tiny lenses on the base side of a base layer. The screen displays two sets (or more) of the same image. The lenses direct the light from the images in a particular fashion so that each eye sees a single image. Since often, this system is used with more than one image, so that as the image is moved, different images are visible. This technology requires content providers to create special images for the effect to work. They must interlace two sets of images together. If you were to try and view the still or video feed on a normal screen nothing but a quilt-work of overlapping images would be seen.


As far as creating glasses-free movie experience, Sony is introducing a single lens 3D video camera for motion pictures. Based on their image separation design using a single lens is beneficial because the viewer could see a normal 2D movie without the use of glasses or have the option of a 3D experience. (More information on the camera’s design is available here: http://www.sony.net/SonyInfo/News/Press/200910/09-117E/index.html)


Fuji is also introducing a compact 3D camera with a twin-lens design, called the 3DW1, that allows the user to snap photos and video and view that image in 3D with the naked eye. The camera incorporates a dual-CCD image sensor technique to do so. Literally, the camera takes 2 pictures on 2 sensors. Though a lenticular screen might do the job, the camera also contains a special LCD screen that projects each image separately so each eye sees separate images, resulting in a 3D experience. The print method for these 3D images incorporates lenticular technology. (Information about the Fuji 3D W1 here: http://www.fujifilm.com/products/3d/camera/finepix_real3dw1/) No matter how it is considered, 3-D technology is still a very popular pursuit and is gaining future potential.

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Click here for illustrations:

http://www.camren.com/tech/11_11_09_3D.html?act=GetArticleAct&articleID=2326


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