Digital projectors like this small pico projector from Viewsonic are increasingly 3D ready so you can display games, movies and stills—usually with shutter glasses.
DepthQ modulators (Z-screens) in two sizes. Courtesy of www.depthq.com
A pair of alignment slides makes it easier to align the projector. Courtesy of studio3d.com
(DLP) projectors use a solid state chip like the one above, developed by Texas Instruments, that has hundreds of thousands or millions of tiny hinged mirrors on its surface. Light hitting a mirror tilted one way reflects through the projection lens to the screen. Light hitting a mirror tilted the other way reflects to a light absorber. By placing a spinning color filter wheel in between the light and the mirrors full-color images can be projected onto the screen. Courtesy of Texas Instruments.
EVGA's UV Plus+ uses any available USB port on your desktop or notebook computer and turns it into an additional video output for use with another display be it an LCD, CRT or Projector.
One of the ironies in digital photography is that although it makes it easier and less expensive to display images to millions of people one on one, it makes it more expensive to show them to small groups gathered around a TV set, or to room-sized groups. The days of the old lantern slide show are long gone and 35mm slide shows have recently followed them off stage. Slide shows are now given with a digital projector (sometimes called a multimedia projector) and screen. If you've ever slept through a PowerPoint presentation, that was the technology being used. Your show can be stored on any of the computer's storage devices and played from there, or fed to the projector from a TV or DVD/Blu-ray player. You can show anaglyphs with any screen and 2D projector, but for professional results you need a more elaborate system based around polarized glasses or, less frequently—shutter glasses.
Most 3D projectors employ Texas Instruments' (TI) Digital Light Processing (DLP) technology because of the technology's compatibility with the 3D video reproduction process.
Active Systems using Shutter Glasses
One of the most popular 3D setups uses a single DLP projector to alternately project left and right eye images that are viewed through shutter glasses. Since only one eye sees an image at any given time, and the glasses cut the light farther only 16% of the original projector light reaches the eye.
Passive Systems using Polarizing Glasses
There are a number of possible setups using polarizing filters over the projection lenses and in the viewer's glasses.
- Two DLP projectors can be used, each with a filter oriented at 90° to the other. The polarized images are viewed through inexpensive passive polarized glasses. The polarizing filters and glasses reduce the light so only 38% of the original projector light reaches the eye.
- Two LCD projectors use LCD panels to polarize the light passing through. The panels and polarizing glasses let through 59% of the original projector light—the most of any system.
- A Single projector with a Z-screen projects images sequentially while a Z-screen (or modulator) in front of the lens is synchronized so it polarizes the left and right images in each pair differently. Since only one eye is seeing projector light at any one time and both the Z-screen and viewer's glasses absorb some of the light, only 12% of the original projector light reaches the viewer.
WHAT ARE THE PERCENTAGES?
The percentages in this section referring to how much light reaches the viewers eyes are from Barco, leading suppliers of stereo projection systems (www.barco.com
Giving a Show
Unless you are giving corporate 3D shows, or have more money to spare than most of us, the most popular setup for large groups is two DLP projectors that project superimposed left and right images through polarizing filters onto a silver screen that are viewed with polarized glasses. Their biggest problem is that two projectors require careful registration of left and right eye views and both projectors must have the same brightness, focal length and other characteristics. If you want to try this do-it-yourself approach here is a summary of the things you will need and do.
- A pair of DLP projectors with a resolution between 1024 x 768 (XGA) and 1900 x 1200 (WUXGA). 2000 lumens should suffice but brighter is always better.
- Polarizing filters for each projector with a way to mount them in front of each lens without getting them so close the heat can affect them.
- An adjustable stand to make it easier to stack the projectors vertically (so their lenses are close together) and adjust their images so they are registered on the screen. These are hard to find because most new stands don't support two projectors. Your best bet may be to search eBay for a "Chief projector stand."
- Polarizing glasses for each member of the audience. These can be bought in quantity from a number of on-line dealers.
- A silver screen that preserves the polarization of the images as they reflect off it. A good source for silver screens is studio3d.com.
- Photo-edit Software, such as StereoPhoto Maker is needed to align your stereo pairs, adjust their stereo windows and save them side by side at twice the width of your projector's horizontal resolution. For example, if your projector's resolution is 1900 x 1200 each pair should be 3800 pixels wide and no higher than 1200. When projected through the two projectors, one half of the image will be through the left projector and the other half through the right.
Each projector has a native resolution—basically the number of pixels on its LCD panel or mirrors on its DLP chip. The projector can project larger images without degrading them, but images smaller than it's native resolution have to be enlarged and artifacts of that process show. For this reason, you might prepare your images for a higher resolution projector than you currently use. That way you won't have to redo them later if you get a projector with a higher resolution.
- Software to assemble the images that are to be shown. The programs that many stereo photographers use for this are Proshow Producer (www.photodex.com), MyAlbum (myalbum.com), Picture to Exe (wnsoft.com/) or even PowerPoint (www.microsoft.com) or Adobe Premier (www.adobe.com). These programs let you specify transitions between images but be sure to test the ones you choose—not all work equally well with stereo images.
- A laptop computer with dual video card or a DualHead-2Go from Matrox is needed to split the data being sent to the two screen into two streams, one for each monitor or each projector. Using software on the computer or that came with the DualHead2Go unit, set the screen so the right monitor (projector in our case) is an extension of the left one. (On Windows 7 systems you right-click the desktop to display a pop-up menu, select Screen resolution, then under Multiple displays select Extend these displays.) The screen is now one continuous 2800 strip so when you move your mouse horizontally and it reaches an inner border it jumps to the next screen.
Monitors and projectors have aspect rations of 1.33. This is calculated by dividing their resolutions height in pixels into the width in pixels. Most cameras do not capture images with an aspect ratio of 1.33 so when you edit them, make the height match the resolution of the projector and the width will take care of itself.
DualHead2Go by Matrox, displays your images on two monitors or two projectors. Courtesy of Matrox (www.matrox.com
High end computers have the ability to use two monitors at the same time.
Lasers, widely used to create images in printers and store ata on optical disks, may well be used to project 3D images on a screen.
A pair of projectors outfitted with polarizing filters and ready to give a 3D show. Courtesy of Reel 3-D Enterprises.