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The Lenticular Imaging Process

Lenticular technology is a high resolution imaging process developed for the purpose of creating multi-imaging visual effects such as 3Dimensionality or animation.

This is achieved through four key elements of the production process.

1. Lenticular lens:

The lenticular plastic sheet is designed with a precise parallel array of lenticules or lenses. Each lens is capable of magnifying data which is aligned precisely underneath it. The lenticular plastic sheet is an optically clear stable substrate with a smooth reverse side surface allowing for the application of the appropriate image.

2. Digital art:

a. Origination: Any lenticular effect must be created from at least two complete in scale files. For example, a two image flip (clown smiling; clown frowning) starts out as two separate files. A lenticular animation can incorporate more files such as four, eight or twelve, which covers the sequence of the proposed animation. A lenticular 3dimensional image works best with at least twelve separate files covering the spectrum of the prospective 3dimensional environment.

b. Interlacing: The art must be divided precisely among all the lenses that make up the final lenticular image size. The original images are actually sliced to fit into spaces equal to the width of each lens. For example a two image flip would be made with one-half of all the lenses containing image no.1 while the other half of all the same lenses would contain image no.2. The process of interleaving the original files into the master which will match precisely to the pitch (number of lenses per inch) of the lens is called interlacing.

3. Output:

a. in lithographic printing the lenticular image is printed direct to the lenticular plastic lens. This would require films to be output from an image setter. This again is a high resolution process requiring precise calibration.

b. Other methods of reproduction are for example digital photographic or inkjet where the interlaced master is output as a finished image which then needs to be laminated to the reverse of the lenticular plastic sheet in a separate adhesive process.

4. Printing:

The most common method accounting for over 90% of the lenticular imaging in the world today is direct to lens lithographic printing. From high resolution films, plates can be exposed and positioned in precise register on a four colour process press. Most presses available in this category are in fact likely to be 6 colours, allowing a blanket background white to be printed in the same pass. Usually a more opaque white needs to added later after the inks are dry; there are many methods of doing this (UV ink, silk screen, laminated cover stock or thermal laminated polypropylene).

Prepress process:

Software:

* Photoshop
* Quark
* Illustrator

Memory (RAM)

* minimum we would recommend is 500MB which will be laborious, an Apple G5 would likely have 1GB which would be fine. Use maximum RAM on operating unit, and have additional Hard Drive as a scratch disk on the side.

Image setter:

* minimum 300 line screen to achieve reasonable quality, best quality is available using 400 line screen.
* at least 2540 DPI (Res 100), using 5080 DPI (Res 200) will deliver much higher quality results.

Film:

* standard film is .004" thick, while .007" film is recommended for dimensional stability. Note: When converting to .007 film from .004, the colour laser heads would need to be reset.

Proofing:

* we have found that 3M Imation match print system is the best. It is extremely stable whereas other systems such as Fuji are guaranteed to expand and contract requiring compensation. Commercial grade Imation paper is good while 'Low Gain' Imation stock is excellent, sometimes better than what is achievable on press.

Here for your review a description of the process of interlacing.

A. File Preparation:

Depending on the type of effect desired you will have determined the number of files you will create to illustrate this effect. For example, a basic flip (one image changing to another image) is simply two files. A lenticular animation can be any number of files ranging from two (a flip) to a recommended maximum of twelve depending on the type of action and the number of files which would work best for that animation. A lenticular morph is considered an animation and twelve would be appropriate. A lenticular 3D image would require at least twelve files to be minimally effective while we could recommend twenty files if your equipment could manage the data and outputs. Whatever the final number, all the files must be scaled to the exact same size and resolution before interlacing. Sufficient bleed must be built in especially for 3D where the viewing angle will require extra (horizontal) data. The minimal final resolution is determined by the three variables of a) the lenticular lens design, b) the number of files you are employing, and c) the output capability of your image setter. For example, a 75 LPI lens (75 lenticules per inch) employing a twelve file animation or 3D image would create a pixel count of 900 per inch (75 x 12 = 900). To transfer this digital data accurately to film and to plate and finally to the lens substrate, an accurate multiplier of 900 PPI (pixels per inch) must be found on the image setter (for example: 1800, 2700, 3600, 4500 DPI (dots per inch). Should an exact multiplier not be available on the image setter, you would first interlace your files to the highest resolution available on your files, and then the interlaced master could be 'res'd down' (reduce resolution) to match the output capability of the image setter. It is critical that the data (the pixels that are sourced from your files) fit precisely into the lens. By following these procedures you will be able to calibrate the data properly.

B. Interlacing:

This is the process of taking the data from the files and reorganizing it to fit precisely into the lenticules which make up the lens array of the lenticular sheet. It is best to explain this process with a simple example such as in the case of a basic flip. The technology of lenticular is based on the ability of the lens to magnify data which has been placed underneath it. There is room at the bottom of the lens to place a lot of data depending on the size (resolution) of that data. In the case of a basic lenticular flip we only need to put two bits of data, each representing one of the two images selected which make up our final animation (a two image flip). Since we have determined that the lens design we are planning to print to is a 75 LPI, we now know the width of the lens is one-seventy-fifths of an inch (.0133").

The two images of the flip must fit into this space, so we will create in Photoshop a mask which will alternately cut and save half a lenticule of data, and then block the other half lenticule of data. If the lenticule measures precisely .0133" wide, the mask will be made up of 'openings' and 'blocks' which measure half of this size or .00665" wide each. The mask is used to grab the desired data from image A and save it into a master file, then grab the desired data from image B and save it in the same master file next to image A. The master file is now complete, and in theory if this master file was output through the image setter, the resulting films (or match print proofs) could be layed under the lens and you would witness the flip working in alternate viewing positions.

There are many other procedures and elements which need to be understood and managed in the lenticular process. Please review the above and attempt to master these before moving on to the next steps in the process and contact The Lenticular Plastic Company for more information.

Source: LPC Lenticular Plastic Company of Europe www.lpc-europe.com