1. Vertical Orientation
Vertical lenticular lenses deliver separate images to the left and right eye of an observer.
With a vertically oriented lens focusing on a vertically interlaced series of images it is possible create a 3D effect by utilizing the human brain’s natural desire to fuse two images, each seen from the slightly different perspective of each eye, into a depth map of the scene.
A typical 3D piece of art will contain items at varying depths. From foreground to background the overlapping of the images help to enhance the 3D effect. As a user shifts their focus the perception is that each layer would shift accordingly. Just as a tree far away would not shift greatly in the field of vision of an observer, the background of the image will stay primarily static. Items that are closer in the field of depth will have less movement, but may also be required to appear more in focus.
Each interlaced layer is taken from a slightly different viewing angle. As a viewer shifts laterally they see each subsequent image as if they have just changed their perspective on the scene. This is why each lenticular surface has an optimal viewing distance. At such a distance the effect of the shift is in line with how much an observer has moved. That means if they shift their head 5 degrees they will be transitioned to an image that is from a perspective that is also 5 degrees different. The construction of the lens defines this viewing angle.
Some great resources for more knowledge
Glossary of lenticular terms.
Lenstar.org has a good overview of lenticular and is usually up on current trends.
And below a great youtube video (not mine) that helps to explain the principles.
Back to 3dEngr’s 10 Things about lenticular or go to #2 Horizontal Orientation