Creating 3-D Red/Blue Anaglyphs from Photographs
The ability to create 3-D images is currently a hot marketing tool as new technology has sparked interest in three dimensional media. One of the oldest and least expensive methods to create and reproduce a 3-D image is the anaglyph. Anaglyphs are a method of encoding a three-dimensional image in a single picture by superimposing a pair of pictures. The anaglyph consists of a left and right image encoded to create the perception of depth in the image. Anaglyphs are not difficult to create, however creating good anaglyphs is a craft. A poorly made anaglyph can make the viewer feel uncomfortable. The most important and difficult part of the anaglyph is creating the original photographs or images. The originals should have depth in the image; otherwise the anaglyph will not exhibit much 3-D effect. Objects in the foreground of the original photographs will create the appearance of depth or accentuate the 3-D effect.
The original images should be bright and ideally not have much red. With the red/cyan-blue anaglyph glasses, the right eye sees blue and green, the left eye sees gray. What about red? Red is absent, some light leakage through the glasses’ filters may produce limited red, and professional anaglyph designers go to great lengths to tweak the color channels to produce some resemblance of red, but this will never approach commercial quality color. Black and white or duotone anaglyphs can be used to compensate for problems with color reproduction shortcomings, especially reds in memory colors.
Original photo-fluorescent pink geranium
Simulation of loss of red in anaglyph viewed thorough red-cyan glasses, gray balance is better in the 3-D anaglyph.
A stereo camera with two lenses that captures both left and right images simultaneously in the exact same plane is the preferred method to create the left and right images for the anaglyph. A single lenses camera can be used if mounted on a tripod with a slide that enables the same image to be photographed several inches apart. With a single lens/image camera, the subject can not move between images. A limitation to the single lenses/image camera is anything that moves including people, pets, and clouds which will produce an unusable stereo image. The last method is free hand, where the photographer tries to hold the camera exactly the same and only shifts a couple of inches to the right for the second image. This method is unreliable and may require many attempts to produce a useable left and right image.
There are software programs that automatically combine the left and right images to form the anaglyph. Instructions to manually create anaglyphs in Photoshop are in a link at the end of this discussion. Some software will take a single image and split the channels to create a 3-D image. The quality of the single image anaglyph varies as the parallax or stereo effect is the same for the foreground and background and is not as good a left/right image anaglyph. In Photoshop a very basic anaglyph can be made from a single image by moving the red channel slightly to the left. Anaglyph software will take the left and right images, adjust the color for the proper channel, combine the left, and right images into a half or full anaglyph and can automatically align and rotate the images to the correct orientation. Some alignment is necessary when using a one-lens/camera system. StereoPhoto Maker software is a popular free download that will create several different types of 3-D images. StereoPhoto Maker has an auto-alignment feature that works well to position “free hand” created images. StereoPhoto Maker will keep the same file resolution and sizes of the original. http://stereo.jpn.org/eng/stphmkr/
Anaglyph with good depth.
Red/blue, or red/cyan glasses are needed to view an anaglyph. The red/blue lens are somewhat better filters, but the red-cyan produce somewhat brighter color at the cost of more ghosting as they are not as pure filters. Red/cyan is the most common anaglyph. Some eye-related medical conditions prevent some people from seeing 3-D anaglyphs. The glasses are available with low cost paper frames or higher quality plastic frames and better lenses.
Red/blue, red/cyan glasses to view anaglyph
The greater the distance between the left and right images, the greater the parallax, the more pronounced the depth of the 3-D effect. The subject matter in the foreground of the anaglyph will have the least amount of parallax or even a reverse parallax. The background or more distant subject matter will have the most parallax. Anaglyphs of distant subjects require more distance between the left and right images, closer subject matter requires less distance between the left and right images, reducing the amount of parallax in the anaglyph. The effect of the parallax in the anaglyph when viewed without the red/cyan glasses, in printer’s terms, looks like the image is significantly out of register.
The greater the amount of parallax, the greater or more pronounced the ghosting problem. Ghosting in anaglyphs is a common problem when some light is not completely filtered and is visible in the wrong channel/eye. Ghosting is similar to what printers call hue error in printing. The ghost appears as a grey or dark shadow that is part of the parallax or misregister. RGB LCD monitors with their greater color gamut, have more pure colors and tend exhibit less ghosting than a CMYK print. A printer producing a CMYK anaglyph should be aware of the ghosting issue and carefully proof the anaglyph. Some ghosting is inevitable, and the ghosting may not be that noticeable or objectionable. When creating the left and right photographs, the greater the distance between the left and right images, the greater the parallax and the potential for objectionable ghosts. Anaglyph software allows the adjustment of the position of the left/right images and ghosting can be somewhat reduced by decreasing the amount of parallax.
The circled areas in the parallax of this anaglyph will show a ghost in a CMYK print that is not visible on an LCD monitor
Another phenomenon that detracts from the quality of an anaglyph is a difference in the brightness/luminance of the left and right image. This creates a phenomenon referred to as retinal rivalry. Retinal rivalry may cause parts of the image to shimmer and cause the viewer more discomfort when viewing the anaglyph. Retinal rivalry is common when using a single lens camera as the brightness of the left and right image can vary, or when attempting to do color corrections with the left and right images. Right and left images adjusted in Photoshop should maintain their same brightness/luminosity. Color correction to increase the visible red in the anaglyph often creates retinal rivalry.
There is more information about creating anaglyphs, professional anaglyph designers, and image galleries posted on the Internet. Here are a couple of interesting links:
How to make a camera-mounted slide bar: http://wwwschra.mmel.org/stereo-photo-slidebar.php?l=en
Discussion of anaglyphs: http://nzphoto.tripod.com/sterea/anaglyphs.htm#ghost
Glasses to view anaglyphs: http://www.3dglassesonline.com/
Printing Industries web site: Seven-Minute Solutions PDF about creating an anaglyph in Photoshop.http://www.printing.org/sites/default/files/seven_minute/3-d_image_printing_crash_course.pdf