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Archive for the ‘Lenticular Printing Process’ Category

The range of photographic media for photo-art reproduction has grown apace in recent years. For serious and occasional collectors alike, it pays to understand the differences in methodology, and the potential effect of acquisition prices and the investment value for the years ahead. Here are some key terms and the processes which apply to them

C-Type Prints

Darkroom/wet prints made from colour negatives or transparencies. Before digital technology, these were the prints we all received from the pharmacies from our holiday films. They were also produced in larger sizes for exhibitions. C-type prints are now archival and are still preferred by some photographers and collectors to digital art prints.

Fine-art digital prints, aka Giclee, Iris or Art inkjet prints

The most common way of producing collectable prints in the digital age, is by scanning the original negative, or balancing a digital file from a digital camera, and out-putting the image, usually retouched, on various media types using archival inks. The advantage is that very fine quality coated papers can be used to make delicate, beautiful prints. Rockarchive’s Edition 100 is made in this way in various sizes without any loss of quality.

Lamda or Lightjet

This mode of printing contains elements of both traditional darkroom printing and digital technology. The original negative is scanned, or a digital image adjusted, and the resulting image is outputted onto photographic paper by means of laser light. The prints have the same archival value as traditional photographic RC prints or C-type prints on plastic based papers, with the advantage to some collectors of being called ‘photographic prints’.

Lenticular

Lenticular printing is a multi-step process consisting of creating an image from at least two existing images, and combining it with a special lens. This process can be used to create various frames of animation (for a motion effect), or simply to show a set of alternate images which may appear to transform into each other.

The combined lenticular print will show two or more different images simply by changing the angle from which the print is viewed.

Other Print types

There are an array of differing print methods now available using both traditional and contemporary techniques.

Silk screen

A screen is made of a piece of porous, finely woven fabric (originally silk, but typically made of polyester since the 1940s) stretched over a frame of aluminum or wood. Areas of the screen are blocked off with a non-permeable material to form a stencil, which is a negative of the image to be printed; that is, the open spaces are where the ink will appear.

The screen is placed atop a substrate such as papyrus or fabric. Ink is placed on top of the screen, and a fill bar (also known as a flood bar) is used to fill the mesh openings with ink. The operator begins with the fill bar at the rear of the screen and behind a reservoir of ink. The operator lifts the screen to prevent contact with the substrate and then using a slight amount of downward force pulls the fill bar to the front of the screen. This effectively fills the mesh openings with ink and moves the ink reservoir to the front of the screen. The operator then uses a squeegee (rubber blade) to move the mesh down to the substrate and pushes the squeegee to the rear of the screen. The ink that is in the mesh opening is transferred by capillary action to the substrate in a controlled and prescribed amount, i.e. the wet ink deposit is equal to the thickness of the stencil. As the squeegee moves toward the rear of the screen the tension of the mesh pulls the mesh up away from the substrate leaving the ink upon the substrate surface.

Silver Gelatin fibre prints

Prints made from an original black & white negative in the darkroom using chemicals and fibre papers are known as silver gelatin fibre prints. These are the most valuable to collectors, particularly as this now historic method of print making, combined with the fragility of old negatives, mean the prints will be rare. One of the characteristics to these prints is that they do not always dry completely flat and may look a little “wavy” when framed due to the process in which they are made. They are also particularly sensitive to dampness in the air and need to be treated with extra care.

Silver Gelatin RC prints

A silver gelatine RC print refers to an image made on resin-coated paper. These prints are also made from negatives in the darkroom using chemicals, but on plastic-based papers which are easier than fibre papers to work with. They also have the added benefit of drying flat. However, RC prints can be less ‘rich’ in terms of tone and texture than traditional fibre prints.

With 3D being on the spotlight in 2010 for the big screens and TVs, advertising and marketing professionals are seeking ways to present 3D on 2D media.

Lenticular printing finds its way to fill this gap.  It is a way to present 3D effects on 2D printed media without the need for viewers to wear any glasses. A piece of plastic called lenticular sheet is used to direct light ray to different directions depending on the viewing angle. Since there is an about 5cm distance between human eyes so for whatever objects we see our left-eye and the right-eye automatically form two different viewing angles. It is this fact that human can see the world three dimensionally. On a lenticular sheet there are many lenticules and each lenticule serves as if a convex lens. With careful calibration and design, the lenticules can present different images to the left-eye and to the right-eye, hence give the human brain the illusion of 3D.

The notion of converting 2D to 3D is actually very simple if you understand the principle of binocular disparity as described in the last paragraph. But the process is somewhat problematical if there is no help from ad hoc lenticular printing design software. Basically the 2D picture needs to go through the layering process. The result is that objects on the 2D picture will be on different layers of a Photoshop file. Once the objects are layered, a plan view of how far the objects are displaced is then drawn. An imaginative line is then drawn between the background and the foreground to represent the focal plane. This is the plane where the left-eye and the right-eye are seeing the same image. With the focal plane and the objects in place, one will use basic high school geometry to find out how much each object should be moved to the left or to the right when it is projected to the focal plane if it is seen by the left-eye. The same procedure is then done for the right-eye. Once these tasks are done one should get two resultant pictures, i.e. one picture meant for the left-eye and one meant for the right-eye.

The two pictures are then sliced and merged in such a way that when covered by the lenticular sheet the left-eye picture will be seen by the left-eye and the right-eye picture will be seen by the right-eye. Photoshop CS4 and up has build-in lenticular design functions. But if you are using pre-CS4 versions of Photoshop you will need to create the interlacing stripes by yourselves. For those who care to know the fundamentals please refer to the 2D to 3D Conversion Tutorial found on vicgi.com. Otherwise using the built-in feature from Photoshop should do the job much easier. In either case, understanding of the principle of binocular disparity is the foundation and is of paramount importance.

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