Lenticular Viewing Distance

Because lenticular images utilize a lens, there is an optimal viewing distance. For 3D images (those on vertical lenticules) a viewer significantly beyond the optimal viewing distance will not see any effect because the relative distance between the two viewing angles (the eyes) is null. For animation effects viewing beyond the viewing angle will significantly increase (or reduce to null) the amount of movement required to see the complete animation.

Depending on the type of display this becomes very important. Where viewers will be standing signifcantly far away (such as large billboard displays) there is no reason to create a lenticular as the effect will be lost and the cost and time associated with the medium will be wasted. The same goes for simply large displays, regardless of where the viewer is it may be impossible to get the same vantage point on the entire image. For larger displays such as movie posters this should be taken into consideration.

Other considerations regarding viewing distance will help to dictate the type of lens used. Lens sheets with a narrow viewing angle, typically saved for 3D effects to help give each eye a separate view, are more reliable for distance viewing as they reduce the amount of movement required to achieve the animation or 3d result. Large animation displays with narrow viewing angles can be placed strategically where viewers are apt to move through the complete range required, this can mean mounting an image above a ramp, stairwell, or escalator.

For more about lenticular see 3dEngr's 10 things lenticular.

Printing Lenticular on a Substrate and Attaching to Lens

As an alternative to printing directly on the lens interlaced images can be printing on a substrate and later adhered to a lens. The substrate must be a flat surface so that the lens is attached at a uniform distance, ensuring clean viewing. Printing on a substrate does have advantages, mainly, the ability to align an image to ensure a clean result. Even if a printer is not capable of holding a sheet securely for an aligned print trimming edges and centering to the lens can be done as a secondary process. Also, with some patience and precision it is possible to create a lenticular print with a known “jump” point. The point at which the lens focuses from the first image to the last image in a sequence. For media displays that require a viewer to walk past this means you can guarantee the start of an animation corresponds to the beginning of the viewing path. 

This redbull marketing video has a great sample of how to register an image to the lens (at 2:18 in the video)

There are plenty of places to buy raw lenticular sheets, which allows for the creation of 3D and animated lenticular by hobbyists. To get super high quality printing directly on the lens a high end printer is typically required.

For more about lenticular see 3dEngr's 10 things lenticular.

Printing on a Lenticular Lens

Printing can be on a substrate that is adhered to a lens or directly on the lens itself. When printing directly on the lens, the ink is applied to the flat side of the lenses. In this printing method it is important that the printer is capable of aligning the interlaced image directly with the lenses. This level of precision limits the number of printers capable, and to some extent the speed, of the print. If a sheet is fed through a printer at even the slightest angle the interlaced printed lines will not match the lenses and the result will be a jumbled mess with lots of ghosting and blurry images.

This video shows a high end printing putting down an image directly on a sheet.

For more about lenticular see 3dEngr's 10 things lenticular.

Stereoscopy for Lenticular

Drawing three dimensional images are difficult to create because of the inherent two dimensional nature of the drawing surface. Over years of refinement artists have found ways to depict three dimensional items in two dimensional mediums. Perspective, foreshortening,  and ocular occlusion are only a few examples. Different layers or depth of an image will move less through the field of vision of an observer. This means that objects at varying distances in the image shift differently across the many layers or angles of viewing used for the individual interlaced images.

The earliest forms of 3D imagery used stereoscopy, or two separate images each from a distinct view point, to create a feeling of depth. The slight variations between each image mimic what the human eyes see. The brain is great at interpreting both images at once and thus perceiving depth. A lenticular 3D creates the same effect and because each eye has a slightly different view point to the lens the light it sees will be from a different part of the image and because the source image is interlaced that means each eye sees an entirely different image. This allows the brain to do it's job of interpreting two images at once and perceiving depth.

There are multiple ways to create each angle of the image. The easiest is to physically take an image from multiple view points which can be done by setting up multiple cameras or a system that moves a camera in standard intervals. The Mitton rail system shown in the video on a previous post is one example of this. To manually create an image form a flat surface takes a bit more manipulation the workflow for which is shown in the below video.

Yet another way to create these images is to use a rending software of a digitally created scene. Software such as Solidworks Photoworks, or Blender can be setup to have multiple camera viewing angles. Each angle can be rendered separately and then interlaced to create stunning 3D of a digital scene. Those accustomed to macros and batch processes will notice that with a few key criterion (interlacing spacing, viewing distance, number of images) are all that is needed to easily create a interlaced image for home creation for nearly any rendered scene.

For more to look for in lenticular imagery return to 3DEngr's 10 things about lenticular.

Lenticular Image Interlacing

Lenticular gives a motion or 3D effect because the lens can be used to focus on distinct images, each in unison. Similar to a movie that has frame after frame of still images flashed quickly a raw lenticular image (viewed without the lens) will appear as if it is more than one image.

To create a lenticular first all the frames (for animations) or angles of viewing (3d) are created.Frames for 3D lenticular are organized and located typically in layers of a photoshop file or similar platform equivalent.  In the case of animations it is typical to have each image as a separate file, although users accostomed to creating easy aniommations in an image editing software such as Photoshop or GIMP may still prefer to store frames as layers. Software can then be used to separate thin slivers of each layer, layers are then reorganized. For a 3 frame sequence (Frames 1, 2, 3) each of the three images may be broken up into 5 slivers (A,B,C,D,E). They are then interlaced in the following sequence:

3D lenticular works on the same principle but instead of each image behind a different frame of animation it is a different angle of viewing for the same scene.

Assuming each sliver gets 1 pixel this means at a minimum the above example would be 15 pixels. However when broken into slivers the overall dimensions of the image are generally keep the same to avoid any distortion. The result is that each image is actually 1/5th of the quality to be expected from an equally sized non-interlaced image. This means that even if using high definition video or imagery some degradation is expected and normal. It is simply unrealistic to believe that a 40 frame animation on lenticular the size of a smartphone will ever compare to an LCD output display. For every 40 pixels the LCD can display the lenticular can only show 1, solely because of interlacing.
There are some softwares that will do the interlacing for you. I expect these are a good start but not a replacement for a world class digital artist that truly understands the intracacies of depth and perspective.

Lenticular Image Creator

Also available are a number of great blogs following digital artists focusing on 3D imagery.

Youtube is fantastic for explanations including this one that shows the whole process from initial picutre to final interlaced image.

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