The making of a lenticular picture
A lenticular picture is made from two components: a print and a lenticular sheet. These components have to be bonded together with a very high precision.
The print is composed from thin stripes arranged in cells. In the picture below each stripe is numbered and painted in a different color. A cell is a group of adjacent stripes which fills the space spanned by a single lenticule. In the picture below there are five stripes in a cell, but in real lenticular pictures this number is much larger, typically more than 10.
This type of print is called "interlaced image". It is made form a sequence of conventional images. Each stripe is a sample from one image in the sequence. In the picture below the interlaced image is created from a sequence of five images. For making a 3D lenticular picture the image sequence shows different perspectives of the displayed object.
The quality of a lenticular picture depends on the presize alignment of the print to the lenticules. Two independent parmeters must be controlled:
Parallelism: the stripes must be parallel to the lenticules,
Centering: the central cell must be centered with respect to the central lenticule.
Adjustment of parallelism is essential. Pictures with severe misalignments will not display the object over their whole area. Instead, the picture area will split onto two or more vertical zones, with discontinuous jump between them. Less severe misalignment will reduce the viewing angle. Both effetcs spoil the viewing experience.
Every lenticular picture has a certain viewing agle, which is determined by the optical properties of the lenticular lens. When the viewer crosses the boundaries of the viewing abgle he sees a discontinuous flip in the image. For best viewing experience the boundaries of the viewing angle should be symmetric with respect to the central viewing position. This is achieved by controlling the centering of the print relative to the lens (sometimes called "phasing").
In some printing techniques the print is deposited directly on the lens. In other techniques the print is done on paper with a standard printer, and then it is bonded to the lens. I currently use the second method.
The adjustment and bonding of the print to the lens are done manually. Therefore, in each picture there are small deviations from perfect alignment, and therefore every one is different.
Picture credit: "Lenticular-Stereogram" by Koperczak (talk) 14:30, 31 March 2009 (UTC) - self-made PhotoShop drawing. Licensed under Public domain via Wikimedia Commons
